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Pediatrics_Nelson. yet identified) also seemto play a role because there is often nonconcordance amongmonozygotic twins. It is possible that viral infections can initiate the inflammatory process. Dietary triggers are unproven.Smoking doubles the risk of CD and halves the risk for UC.


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Pediatrics_Nelson. Clinical manifestations depend on the region of involvement. UC involves only the colon, whereas CD can include the entire gut from mouth to anus. Colitis from either condition results in diarrhea, blood, and mucus in the stool; urgency; and tenesmus, a sensation of incomplete emptying after defecation. When colitis is severe, the child often awakens from sleep to pass stool. Toxic megacolon is a life-threatening complication characterized by fever, abdominal distention and pain, massively dilated colon, anemia, and low serum albumin owing to fecal protein losses. Symptoms of colitis always are present in UC and usually suggest the diagnosis early in its course. Extraintestinal manifestations of UC occur in a few patients and may include primary sclerosing cholangitis, arthritis, uveitis, and pyoderma gangrenosum (Table 129-1).


Pediatrics_Nelson

Pediatrics_Nelson. Symptoms can be subtle in CD. Small bowel involvement in CD is associated with loss of appetite, crampy postprandial pain, poor growth, delayed puberty, fever, anemia, and lethargy. Some symptoms may be present for some time before the diagnosis is made. Severe CD with fibrosis may cause partial or complete small bowel obstruction. Perineal abnormalities, including skin tags and fistulas, are another feature distinguishing CD from UC. Other extraintestinal manifestations of CD include arthritis, erythema nodosum, and uveitis or iritis. Blood tests should include complete blood count, albumin,erythrocyte sedimentation rate, and C-reactive protein(Table 129-2). Anemia and elevated platelet counts are typical. Testing for abnormal serum antibodies can be helpfulin diagnosing IBD and in discriminating between the colitis of CD and UC. Antineutrophil cytoplasmic antibody is found in about 66% of UC patients and in only a few CD


Pediatrics_Nelson

Pediatrics_Nelson. Malaise, fever, weight loss Common Common Rectal bleeding Sometimes Usual Abdominal mass Common Rare Abdominal pain Common Common Perianal disease Common Rare Ileal involvement Common None (backwash ileitis) Strictures Common Unusual Fistula Common Very rare Skip lesions Common Not present Transmural Involvement Usual Not present Crypt abscesses Variable Usual Intestinal granulomas Common Rarely present Risk of cancer* Increased Greatly increased Erythema nodosum Common Less common Mouth ulceration Common Rare Osteopenia at onset Yes No Autoimmune hepatitis Rare Yes Sclerosing cholangitis Rare Yes *Colonic cancer, cholangiocarcinoma, lymphoma in Crohn’s disease.


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Pediatrics_Nelson. cases. Anti–Saccharomyces cerevisiae antibody is presentin about 50% of CD patients and is uncommon in UC. MoreIBD-specific antibodies are being developed and include anti-OmpC, directed against an Escherichia coli membrane protein, and anti-CBir1, directed against bacterial flagellin,among others. Because there is overlap between CD and UC, none of these tests can discriminate absolutely between the two conditions.


Pediatrics_Nelson

Pediatrics_Nelson. In patients with suspected IBD, an upper GI series with small bowel follow-through is often used to detect small bowel involvement. Colonoscopy is preferred over contrast enemabecause biopsy specimens can be obtained and because visualfeatures can be diagnostic. Findings in UC include diffuse carpeting of the distal or entire colon with tiny ulcers and loss of haustral folds. Within the involved segment, no skip areas arepresent. In CD, ulcerations tend to be much larger with a linear,branching, or aphthous appearance; skip areas are usually present. Upper endoscopy cannot evaluate the jejunum and ileum,but is more sensitive than contrast studies in identifying proximalCD involvement. Other methods to detect small bowel involvement include video capsule endoscopy; computed tomography (CT) scanning, which can detect small bowel disease as well as abscesses; and MR enterography, which has the advantage of noradiation and good sensitivity for finding active bowel disease.


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Pediatrics_Nelson. UC is treated with the aminosalicylate drugs, which deliver 5-aminosalicylic acid (5-ASA) to the distal gut. Because it is CBC with WBC Anemia, elevated platelets suggest IBD differential ESR Elevated in many, but not all, IBD patients C-reactive protein Elevated in many, but not all, IBD patients Albumin May be low in IBD due to fecal loss ASCA Found in about 50% of CD patients and few UC patients Atypical p-ANCA Found in most UC patients and few CD patients Anti-OmpC Found in some UC and CD patients, rare in non-IBD Anti-C Bir1 Found in about 50% of CD patients Upper GI series with Evaluate for ileal and jejunal CD SBFT CT scan Used to detect abscess, small bowel involvement Tagged WBC scan Sometimes helpful in determining extent of disease Magnetic Resonance Used to detect bowel thickening, Enterography inflammation, and strictures as well as Upper endoscopy Evaluate for CD of esophagus, stomach, and duodenum; obtain tissue for histologic diagnosis


Pediatrics_Nelson

Pediatrics_Nelson. Upper endoscopy Evaluate for CD of esophagus, stomach, and duodenum; obtain tissue for histologic diagnosis Colonoscopy Show presence or absence of colitis and terminal ileal CD; obtain tissue for histology Video Capsule Emerging role in diagnosis of small bowel endoscopy CD, more sensitive than upper GI series with SBFT Anti-OmpC, Antibody to outer membrane protein C; ASCA, anti– Saccharomyces cerevisiae antibody; atypical p-ANCA, atypical perinuclear staining by antineutrophil cytoplasmic antibody; CBC, complete blood count; CD, Crohn’s disease; ESR, erythrocyte sedimentation rate; GI, gastrointestinal; IBD, inflammatory bowel disease; SBFT, small bowel follow- through; WBC, white blood cell.


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Pediatrics_Nelson. rapidly absorbed, pure 5-ASA (mesalamine) must be specially packaged in coated capsules or pills or taken as a suppository to be effective in the colon. Other aminosalicylates (sulfasalazine, olsalazine, and balsalazide) use 5-ASA covalently linked to a carrier molecule. Sulfasalazine is the least expensive, but side effects resulting from its sulfapyridine component are common. When aminosalicylates alone cannot control the disease, steroid therapy may be required to induce remission. Whenever possible, steroids should not be used for long-term therapy. An immunosuppressive drug, such as 6-mercaptopurine or azathioprine, is useful to spare excessive steroid use in difficult cases. More potent immunosuppressives, such as cyclosporine or anti–tumor necrosis factor (TNF) agents such as infliximab may be used as rescue therapy when other treatments fail. Surgical colectomy with ileoanal anastomosis is an option for unresponsive severe disease or electively to end chronic symptoms and to


Pediatrics_Nelson

Pediatrics_Nelson. may be used as rescue therapy when other treatments fail. Surgical colectomy with ileoanal anastomosis is an option for unresponsive severe disease or electively to end chronic symptoms and to reduce the risk of colon cancer, which is increased in patients with UC.


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Pediatrics_Nelson. Inflammation in CD typically responds less well to aminosalicylates; oral or IV steroids are more important in inducing remission. To avoid the need for repetitive steroid therapy, immunosuppressive drugs, usually either azathioprine or 6-mercaptopurine, are often started soon after diagnosis. CD that is difficult to control also may be treated with subcutaneous methotrexate or with agents that block the action of TNF-α. Infliximab is the most effective such drug and is given intravenously. Other antibodies that inhibit white blood cell (WBC) migration or action, such as natalizumab, also show promise. As with UC, surgery is sometimes necessary, usually because of obstructive symptoms, abscess, or severe, unremitting symptoms. Because surgery is not curative in CD, its use must be limited, and the length of bowel resection must be minimized.


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Pediatrics_Nelson. Celiac disease is an injury to the mucosa of the small intestine caused by the ingestion of gluten (a protein component)from wheat, rye, barley, and related grains. Rice does notcontain gluten and can be eaten freely, as can special purepreparations of oats not contaminated by other grains. In itssevere form, celiac disease causes malabsorption and malnutrition. Diagnosis was based on the presence of typicalsymptoms, followed by small bowel biopsy. The availabilityof more sensitive and specific serologic testing has revealedmany patients with few or no gastrointestinal symptoms whohave early, attenuated, or latent disease. Approximately 1 in110 persons in the United States have celiac disease, but onlya small proportion have been diagnosed. The disease is seenin association with type 1 diabetes, thyroiditis, Turner syndrome, and trisomy 21. Available @ StudentConsult.com Diarrhea Pubertal Delay Failure to Thrive


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Pediatrics_Nelson. Available @ StudentConsult.com Diarrhea Pubertal Delay Failure to Thrive Symptoms can begin at any age when gluten-containingfoods are given. Diarrhea, abdominal bloating, failure to thrive,irritability, decreased appetite, and ascites caused by hypoproteinemia are classic. Children may be minimally symptomaticor may be severely malnourished. Constipation is found in a fewpatients, probably because of reduced intake. A careful inspection of the child’s growth curve and evaluation for reducedsubcutaneous fat and abdominal distention are crucial. Celiac disease should be considered in any child with chronic abdominal complaints. Extraintestinal manifestations include osteoporosis, pulmonary hemorrhage, seizures/encephalopathy,dermatitis herpetiformis, and erythema nodosum.


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Pediatrics_Nelson. Serologic markers include IgA antiendomysial antibody and IgA tissue transglutaminase antibody. Because IgA deficiency iscommon in celiac disease, total serum IgA also must be measured to document the accuracy of these tests. In the absence ofIgA deficiency, either test yields a sensitivity and specificity of95%. An endoscopic small bowel biopsy is essential to confirm the diagnosis and should be performed while the patient is stilltaking gluten. The biopsy specimen shows various degrees ofvillous atrophy (short or absent villi), mucosal inflammation,crypt hyperplasia, and increased numbers of intraepitheliallymphocytes. When there is any question about response totreatment, a repeat biopsy specimen may be obtained severalmonths later. Other laboratory studies should be performed torule out complications, including complete blood count, calcium, phosphate, vitamin D, iron, total protein and albumin,and liver function tests. Mild elevations of the transaminases are common and should


Pediatrics_Nelson

Pediatrics_Nelson. out complications, including complete blood count, calcium, phosphate, vitamin D, iron, total protein and albumin,and liver function tests. Mild elevations of the transaminases are common and should normalize with dietary therapy.


Pediatrics_Nelson

Pediatrics_Nelson. Treatment consists of complete elimination of gluten from the diet. Consultation with a dietitian experienced in celiac disease is helpful, as is membership in a celiac disease support group. Lists of prepared foods that contain hidden gluten are particularly important for patients to use. Starchy foods that are safe include rice, soy, tapioca, buckwheat, potatoes, and (pure) oats. Many resources also are available via the Internet to help families cope with the large changes in diet that are required. Most patients respond clinically within a few weeks with weight gain, improved appetite, and improved sense of well-being. Histologic improvement lags behind clinical response, requiring several months to normalize. SEE CHAPTER 34.


Pediatrics_Nelson

Pediatrics_Nelson. SEE CHAPTER 34. Intussusception is the “telescoping” of a segment of proximalbowel (the intussusceptum) into downstream bowel (the intussuscipiens). Most cases occur in infants 1 to 2 years old; in this age group, nearly all cases are idiopathic. Viral-induced lymphoidhyperplasia may produce a lead point in these children. In olderchildren, the proportion of cases caused by a pathologic leadpoint increases. In young children, ileocolonic intussusceptionis common; the ileum invaginates into the colon, beginning at ornear the ileocecal valve. When pathologic lead points are present,the intussusception may be ileoileal, jejunoileal, or jejunojejunal. Available @ StudentConsult.com


Pediatrics_Nelson

Pediatrics_Nelson. An infant with intussusception has sudden onset of crampy abdominal pain; the infant’s knees draw up, and the infant cries out and exhibits pallor with a colicky pattern occurring every 15 to 20 minutes. Feedings are refused. As the intussusception progresses, and obstruction becomes prolonged, bilious vomiting becomes prominent, and the dilated, fatigued intestine generates less pressure and less pain. As the intussuscepted bowel is pulled further and further into the downstream intestine by motility, the mesentery is pulled with it and becomes stretched and compressed. The venous outflow from the intussusceptum is obstructed, leading to edema, weeping of fluid, and congestion with bleeding. Third space fluid losses and “currant jelly” stools result. Another unexpected feature of intussusception is lethargy. Between episodes of pain, the infant is glassy-eyed and groggy and appears to have been sedated. A sausage-shaped mass caused by the swollen, intussuscepted bowel may be palpable


Pediatrics_Nelson

Pediatrics_Nelson. is lethargy. Between episodes of pain, the infant is glassy-eyed and groggy and appears to have been sedated. A sausage-shaped mass caused by the swollen, intussuscepted bowel may be palpable in the right upper quadrant or epigastrium.


Pediatrics_Nelson

Pediatrics_Nelson. The diagnosis depends on the direct demonstration of bowelwithin-bowel. A simple way of showing this is by abdominalultrasound. If the ultrasound is positive, or if good visualization has not been achieved, a pneumatic or contrast enemaunder fluoroscopy is indicated. This is a potentially useful wayto both identify and treat intussusception. Air and barium canshow the intussusception quickly and, when administered withcontrolled pressure, usually can reduce it completely. The success rate for pneumatic reduction is probably a bit higher thanhydrostatic reduction with barium and approaches 90% if donewhen symptoms have been present for less than 24 hours. Thepneumatic enema has the additional advantages over barium ofnot preventing subsequent radiologic studies and having no riskof causing barium peritonitis if perforation occurs. Nonoperative reduction should not be attempted if the patient is unstableor has evidence of pre-existing perforation or peritonitis.


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Pediatrics_Nelson. Therapy must begin with placement of an IV catheter and a nasogastric tube. Before radiologic intervention is attempted, the child must have adequate fluid resuscitation to correct the often severe dehydration caused by vomiting and third space losses. Ultrasound may be performed before the fluid resuscitation is complete. Surgical consultation should be obtained early as the surgeon may prefer to be present during nonoperative reduction. If pneumatic or hydrostatic reduction is successful, the child should be admitted to the hospital for overnight observation of possible recurrence (risk is 5% to 10%). If reduction is not complete, emergency surgery is required. The surgeon attempts gentle manual reduction but may need to resect the involved bowel after failed radiologic reduction because of severe edema, perforation, a pathologic lead point (polyp, Meckel diverticulum), or necrosis.


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Pediatrics_Nelson. Appendicitis is the most common surgical emergency in childhood. The prevalence of appendicitis varies by age with the peak between the ages of 10 and 12 years. It is much less common in children under the age of 5. Appendicitis begins with obstruction of the lumen, most commonly by fecal matter (fecalith), but appendiceal obstruction also can occur, secondary to hyperplasia of lymphoid tissue associated with viral infections or rarely the presence of neoplastic tissue, such as an appendiceal carcinoid tumor. Trapped bacteria proliferate and begin to invade the appendiceal wall, inducing inflammation and secretion. The obstructed appendix becomes engorged, its blood supply is compromised, and it finally ruptures. The entire process is rapid, with appendiceal rupture usually occurring within 48 hours of the onset of symptoms. Available @ StudentConsult.com


Pediatrics_Nelson

Pediatrics_Nelson. Classic appendicitis begins with visceral pain, localized to the periumbilical region. Nausea and vomiting occur soon after, triggered by the appendiceal distention. As the inflammation begins to irritate the parietal peritoneum adjacent to the appendix, somatic pain fibers are activated, and the pain localizes to the right lower quadrant. Examination of the patient reveals a tender right lower quadrant. Voluntary guarding is present initially, progressing to rigidity, then to rebound tenderness with rupture and peritonitis. These classic findings may not be present, especially in young children or if the appendix is retrocecal, covered by omentum, or in another unusual location. Clinical prediction rules have been developed for the diagnosis of appendicitis. The Alvarado/MANTRELS rule is scored by 1 point for each of the following: migration of pain to the right lower quadrant, anorexia, nausea/vomiting, rebound pain, temperature of at least 37.3°C, and WBC shift to greater than 75%


Pediatrics_Nelson

Pediatrics_Nelson. scored by 1 point for each of the following: migration of pain to the right lower quadrant, anorexia, nausea/vomiting, rebound pain, temperature of at least 37.3°C, and WBC shift to greater than 75% neutrophils; 2 points are given for each of tenderness in the right lower quadrant and leukocytosis greater than 10,000/μL. Children with a score of 4 or less are unlikely to have appendicitis; a score of 7 or greater increases the likelihood that the patient has appendicitis. When classic history and physical examination findings are present, the patient is taken to the operating room. When doubt exists, imaging is helpful to rule out complications (right lower quadrant abscess, liver disease) and other disorders, such as mesenteric adenitis and ovarian or fallopian tube disorders. If the evaluation is negative and some doubt remains, the child should be admitted to the hospital for close observation and serial examinations.


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Pediatrics_Nelson. The history and examination are often enough to make the diagnosis, but laboratory and imaging studies are helpful when the diagnosis is uncertain (Table 129-3). A WBC count greater than 10,000/mm3 is found in 89% of patients with appendicitis and 93% with perforated appendicitis. This criterion is met by 62% of abdominal pain patients without appendicitis. Urinalysis is done to rule out urinary tract infection, and x-rays of the chest or the kidney, ureter, and bladder (KUB) rule CBC with differential Urinalysis Amylase and lipase ALT, AST, GGT Flat and upright abdominal radiographs (KUB) Abdominal ultrasound CT scan of abdomen ALT, Alanine aminotransferase; AST, aspartate aminotransferase; CBC, complete blood count; CT, computed tomography; GGT, γ-glutamyltransferase; KUB, kidney, ureter, bladder. *Perform when diagnosis remains in doubt.


Pediatrics_Nelson

Pediatrics_Nelson. out lower lobe pneumonia masquerading as abdominal pain. Amylase, lipase, and liver enzymes are done to look for pancreatic or liver and gallbladder disease. The plain abdominal x-ray may reveal a calcified fecalith, which strongly suggests the diagnosis. When these studies are inconclusive, imaging is indicated with an abdominal ultrasound or CT scan, which may reveal the presence of an enlarged, thick-walled appendix with surrounding fluid. A diameter of more than 6 mm is considered diagnostic. Treatment of appendicitis is surgical. Simple appendectomy iscurative if performed before perforation. With perforation, a course of postoperative IV antibiotics is required. Broad-spectrumcoverage is necessary to cover the mixed bowel flora.


Pediatrics_Nelson

Pediatrics_Nelson. Cholestasis is defined as reduced bile flow and is characterized by elevation of the conjugated, or direct, bilirubin fraction. This condition must be distinguished from ordinary neonatal jaundice, in which the direct bilirubin is never elevated (see Chapter 62). Neonatal jaundice that is secondary to unconjugated hyperbilirubinemia is the result of immature hepatocellular excretory function or hemolysis, which increases the production of bilirubin. When direct bilirubin is elevated, many potentially serious disorders must be considered (Fig. 130-1). Emphasis must be placed on the rapid diagnosis of treatable and potentially imminently lethal disorders, especially biliary atresia and metabolic disorders, such as galactosemia or tyrosinemia. Available @ StudentConsult.com


Pediatrics_Nelson

Pediatrics_Nelson. Available @ StudentConsult.com The jaundice of extrahepatic biliary atresia (biliary atresia) usually is not evident immediately at birth, but develops in the first week or two of life. The reason is that extrahepatic bile ducts are usually present at birth, but are then destroyed by an idiopathic inflammatory process. Aside from jaundice, these infants do not initially appear ill. The liver injury progresses rapidly to cirrhosis; symptoms of portal hypertension with splenomegaly, ascites, muscle wasting, and poor weight gain are evident by a few months of age. If surgical drainage is not performed successfully early in the course (ideally by 2 months), progression to liver failure is inevitable.


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Pediatrics_Nelson. Neonatal hepatitis is characterized by an ill-appearing infantwith an enlarged liver and jaundice. There is no specific diagnostic test. If liver biopsy is performed, the presence of hepatocytegiant cells is characteristic. Cytomegalovirus, herpes simplexvirus, and syphilis must be ruled out. Hepatobiliary scintigraphy typically shows slow hepatic uptake with eventual excretionof isotope into the intestine. These infants have a good prognosis overall, with spontaneous resolution occurring in most.


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Pediatrics_Nelson. α1-Antitrypsin deficiency presents with clinical findings indistinguishable from neonatal hepatitis. Only about 10% to 20% of all infants with the genetic defect exhibit neonatal cholestasis. Of these affected infants, about 20% to 30% develop chronic liver disease, which may result in cirrhosis and liver failure. Life-threatening α1-antitrypsin deficiency occurs in only 3% to 5% of affected pediatric patients. α1-Antitrypsin deficiency is the leading metabolic disorder requiring liver transplantation.


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Pediatrics_Nelson. Alagille syndrome is characterized by chronic cholestasis with the unique liver biopsy finding of paucity of bile ducts in the portal triads. Associated abnormalities in some (syndromic) types include peripheral pulmonic stenosis or other cardiac anomalies; hypertelorism; unusual facies with deep-set eyes, prominent forehead, and a pointed chin; butterfly vertebrae; and a defect of the ocular limbus (posterior embryotoxon). Cholestasis is variable but is usually lifelong and associated with hypercholesterolemia and severe pruritus. Progression to end-stage liver disease is uncommon. Liver transplantation sometimes is performed electively to relieve severe and uncontrollable pruritus.


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Pediatrics_Nelson. The laboratory approach to diagnosis of a neonate with cholestatic jaundice is presented in Table 130-1. Noninvasive studies may aid a rapid diagnosis. Early imaging studies are performed to evaluate for biliary obstruction and other anatomic lesions that may be surgically treatable. When necessary to rule out biliary atresia or to obtain prognostic information, liver biopsy is a final option (Fig. 130-2). Treatment of extrahepatic biliary atresia is the surgical Kasai procedure, in which the fibrotic extrahepatic bile duct remnant


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Pediatrics_Nelson. Treatment of extrahepatic biliary atresia is the surgical Kasai procedure, in which the fibrotic extrahepatic bile duct remnant Positive Coombs Negative Coombs Gilbert syndrome Alagille syndrome Hepatitis A, B, C, Progressive familial Total parenteral Idiopathic neonatal Autoimmune test test Physiologic Nonsyndromic D, E, G intrahepatic nutrition hepatitis chronic hepatitisABO and Rh RBC enzyme jaundice of the paucity of Cytomegalovirus cholestasis Acetaminophen Familial benign Sclerosingincompatibility defect (G6PD newborn intrahepatic bile Herpes simplex Wilson disease Ethanol recurrent cholangitis Autoimmune, deficiency) Breast milk ducts 1, 2, 6 ˜1-Antitrypsin Salicylates cholestasis Graft versus host systemic lupus Hemoglobinopathy jaundice Biliary atresia Epstein-Barr virus deficiency Cholestasis with disease Figure 130-1 Differential diagnosis of jaundice in childhood. G6PD, Glucose-6-phosphate dehydrogenase; RBC, red blood cell. AST, ALT Hepatocellular injury


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Pediatrics_Nelson. Figure 130-1 Differential diagnosis of jaundice in childhood. G6PD, Glucose-6-phosphate dehydrogenase; RBC, red blood cell. AST, ALT Hepatocellular injury Very long chain fatty acids Zellweger syndrome, peroxisomal disorders Abdominal ultrasound Choledochal cyst, gallstones, mass lesion, Caroli disease Percutaneous liver biopsy Biliary atresia, idiopathic giant cell hepatitis, α1-antitrypsin deficiency ALT, Alanine aminotransferase; AST, aspartate aminotransferase; CF, cystic fibrosis; GGT, γ-glutamyltransferase; RBC, red blood cell. Laboratory studies No diagnosis Specific diagnosis Abdominal ultrasound Biliary cyst or obstruction No biliary lesions seen Hepatobiliary scan Excretion into bowel Liver biopsy Surgery Evidence of biliary atresia No evidence of biliary atresia Specific therapy (if available), or Supportive care No excretion Figure 130-2 Flow chart for evaluation of neonatal cholestasis.


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Pediatrics_Nelson. Figure 130-2 Flow chart for evaluation of neonatal cholestasis. is removed and replaced with a roux-en-Y loop of jejunum.This operation must be performed before 3 months of age tohave the best chance of success. Even so, the success rate is low; many children require liver transplantation. Some metabolic causes of neonatal cholestasis are treatable by dietarymanipulation (galactosemia) or medication (tyrosinemia);all affected patients require supportive care. This includesfat-soluble vitamin supplements (vitamins A, D, E, and K)and formula containing medium-chain triglycerides, whichcan be absorbed without bile salt–induced micelles. Choleretic agents, such as ursodeoxycholic acid, may improve bileflow in some conditions. SEE CHAPTER 113.


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Pediatrics_Nelson. SEE CHAPTER 113. Fulminant liver failure is defined as severe liver disease with onset of hepatic encephalopathy within 8 weeks afterinitial symptoms, in the absence of chronic liver disease.Etiology includes viral hepatitis, metabolic disorders, autoimmune hepatitis, ischemia, neoplastic disease, and toxins(Table 130-2). Available @ StudentConsult.com


Pediatrics_Nelson

Pediatrics_Nelson. Available @ StudentConsult.com Liver failure is a multisystem disorder with complex interactions among the liver, kidneys, vascular structures, gut, central nervous system (CNS), and immune function. Hepaticencephalopathy is characterized by varying degrees ofimpairment (Table 130-3). Respiratory compromise occursas severity of the failure increases and requires early institution of ventilatory support. Hypoglycemia resulting fromimpaired glycogenolysis and gluconeogenesis must be prevented. Renal function is impaired, and frank renal failure, or hepatorenal syndrome, may occur. This syndrome ischaracterized by low urine output, azotemia, and low urinesodium content. Ascites develops secondary to hypoalbuminemia and disordered regulation of fluid and electrolytehomeostasis. Increased risk of infection occurs and may cause death. Esophageal varices may cause significant hemorrhage, whereas hypersplenism from portal hypertensionmay produce thrombocytopenia.


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Pediatrics_Nelson. Coagulation tests and serum albumin are used to followhepatic synthetic function. These tests are confounded byadministration of blood products and clotting factors. Vitamin K should be administered to maximize the liver’s abilityto synthesize factors II, VII, IX, and X. In addition to monitoring prothrombin time and partial thromboplastin time,many centers measure factor V serially as a sensitive index ofsynthetic function. Renal function tests, electrolytes, serum Neonatal hemochromatosis Electron chain transport defects Disorders of fatty acid oxidation Galactosemia Tyrosinemia Hereditary fructose intolerance Bile acid synthesis disorders Shock, hypotension Congestive heart failure


Pediatrics_Nelson

Pediatrics_Nelson. Shock, hypotension Congestive heart failure Hepatitis virus A, B Echovirus Coxsackievirus Adenovirus Parvovirus Cytomegalovirus Sepsis Herpes simplex ammonia, blood counts, and urinalysis also should be followed. In the setting of acute liver failure, liver biopsy maybe indicated to ascertain the nature and degree of injury andestimate the likelihood of recovery. In the presence of coagulopathy, biopsy must be done using a transjugular or surgicalapproach. Because of the life-threatening and complex nature of this condition, management must be carried out in an intensive care unit at a liver transplant center. Treatment of acute liver failure is supportive; the definitive lifesaving therapy is liver transplantation. Supportive measures are listed in Table 130-4. Alert and awake Agitated and distractible Infants and young children—irritable and fussy Normal reflexes Tremor, poor handwriting Obeys age-appropriate commands


Pediatrics_Nelson

Pediatrics_Nelson. Alert and awake Agitated and distractible Infants and young children—irritable and fussy Normal reflexes Tremor, poor handwriting Obeys age-appropriate commands Confused and lethargic Combative or inappropriate euphoria Hyperactive reflexes Asterixis present Purposeful movements, but may not obey commands Stuporous but arousable Sleepy Incoherent speech Motor response to pain Hyperreflexic Hyperventilation Asterixis present Unconscious, not arousable Unresponsive or responds nonpurposefully to pain Reflexes hyperactive Irregular respirations Pupil response sluggish Efforts are made to treat metabolic derangements, avoid hypoglycemia, support respiration, minimize hepatic encephalopathy, and support renal function.


Pediatrics_Nelson

Pediatrics_Nelson. Efforts are made to treat metabolic derangements, avoid hypoglycemia, support respiration, minimize hepatic encephalopathy, and support renal function. Chronic liver disease in childhood is characterized by thedevelopment of cirrhosis and its complications, and byprogressive hepatic failure. Causative conditions may becongenital or acquired. Major congenital disorders leading to chronic disease include biliary atresia, tyrosinemia,untreated galactosemia, and α1-antitrypsin deficiency. In older children, hepatitis B or C virus, autoimmune hepatitis, Wilson disease, primary sclerosing cholangitis, cystic encephalopathy Lactulose via nasogastric tube—start with 1-2 mL/kg/day, adjust dose to yield several loose stools per day Rifaximin or neomycin Enemas if constipated Mechanical ventilation if stage III or IV Coagulopathy Fresh frozen plasma only if active bleeding, monitor coagulation studies frequently Platelet transfusions as required


Pediatrics_Nelson

Pediatrics_Nelson. Coagulopathy Fresh frozen plasma only if active bleeding, monitor coagulation studies frequently Platelet transfusions as required Hypoglycemia IV glucose supplied with ≥10% dextrose solution, electrolytes as appropriate Ascites Restrict fluid intake to 50%-60% maintenance Restrict sodium intake to 0.5-1 mEq/kg/day Monitor central venous pressure to maintain adequate intravascular volume (avoid renal failure) Renal failure Maintain adequate intravascular volume, give albumin if low Diuretics Vasoconstrictors Dialysis or hemofiltration Exchange transfusion Liver transplantation fibrosis, and biliary obstruction secondary to choledochalcyst are leading causes. Available @ StudentConsult.com


Pediatrics_Nelson

Pediatrics_Nelson. Chronic liver disease is characterized by the consequences of portal hypertension, impaired hepatocellular function, and cholestasis. Portal hypertension caused by cirrhosis results in risk of gastrointestinal bleeding, ascites, and reduced hepatic blood flow. Blood entering the portal vein from the splenic and mesenteric veins is diverted to collateral circulation that bypasses the liver, enlarging these previously tiny vessels in the esophagus, stomach, and abdomen. Esophageal varices are particularly prone to bleed, but bleeding also can occur from hemorrhoidal veins, engorged gastric mucosa, and gastric var-ices. Ascites develops as a result of weeping of a high-pressure ultrafiltrate from the surfaces of the viscera and is at risk of becoming infected (spontaneous bacterial peritonitis); ascites can often be massive and interfere with patient comfort and respiration. The spleen enlarges secondary to impaired splenic vein outflow, causing excessive scavenging of platelets and


Pediatrics_Nelson

Pediatrics_Nelson. ascites can often be massive and interfere with patient comfort and respiration. The spleen enlarges secondary to impaired splenic vein outflow, causing excessive scavenging of platelets and white blood cells; this increases the patient’s susceptibility to bleeding and infection.


Pediatrics_Nelson

Pediatrics_Nelson. Impaired hepatocellular function is associated with coagulopathy unresponsive to vitamin K, low serum albumin, elevated ammonia, and hepatic encephalopathy. The diversion ALT, Alanine aminotransferase; AST, aspartate aminotransferase; CBC, complete blood count; CF, cystic fibrosis; ERCP, endoscopic retrograde cholangiopancreatography; GGT, γ-glutamyltransferase; HBeAg, hepatitis B early antigen; HBsAg, hepatitis B surface antigen. Serum α1-antitrypsin level α1-Antitrypsin phenotype if low serum level Serum ceruloplasmin Sweat chloride, CF gene tests if CF suspected Testing for other specific conditions as indicated by HBsAg Hepatitis B viral DNA, HBeAg if HBsAg positive Hepatitis C antibody Hepatitis C antibody confirmatory test if positive Hepatitis C viral RNA, genotype if antibody confirmed Prothrombin time and partial thromboplastin time Serum ammonia CBC with platelet count *Perform when indicated to obtain specific anatomic information.


Pediatrics_Nelson

Pediatrics_Nelson. Prothrombin time and partial thromboplastin time Serum ammonia CBC with platelet count *Perform when indicated to obtain specific anatomic information. of portal blood away from the liver via collateral circulation worsens this process. Malaise develops and contributes to poor nutrition, leading to muscle wasting and other consequences. Chronic cholestasis causes debilitating pruritus and deepening jaundice. The reduced excretion of bile acids impairs absorption of fat calories and fat-soluble vitamins, which contributes to the poor nutritional state. Deficiency of vitamin K impairs production of clotting factors II, VII, IX, and X and increases the risk of bleeding. Vitamin E deficiency leads to hematologic and neurologic consequences unless corrected.


Pediatrics_Nelson

Pediatrics_Nelson. Laboratory studies include specific tests for diagnosis of the underlying illness and testing to monitor the status of the patient. Children presenting for the first time with evidence of chronic liver disease should have a standard investigation (Table 130-5). Monitoring should include coagulation tests, electrolytes and renal function testing, complete blood count with platelet count, transaminases, alkaline phosphatase, and γ-glutamyltransferase at appropriate intervals. Frequency of testing should be tailored to the pace of the patient’s illness. Ascites fluid can be tested for infection by culture and cell count and generally is found to have an albumin concentration lower than that of serum.


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Pediatrics_Nelson. Serum albumin AST, ALT, GGT, alkaline phosphatase Total and direct bilirubin Serum cholylglycine or bile acids Serum cholesterol Ultrasound examination of liver and bile ducts Doppler ultrasound of hepatic vessels* Magnetic resonance cholangiography* Magnetic resonance angiography of hepatic vessels* Percutaneous or endoscopic cholangiography* Liver biopsy* Ultrasound of liver, pancreas, and biliary tree Consider magnetic resonance cholangiography or ERCP if evidence of biliary process Liver biopsy—as required for diagnosis or prognosis Height, weight, skinfold thickness 25-Hydroxyvitamin D level Vitamin A level Vitamin E level Prothrombin time and partial thromboplastin time before and after


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Pediatrics_Nelson. Height, weight, skinfold thickness 25-Hydroxyvitamin D level Vitamin A level Vitamin E level Prothrombin time and partial thromboplastin time before and after Treatment of chronic liver disease is complex. Supportive carefor each of the many problems encountered in these patientsis outlined in Table 130-6. Ultimately, survival depends on theavailability of a donor liver and the patient’s candidacy for transplantation. When transplantation is not possible or is delayed,palliative procedures, such as portosystemic shunts, can beconsidered. The transjugular intrahepatic portosystemic shuntis an expandable stent placed between the hepatic vein and abranch of the portal vein within the hepatic parenchyma. Thisprocedure is performed using catheters inserted via the jugularvein and is entirely nonsurgical. All portosystemic shunts carryincreased risk of hepatic encephalopathy. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com Table 130-6 Management of Chronic Liver Disease PROBLEM CLINICAL MANIFESTATIONS DIAGNOSTIC TESTING TREATMENT Gastrointestinal variceal bleeding* Hematemesis, rectal bleeding, melena, anemia CBC, coagulation tests, Doppler ultrasound, magnetic resonance angiography, endoscopy Somatostatin (octreotide) infusion, variceal band ligation or sclerotherapy, propranolol to reduce portal pressure, acid-blocker therapy, TIPSS or surgical portosystemic shunt if transplant not possible CBC, Complete blood count; TIPSS, transjugular intrahepatic portosystemic shunt; WBC, white blood cell. *May also have peptic ulcerations.


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Pediatrics_Nelson. Wilson disease is characterized by abnormal storage of copper in the liver, leading to hepatocellular injury, CNS dysfunction, and hemolytic anemia. It is an autosomal recessive trait caused by mutations in the ATP7B gene. The encoded protein of this gene functions as an ATP-driven copper pump. The diagnosis is made by identifying depressed serum levels of ceruloplasmin, elevated 24-hour urine copper excretion, the presence of Kayser-Fleischer rings in the iris, evidence of hemolysis, and elevated hepatic copper content. In any single patient, one or more of these measures may be normal. Clinical presentation also varies, but seldom occurs before age 3 years. Neurologic abnormalities may predominate, including tremor, decline in school performance, worsening handwriting, and psychiatric disturbances. Anemia may be the first noted symptom. Hepatic presentations include appearance of jaundice, spider hemangiomas, portal hypertension and its consequences, and fulminant hepatic failure.


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Pediatrics_Nelson. disturbances. Anemia may be the first noted symptom. Hepatic presentations include appearance of jaundice, spider hemangiomas, portal hypertension and its consequences, and fulminant hepatic failure. Treatment consists of administration of copper-chelating drugs (penicillimine or trientine), with monitoring of urine copper excretion at intervals. Zinc salts often replace chelating agents after chelation therapy has successfully reduced excessive body copper stores. Adequate therapy must be continued for life to prevent liver and CNS deterioration.


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Pediatrics_Nelson. Immune-mediated liver injury may be primary or occurin association with other autoimmune disorders, such as inflammatory bowel disease or systemic lupus erythematosus.Diagnosis is made on the basis of elevated serum total IgGand the presence of an autoantibody, most commonly antinuclear, anti–smooth muscle, or anti–liver-kidney microsomal antibody. Liver biopsy specimen shows the presence ofa plasma cell–rich portal infiltrate with piecemeal necrosis.Treatment consists of corticosteroids initially, usually withthe addition of an immunosuppressive drug after remissionis achieved. Steroids are tapered gradually as tolerated tominimize glucocorticoid side effects. Many patients require lifelong immunosuppressive therapy, but some may be able tostop medications after several years under careful monitoringfor recurrence.


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Pediatrics_Nelson. Steatohepatitis, also known as nonalcoholic fatty liver disease or nonalcoholic fatty hepatitis, is characterized by the presence of macrovesicular fatty change in hepatocytes on biopsy. Varying degrees of inflammation and portal fibrosis may be present. This disorder occurs in obese children, sometimes in association with insulin-resistant (type 2) diabetes and hyperlipidemia. Children with marked obesity, with or without type 2 diabetes, who have elevated liver enzymes and no other identifiable liver disease are likely to have this condition. Nonalcoholic fatty liver disease can progress to significant fibrosis. Treatment is with diet and exercise. Vitamin E may have some benefit. Efforts should be made to control blood glucose and hyperlipidemia and promote weight loss. In general, the rate of progression to end-stage liver disease is slow.


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Pediatrics_Nelson. The cause of inadequate pancreatic digestive function in 95%of cases is cystic fibrosis (see Chapter 137). The defect in CFTR chloride channel function results in thick secretions in the lungs, intestines, pancreas, and bile ducts. In the pancreas, there is destruction of pancreatic function, oftenbefore birth. Some mutations result in less severe defects in CFTR function and later onset of lung disease and pancreatic insufficiency. Less common causes of pancreatic insufficiency are Shwachman-Diamond syndrome and Pearsonsyndrome in developed countries and severe malnutrition indeveloping countries. Available @ StudentConsult.com Failure to Thrive


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Pediatrics_Nelson. Available @ StudentConsult.com Failure to Thrive Children with pancreatic exocrine insufficiency havemany bulky, foul-smelling stools each day, usually withvisible oil or fat. They typically have voracious appetitesbecause of massive malabsorption of calories from fat,complex carbohydrates, and proteins. Failure to thrive isuniformly present if diagnosis and treatment are not accomplished rapidly. It is important to distinguish children withmalabsorption due to pancreatic disease from children withintestinal disorders that interfere with digestion or absorption. Appropriate testing should be performed to rule outconditions such as celiac disease and inflammatory boweldisease if any doubt about the state of pancreatic sufficiencyexists.


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Pediatrics_Nelson. Testing of pancreatic function is difficult. Direct measurement of enzyme concentrations in aspirated pancreatic juice is not routine and is technically difficult. Stools can be tested for the presence of maldigested fat, which usually indicates poor fat digestion. Measuring fecal fat can give either a qualitative assessment of fat absorption (fecal Sudan stain) or a semiquantitative measurement (72-hour fecal fat determination) of fat maldigestion. Another way to assess pancreatic function is to test for the presence of pancreatic enzymes in the stool. Of these, measuring fecal elastase-1 by immunoassay seems to be the most accurate method of assessment. Depressed fecal elastase-1 concentration correlates well with the presence of pancreatic insufficiency.


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Pediatrics_Nelson. Replacement of missing pancreatic enzymes is the best available therapy. Pancreatic enzymes are available as capsules containing enteric-coated microspheres. The coating on these spheres is designed to protect the enzymes from gastric acid degradation. For children unable to swallow capsules, the contents may be sprinkled on a spoonful of soft food, such as applesauce. Excessive use of enzymes must be avoided because high doses (usually >6000 U/kg/meal) can cause colonic fibrosis. In infants, typical dosing is 2000 to 4000 U of lipase/120 mL of formula. In children younger than 4 years old, 1000 U/kg/meal is given. For older children, 500 U/kg/meal is usual. This dose may be adjusted upward as required to control steatorrhea, but a dose of 2500 U/kg/meal should not be exceeded. Use of H2 receptor antagonists or proton-pump inhibitors can increase the efficacy of pancreatic enzymes by enhancing their release from the microspheres and reducing inactivation by acid.


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Pediatrics_Nelson. The exocrine pancreas produces numerous proteolyticenzymes, including trypsin, chymotrypsin, and carboxypeptidase. These are produced as inactive proenzymes to protectthe pancreas from autodigestion. Trypsin is activated after leaving the pancreas by enterokinase, an intestinal brush border enzyme. After activation, trypsin cleaves other proteolytic proenzymes into their active states. Protease inhibitorsfound in pancreatic juice inhibit early activation of trypsin;the presence of self-digestion sites on the trypsin moleculeallows for feedback inactivation. Pancreatitis occurs when digestive enzymes are activated inside the pancreas, causinginjury. Triggers for acute pancreatitis differ between adultsand children. In the adult patient, most episodes are relatedto alcohol abuse or gallstones. In children, most cases areidiopathic or due to medications. Some cases are caused bypancreatic sufficient cystic fibrosis, hypertriglyceridemia,biliary microlithiasis, trauma, or viral infection.


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Pediatrics_Nelson. In children, most cases areidiopathic or due to medications. Some cases are caused bypancreatic sufficient cystic fibrosis, hypertriglyceridemia,biliary microlithiasis, trauma, or viral infection. Collagenvascular disorders and parasite infestations are responsiblefor the remainder (Table 131-1).


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Pediatrics_Nelson. Available @ StudentConsult.com Acute pancreatitis presents with relatively rapid onset of pain, usually in the epigastric region. The pain may radiate to the back and is nearly always aggravated by eating. The patient moves frequently to find a position of comfort. Nausea and vomiting occur in most cases. Pain is typically continuous and quite severe, usually requiring narcotics. Severe pancreatitis can lead to hemorrhage, visible as ecchymoses in the flanks (Grey Turner sign) or periumbilical region (Cullen sign). Rupture of a minor pancreatic duct can lead to development of a pancreatic pseudocyst, characterized by persistent severe pain and tenderness and a palpable mass. With necrosis and fluid collections, patients experiencing severe pancreatitis are prone to infectious complications, and the clinician must be alert for fever and signs of sepsis.


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Pediatrics_Nelson. Acute pancreatitis can be difficult to diagnose. Elevations in total serum amylase or lipase support the diagnosis. These pancreatic enzymes are released into the blood during pancreatic injury. Nonspecific elevations of the enzymes are common, however. As acute pancreatitis progresses, the amylase level tends to decline faster than lipase, making the latter a Cholelithiasis and biliary sludge Choledochal cyst Pancreas divisum Anomalous junction of biliary and pancreatic ducts Annular pancreas Ampullary obstruction (mass, inflammation from Crohn’s disease) Ascaris infection good choice for diagnostic testing late in the course of the disease.


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Pediatrics_Nelson. Serial measurement of laboratory studies is importantto monitor for severe complications. At diagnosis, baseline complete blood count, C-reactive protein, electrolytes,blood urea nitrogen, creatinine, glucose, calcium, and phosphorus should be obtained. These should be measured atleast daily, along with amylase and lipase, until the patienthas recovered.


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Pediatrics_Nelson. Because enzyme levels are not 100% sensitive or specific,imaging studies are important for the diagnosis of pancreatitis. In acute pancreatitis, edema is present in all but themildest cases. Ultrasound is capable of detecting this edemaand should be performed as part of the overall diagnosticapproach. If overlying bowel gas obscures the pancreas, acomputed tomography (CT) scan allows complete visualization of the gland. CT scans should be done with oral andintravenous (IV) contrast agents to facilitate interpretation.Ultrasound and CT also can be used to monitor for the development of pseudocysts and for evidence of ductal dilation secondary to obstruction. The other important reason toperform imaging studies early in the course of pancreatitis isto rule out gallstones; the liver, gallbladder, and common bileduct all should be visualized. Magnetic resonance cholangiopancreatography may be used to detect anatomic variantscausing pancreatitis.


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Pediatrics_Nelson. There are no proven specific therapies for acute pancreatitis. If a predisposing etiology is found, such as a drug reaction or a gallstone obstructing the sphincter of Oddi, this should be specifically treated. Initially, oral intake is prohibited, an acid-blocking drug is prescribed, and (except in mild cases) nasogastric suction is begun. Fluid resuscitation is necessary because of vomiting and third space losses. Pain relief should be provided. Meperidine, fentanyl, and hydromorphone are most commonly used. Nutritional support should be provided early in the course if the patient will be nothing by mouth (NPO) for extended periods. Feedings can begin once pain subsides or can be administered downstream from the duodenum. If this is not possible, parenteral nutrition is an option. Fewer complications and more rapid recovery occur with jejunal feedings compared with parenteral nutrition. Antibiotics should be considered if the patient is febrile, has extensive pancreatic necrosis, or


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Pediatrics_Nelson. complications and more rapid recovery occur with jejunal feedings compared with parenteral nutrition. Antibiotics should be considered if the patient is febrile, has extensive pancreatic necrosis, or has laboratory evidence of infection. A broad-spectrum antibiotic, such as imipenem, is considered the best choice.


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Pediatrics_Nelson. Chronic pancreatitis is defined as recurrent or persistentattacks of pancreatitis, which have resulted in irreversible morphologic changes in pancreatic structure. Theseinclude scarring of the ducts with irregular areas of narrowing and dilation (beading), fibrosis of parenchyma, andloss of acinar and islet tissue. Pancreatic exocrine insufficiency and diabetes mellitus may result from unremittingchronic pancreatitis. Most patients have discrete attacksof acute symptoms occurring repeatedly, but chronic painmay be present. The causes of chronic pancreatitis include hereditary pancreatitis and milder phenotypes of cysticfibrosis associated with pancreatic sufficiency. Familial disease is caused by one of several known mutations in thetrypsinogen gene. These mutations obliterate autodigestionsites on the trypsin molecule, inhibiting feedback inhibition of trypsin digestion. Genetic testing is readily available for these mutations. Genetic testing for cystic fibrosiscan be performed, but


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Pediatrics_Nelson. on the trypsin molecule, inhibiting feedback inhibition of trypsin digestion. Genetic testing is readily available for these mutations. Genetic testing for cystic fibrosiscan be performed, but must include screening for the lesscommon mutations associated with pancreatic sufficiency.Sweat chloride testing is less expensive and is abnormalin most. Less commonly, mutations in the SPINK1 gene, which codes for pancreatic trypsin inhibitor, and PRSS1, amutation of cationic trypsinogen, are found.


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Pediatrics_Nelson. Children with chronic pancreatitis initially present withrecurring attacks of acute pancreatitis. Injury to the pancreatic ducts predisposes these children to continued attacksowing to scarring of small and large pancreatic ducts, stasisof pancreatic secretions, stone formation, and inflammation. Loss of pancreatic exocrine and endocrine tissue overtime can lead to exocrine and endocrine deficiency. Morethan 90% of the pancreatic mass must be destroyed beforeexocrine deficiency becomes clinically apparent; this is alate complication that does not occur in all cases. Chronicpain is a serious problem in most affected individuals.These patients have many episodes; many do not requirehospitalization.


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Pediatrics_Nelson. Laboratory diagnosis of chronic pancreatitis is similar to acute pancreatitis but with more severe loss of pancreatic tissue it becomes less likely that the patient with elevation of amylase or lipase. Monitoring also should include looking for consequences of chronic injury, including diabetes mellitus and compromise of the pancreatic and biliary ducts. Pancreatic and biliary imaging has been accomplished by endoscopic retrograde cholangiopancreatography (ERCP). ERCP offers the possibility of therapeutic intervention to remove gallstones, dilate strictures, and place stents to enhance flow of pancreatic juice. Magnetic resonance cholangiopancreatography is an alternative to ERCP. Plain abdominal x-rays may show pancreatic calcifications. Diagnostic testing for the etiology of chronic pancreatitis should include genetic testing for hereditary pancreatitis and cystic fibrosis and sweat chloride determination.


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Pediatrics_Nelson. Treatment is largely supportive. Potential but unproven therapies include the use of daily pancreatic enzyme supplements, octreotide (somatostatin) to abort early attacks, low-fat diets, and daily antioxidant therapy. Care must be taken that extreme diets do not result in nutritional deprivation. Interventional ERCP to dilate large strictures and remove stones and surgical pancreatic drainage procedures to decompress dilated pancreatic ducts by creating a side-to-side pancreaticojejunostomy may have some value.


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Pediatrics_Nelson. The peritoneum consists of a single layer of mesothelial cells that covers all intra-abdominal organs. The portion that covers the abdominal wall is derived from the underlying somatic structures and is innervated by somatic nerves. The portion covering the viscera is derived from visceral mesoderm and is innervated by nonmyelinated visceral afferents. Inflammation of the peritoneum, or peritonitis, usually is caused by infection but may result from exogenous irritants introduced by penetrating injuries or surgical procedures, radiation, and endogenous irritants such as meconium. Infectious peritonitis can be an acute complication of intestinal inflammation and perforation, as in appendicitis, or it can occur secondary to contamination of preexisting ascites associated with renal, cardiac, or hepatic disease. In this setting, when there is no other intra-abdominal source, it is referred to as spontaneous bacterial peritonitis. Spontaneous bacterial peritonitis is usually due to


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Pediatrics_Nelson. or hepatic disease. In this setting, when there is no other intra-abdominal source, it is referred to as spontaneous bacterial peritonitis. Spontaneous bacterial peritonitis is usually due to pneumococcus and less often to Escherichia coli.


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Pediatrics_Nelson. Available @ StudentConsult.com Peritonitis is characterized on examination by marked abdominal tenderness. Rebound tenderness also generally is quite pronounced. The patient tends to move very little owing to intense peritoneal irritation and pain. Fever is not always present, and absence of fever should not be regarded as contradictory to the diagnosis. Patients who are taking corticosteroids for an underlying condition, such as nephrotic syndrome, are likely to have little fever and reduced tenderness.


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Pediatrics_Nelson. Blood tests should focus on identifying the nature of the inflammation and its underlying cause. An elevated white blood cell count, erythrocyte sedimentation rate, and C-reactive proteinsuggest infection. In children older than 5 years, appendicitis isthe leading cause. Total serum protein, albumin, and urinalysisshould be ordered to rule out nephrotic syndrome. Liver function tests should be performed to rule out chronic liver diseasecausing ascites. The best way to diagnose suspected peritonitisis to sample the peritoneal fluid with a needle or catheter (paracentesis). Peritoneal fluid in spontaneous bacterial peritonitis has a high neutrophil count of greater than 250 cells/mm3. Other tests that should be run on the peritoneal fluid includeamylase (to rule out pancreatic ascites), culture, albumin, andlactate dehydrogenase concentration. For culture, a large sampleof fluid should be placed into aerobic and anaerobic blood culture bottles immediately on obtaining the sample.


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Pediatrics_Nelson. Appendicitis may be identified by ultrasound or computed tomography (CT) scan. When other intra-abdominal emergencies are suspected, such as midgut volvulus, meconium ileus, peptic disease, or any other condition predisposing to intestinal perforation, specific testing should be performed. Peritonitis caused by an intra-abdominal surgical process, such as appendicitis or a penetrating wound, must be managed surgically. Spontaneous bacterial peritonitis should be treated with a broad-spectrum antibiotic with good coverage of resistant pneumococcus and enteric bacteria. Cefotaxime is generally effective as initial therapy while awaiting culture and sensitivity results. Anaerobic coverage with metronidazole should be added whenever a perforated viscus is suspected. Bishop W, editor: Pediatric Practice: Gastroenterology, New York, 2010, Feldman M, Friedman LS, Brandt LJ, editors: Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/Management, Philadelphia, 2010,


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Pediatrics_Nelson. Feldman M, Friedman LS, Brandt LJ, editors: Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/Management, Philadelphia, 2010, Kleinman R, Goulet OJ, Mieli-Vergani G, et al: Walker’s Pediatric Gastrointestinal Disease, Hamilton, Ontario, 2008, BC Decker Kliegman RM, Stanton BF, St. Jeme JW, et al: Nelson Textbook of Pediatrics, ed 19, Philadelphia, 2011, Saunders Wyllie R, Hyams JS, Kay M, editors: Pediatric Gastrointestinal and Liver Disease, Philadelphia, 2011, Saunders The Respiratory System Thida Ong, Amanda Striegl, and Susan G. Marshall 18


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Pediatrics_Nelson. Wyllie R, Hyams JS, Kay M, editors: Pediatric Gastrointestinal and Liver Disease, Philadelphia, 2011, Saunders The Respiratory System Thida Ong, Amanda Striegl, and Susan G. Marshall 18 Acute and chronic respiratory diseases are common in pediatrics. Children with respiratory problems typically present with symptoms, although abnormal imaging may sometimes precede physical findings. The underlying etiology of childhood respiratory diseases includes the following: genetic (e.g., cystic fibrosis); anatomic (e.g., laryngomalacia); incomplete maturation (e.g., premature birth); iatrogenic (e.g., oxygen toxicity); immunologic (e.g., immune deficiency); infectious (e.g., croup or pneumonia); environmental (e.g., toxins or pollutants); and extrapulmonary (e.g., congenital heart disease). The optimal functioning of the entire respiratory tract allows children not only to survive, but thrive.


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Pediatrics_Nelson. Air enters the nose and passes over the large surface area of the nasal turbinates, which warm, humidify, and filter the inspired air. Secretions draining from the paranasal sinuses are carried to the pharynx by the mucociliary action of the ciliated respiratory epithelium. Lymphoid tissue can obstruct airflow through the nasopharynx (adenoids) or the posterior pharynx (tonsils).


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Pediatrics_Nelson. The epiglottis protects the larynx during swallowing by deflecting material toward the esophagus. The arytenoid cartilages, which assist in opening and closing the glottis, are less prominent in children than in adults. The opening formed by the vocal cords (the glottis) is V-shaped, with the apex of the V being anterior. Below the vocal cords, the walls of the subglottic space converge toward the cricoid portion of the trachea. In children under 3 years of age, the cricoid ring is the narrowest portion of the airway, whereas in older children and adults it is the glottis. C-shaped cartilage, extending approximately 320° around the airway circumference, supports the trachea and mainstem bronchi. The posterior wall of the trachea is membranous. Beyond the lobar bronchi, the cartilaginous support for the airways becomes discontinuous.


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Pediatrics_Nelson. The right lung has three lobes (upper, middle, lower) andcomprises approximately 55% of the total lung volume. The leftlung has two lobes (upper, lower). The inferior division of theleft upper lobe, the lingula, is analogous to the right middle lobe. The pediatric lung has tremendous capacity for growth. A full-term infant has approximately 25 million alveoli; an adult nearly 300 million alveoli. The growth of new alveoli occurs during the first 2 years of life and is complete by 8 years of age. After this time, lung volume increases primarily by increase in alveolar dimensions, with new alveoli rarely formed. The major function of the lungs is to exchange oxygen (O2)and carbon dioxide (CO2) between the atmosphere and the blood. The anatomy of the airways, mechanics of the respiratory muscles and rib cage, nature of the alveolar-capillary interface, pulmonary circulation, tissue metabolism, and neuromuscular control of ventilation all influence gas exchange.


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Pediatrics_Nelson. Air enters the lungs when intrathoracic pressure is less than atmospheric pressure. During inspiration, negative intrathoracic pressure is generated by contraction and lowering of the diaphragm. The accessory muscles of inspiration (external intercostal, scalene, and sternocleidomastoid muscles)are not used during quiet breathing but are recruited during exercise or in disease states to raise and enlarge the rib cage. Exhalation is normally passive, but with active exhalation, the abdominal and internal intercostal muscles are recruited. During normal breathing at rest, lung volumes are usually inthe mid-range of inflation (Fig. 133-1). Tidal volume (TV) is the amount of air inspired with each relaxed breath. The volume of gas retained in the lung at the end of a relaxed exhalation is


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Pediatrics_Nelson. Figure 133-1 Lung volumes and capacities. Vital capacity and its subdivisions can be measured by spirometry, but calculation of residual volume requires measurement of functional residual capacity by body plethysmography, helium dilution, or nitrogen washout. (From Andreoli TE, Bennett JC, Carpenter CJ, et al, editors: Cecil Essentials of Medicine, ed 4, Philadelphia, 1997, WB Saunders, p 127.) Ventilation-perfusion Asthma ↓ Normal, ↓, or ↑ Yes FIO2, Fraction of inspired oxygen; PaCO2, arterial partial pressure of carbon dioxide; PaO2, arterial partial pressure of oxygen.


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Pediatrics_Nelson. Ventilation-perfusion Asthma ↓ Normal, ↓, or ↑ Yes FIO2, Fraction of inspired oxygen; PaCO2, arterial partial pressure of carbon dioxide; PaO2, arterial partial pressure of oxygen. the functional residual capacity (FRC). This gas volume maintains exchange of O2 during exhalation. Total lung capacity (TLC) is the volume of gas in the lungs at the end of maximal inhalation and residual volume (RV) is the volume of gas left in the lungs at the end of a maximal exhalation. Vital capacity (VC) is the maximal amount of air that can be expelled fromthe lungs and is the difference between TLC and RV.


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Pediatrics_Nelson. Airway resistance is influenced by the diameter and length of the conducting airways, the viscosity of gas, and the nature of the airflow. During quiet breathing, airflow in the smaller airways may be laminar (streamlined), and resistance is inversely proportional to the fourth power of the radius of the airway. At higher flow rates, turbulent flow, especially in the larger airways, increases resistance. Relatively small changes in airway diameter can result in large changes in airway resistance. Excessive airway secretions, bronchospasm, mucosal edema and inflammation, airway stenosis, foreign bodies, loss of airway wall integrity (as with bronchiectasis), and airway compression may all produce symptomatic increases in airway resistance. In pediatrics, laryngomalacia and croup are very common causes of increased upper airway resistance; whereas asthma, bronchiolitis and cystic fibrosis (CF) are among the most common causes of increased lower airway resistance.


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Pediatrics_Nelson. Lung compliance (change in volume for a given change in pressure) is a measure of the ease with which the lung can be inflated. Processes that decrease lung compliance (surfactant deficiency, pulmonary fibrosis, pulmonary edema) may lead to decreases in measured lung volumes. Restrictive lung diseases are characterized by normal to low FRC and RV, low TLC and VC, decreased lung compliance, and relatively normal flow rates. Restrictive lung disease can result from neuromuscular weakness, an alveolar filling process (lobar pneumonia, pulmonary edema), pleural disease (pleural effusion, inflammation, or mass), thoracic narrowing/stiffness (scoliosis, severe pectus excavatum), and abdominal distention. Alveolar ventilation is defined as the exchange of carbon dioxide between the alveoli and external environment.


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Pediatrics_Nelson. Alveolar ventilation is defined as the exchange of carbon dioxide between the alveoli and external environment. Normally, about 30% of each tidal breath fills the conducting (non–gas-exchanging) airways (anatomic dead space).Because the anatomic dead space is relatively constant, increasing the tidal volume may increase the efficacy of ventilation. Conversely, if tidal volume decreases, then the dead space/tidal volume ratio increases, and alveolar ventilation decreases.


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Pediatrics_Nelson. Gas exchange depends on alveolar ventilation, pulmonary capillary blood flow, and the diffusion of gases across the alveolar-capillary membrane. Exchange of CO2 is determined by alveolar ventilation, whereas the exchange of O2 is influenced primarily by the regional matching of ventilation (V) with pulmonary blood flow (Q) (V/Q matching). V/Q matching is maintained, in part, by hypoxic pulmonary vasoconstriction (local constriction of the pulmonary vessels in areas that are hypoventilated). There are five causes of hypoxemia (Table 133-1). Disorders resulting in V/Q mismatching (such as pneumonia and atelectasis) are the most common causes of hypoxemia. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com The lungs are constantly exposed to particles and infectious agents. The nose is the primary filter for large particles. The ciliated epithelium of the paranasal sinuses and nasal turbinates move filtered particles toward the pharynx. Particles less than 10 μm in diameter may reach the trachea and bronchi and deposit on the mucosa. Particles less than 1 μm may reach the alveoli. Ciliated cells lining the airways from the larynx to the bronchioles continuously propel a thin layer of mucus toward the mouth. Alveolar macrophages and polymorphonuclear cells engulf particles and pathogens that have been opsonized by locally secreted IgA antibodies or transudated serum antibodies.


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Pediatrics_Nelson. Cough, important in protecting the lungs, is a forcefulexpiration that can clear the airways of debris and secretions.Cough may be voluntary or generated by reflex irritation ofthe nose, sinus, pharynx, larynx, trachea, bronchi, or bronchioles. Effective cough requires the ability to (1) inhale to near total lung capacity, (2) close and open the glottis, and (3) contract abdominal muscles to forcibly exhale. Loss of theability to cough, as with neuromuscular weakness, results in poor secretion clearance and predisposes to atelectasis andpneumonia. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com The complete respiratory history includes onset, duration, and frequency of respiratory symptoms (cough, noisy breathing, work of breathing/exercise tolerance, nasal congestion, sputum production), swallowing function (especially in infants), and exposure to others with respiratory illness. It is important to obtain information concerning the severity (hospitalizations, emergency department visits, missed school days) and pattern (acute, chronic, or intermittent) of symptoms. For infants, a feeding history should be obtained, including questions of coughing or choking with feeds. Family history should include questions about asthma and atopy, immune deficiencies, and CF. The environmental historyqueries exposure to smoke, pets, and pollutants. Travel history may also be relevant. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com Clothing should be removed from the upper half of the child’s body so that the thorax may be inspected, although maintaining modesty for adolescents should be respected. It is optimal to observe the respiratory pattern, rate, and work of breathing while the child is quiet, noting the shape and symmetry of the chest wall and the anteroposterior (AP) diameter. Any factor that impairs respiratory mechanics is likely to increase the respiratory rate. However, nonrespiratory causes of tachypnea include fever, pain, and anxiety. Respiratory rates vary with age and activity (Table 133-2).


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Pediatrics_Nelson. It is important to observe the respiratory pattern and degree of effort (work of breathing). Hyperpnea (increased depth of respiration) may be observed with fever, metabolic acidosis, pulmonary and cardiac disease, or extreme anxiety. Hyperpnea without signs of respiratory distress suggests an extrapulmonary etiology (metabolic acidosis, fever, pain). Increased work of breathing can be described as inspiratory (intercostal, supraclavicular, or substernal retractions) or CNS, Central nervous system. expiratory (use of abdominal muscles to actively exhale). In children, increased inspiratory effort is also manifested by nasal flaring. Grunting (forced expiration against a partially closed glottis) suggests respiratory distress, but it may also be a manifestation of pain.


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Pediatrics_Nelson. Causes of increased work of breathing during inspiration include extrathoracic airway obstruction (laryngomalacia, croup, subglottic stenosis) and/or decreased pulmonary compliance (pneumonia, pulmonary edema). Increased expiratory work of breathing usually indicates intrathoracic airway obstruction (see Table 133-2).


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Pediatrics_Nelson. Stridor is a harsh sound caused by a partially obstructedextrathoracic airway, more commonly heard on inspiration.Wheezing is produced by partial obstruction of the lower airways, more commonly heard during exhalation. Wheezes canbe monophonic and low-pitched (usually from large, centralairways) or high-pitched and musical (from small peripheralairways). Secretions in the intrathoracic airways may producewheezing but more commonly result in irregular sounds calledrhonchi. Fluid or secretions in small airways may produce sounds characteristic of crumpling cellophane (crackles or rales). Having the child take a deep breath and exhale forcefullywill accentuate many abnormal lung sounds. Decreased breathsounds may be due to atelectasis, lobar consolidation (pneumonia), thoracic mass, or a pleural effusion. Observation of respiratory rate, work of breathing, tracheal and cardiac deviation,and chest wall motion, combined with percussion and auscultation, helps to identify intrathoracic


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Pediatrics_Nelson. pleural effusion. Observation of respiratory rate, work of breathing, tracheal and cardiac deviation,and chest wall motion, combined with percussion and auscultation, helps to identify intrathoracic disease (Table 133-3).


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Pediatrics_Nelson. Digital clubbing is seen in CF and in other, less common chronic pulmonary diseases (such as interstitial lung disease). It is generally not seen in asthma, so its presence should heighten concern for other diagnoses. Clubbing may also be present in nonpulmonary chronic diseases (cardiac, gastrointestinal, or hematologic) or, rarely, as a familial trait. Pleural effusion Deviation to Reduced over None or Dull None Egophony Muffled opposite side area reduced Interstitial No Reduced Normal to Normal Normal Inspiratory None process Adapted from Andreoli TE, Bennett JC, Carpenter CJ, et al, editors: Cecil Essentials of Medicine, ed 4, Philadelphia, 1997, WB Saunders, p 115. PMI, Point of maximum impulse. *In egophony, e sounds like a (may be a sign of consolidation but also is associated with moderate-sized pleural effusions). †In pectoriloquy, words/voice sounds clearer over the affected site (associated with consolidation and cavitary lesions).


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Pediatrics_Nelson. Cough results from stimulation of irritant receptors in the airway mucosa. Acute cough generally is associated with respiratory infections or irritant exposure (smoke) and subsides as the infection resolves or the exposure is eliminated. The characteristics of the cough and the circumstances under which the cough occurs help in determining the cause. Sudden onset after a choking episode suggests foreign body aspiration. Morning cough may be due to the accumulation of excessive secretions during the night from sinusitis, allergic rhinitis, or bronchial infection. Nighttime coughing is a hallmark of asthma and can also be caused by gastroesophageal reflux disease. Cough exacerbated by lying flat may be due to postnasal drip, sinusitis, allergic rhinitis, or reflux. Recurrent coughing with exercise is suggestive of exercise-induced asthma/bronchospasm. Paroxysmal cough suggests pertussis or foreign body aspiration. A repetitive, staccato cough occurs in chlamydial infections in infants.


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Pediatrics_Nelson. is suggestive of exercise-induced asthma/bronchospasm. Paroxysmal cough suggests pertussis or foreign body aspiration. A repetitive, staccato cough occurs in chlamydial infections in infants. A harsh, brassy, seal-like cough suggests croup, tracheomalacia, or psychogenic (habit) cough. The last, which is most common in teenagers, disappears during sleep. Younger children can develop a throat-clearing habit cough, which also disappears during sleep.


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Pediatrics_Nelson. Chronic cough is defined as a daily cough lasting longer than 3 weeks. Common causes of chronic cough are asthma, postnasal drip (allergic rhinitis, sinusitis), and postinfectious tussive syndromes. It can also be caused by gastroesophageal reflux disease, swallowing dysfunction (infants), anatomic abnormalities (tracheoesophageal fistula, tracheomalacia), and chronic infection. Persistent cough may also be caused by exposure to irritants (tobacco and wood stove smoke) or foreign body aspiration, or it may be psychogenic in origin. During the first several years of life, children experience frequent viral respiratory infections, especially if they have multiple older siblings or attend day care or preschool. Cough that resolves promptly and is clearly associated with a viral infection does not require further diagnostic workup. However, cough persisting longer than 3 weeks warrants further evaluation.


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Pediatrics_Nelson. Chest radiographs are useful in assessing respiratory disease in children. In addition to determining lung abnormalities, they provide information about the bony thorax (rib or vertebral abnormalities), the heart (cardiomegaly, pericardial effusion), and the great vessels (right aortic arch/vascular rings, rib notching). Chest radiographs should be obtained in both the posteroanterior (PA) and lateral projections and, if possible, following a full inspiration. Estimation of lung hyperinflation based on a single PA view is unreliable; flattened diaphragms and an increased AP diameter on lateral projection is a better indicator of hyperinflation. Crowding of the blood vessels with poor inspiration can be misinterpreted as increased markings or infiltrates. External skin folds, rotation, and motion may produce distorted or unclear images. Expiratory views and fluoroscopy may detect partial bronchial obstruction due to an aspirated foreign body that results in regional hyperinflation,


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Pediatrics_Nelson. and motion may produce distorted or unclear images. Expiratory views and fluoroscopy may detect partial bronchial obstruction due to an aspirated foreign body that results in regional hyperinflation, because the affected lung or lobe does not deflate on exhalation. Fluoroscopy can also be used to evaluate diaphragm movement.


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Pediatrics_Nelson. A barium esophagram may be valuable in diagnosing disorders of swallowing (dysphagia) and esophageal motility, vascular rings (esophageal compression), tracheoesophageal fistulas, and, to a lesser extent, gastroesophageal reflux. When evaluating for a tracheoesophageal fistula, contrast material must be instilled under pressure via a catheter with the distal tip situated in the esophagus (see Chapter 128). A computed tomography (CT) scan of the chest is the imaging test of choice for evaluating pleural masses, bronchiectasis, and mediastinal lesions as well as delineating pleural from parenchymal lesions. CT scans with intravenous contrast provide excellent information about the pulmonary vasculature and great vessels and can detect pulmonary embolism. High-resolution CT scans are used to assess lung parenchyma (congenital pulmonary malformations, interstitial lung disease) and the airways (bronchiectasis). The speed of current


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Pediatrics_Nelson. CT scanners makes it possible to scan most children without sedating them. However, sedation may be required in infants and toddlers to decrease motion artifact. Magnetic resonance imaging (MRI), useful in visualizing cardiac and great vessel anatomy, is less useful for evaluation of pulmonary parenchymal lesions. Ultrasonography can be used to delineate some intra-thoracic masses and is the imaging procedure of choice for assessing parapneumonic effusion/empyema. It is useful for assessing diaphragmatic motion in small children. Measures of Respiratory Gas Exchange


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Pediatrics_Nelson. Measures of Respiratory Gas Exchange A properly performed arterial blood gas analysis provides information about the effectiveness of both oxygenation and ventilation. However, arterial samples are more difficult to obtain, so capillary and venous blood samples are more commonly used. The Pco2 from a capillary sample is similar to that from arterial blood. The Pco2 in venous samples is approximately 6 mm Hg higher than arterial Pco2. The ratio of the serum bicarbonate concentration to Pco2 determines the pH. Capillary or venous samples should not be used to assess oxygenation.


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Pediatrics_Nelson. There are both respiratory and metabolic causes of acidosis (see Chapter 37). In the presence of an alkalosis or acidosis, respiratory compensation (altering Pco2 to maintain a normal pH) can occur within minutes, but renal compensation (altering the serum bicarbonate level) may not be complete for several days. Recall that both the respiratory and metabolic compensation are incomplete, so pH will remain on the side of the primary insult (whether acidosis or alkalosis).


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Pediatrics_Nelson. Pulse oximetry measures the O2 saturation of hemoglobin by measuring the blood absorption of two or more wavelengths of light. It is noninvasive, easy to use, and reliable. Because of the shape of the oxyhemoglobin dissociation curve, O2 saturation does not decrease much until the Po2 reaches approximately 60 mm Hg. Pulse oximetry may not accurately reflect true O2 saturation when abnormal hemoglobin is present (carboxyhemoglobin, methemoglobin), when perfusion is poor, or if no light passes through to the photodetector (nail polish).


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Pediatrics_Nelson. The measurement of Pco2 is accomplished most reliably by blood gas analysis. However, there are noninvasive monitors that record exhaled Pco2 (end-tidal CO2), which is representative of alveolar Pco2. End-tidal Pco2 measurements are most commonly used in intubated and mechanically ventilated patients, but some devices can measure Pco2 at the nares. Transcutaneous electrodes can be used to monitor Pco2 and Po2 at the skin surface, but are less accurate. Noninvasive techniques of CO2 measurement are best suited for detecting trends rather than for providing absolute values.


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Pediatrics_Nelson. Measurement of lung volumes and airflow rates using spirometry are important in assessing pulmonary disease. The patient inhales to TLC and then forcibly exhales until no more air can be expelled. During the forced expiratory maneuver, forced vital capacity (FVC), forced expired volume in the first second (FEV1), and forced expiratory flow (FEF) rates are measured. These are compared to predicted values based on patient age, gender, and race, but rely mostly on height. Most children above 6 years of age can perform spirometry. Infant pulmonary function testing is possible, using sedation and sophisticated equipment. Airway resistance, FRC, and RV cannot be measured with spirometry and require other techniques, such as body plethysmography. Helium dilution can also measure TLC and RV by determining the magnitude of dilution of inhaled helium in the air within the lung, but may underestimate air trapping.


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Pediatrics_Nelson. Abnormal results on pulmonary function testing can beused to categorize obstructive airway disease (low flow rates and increased RV or FRC) or a restrictive defect (low FVCand TLC, with relative preservation of flow rates and FRC).When the FEV1 and flow rates are decreased to a greaterextent than the FVC, then airway obstruction is likely; however, a proportional decrease in FVC, FEV1, and flow rates suggests a restrictive lung defect. The mean midexpiratoryflow rate (FEF25–75%) is a more sensitive measure of small airways disease than the FEV1, but is also more variable. Pulmonary function testing can detect reversible airway obstruction characteristic of asthma with a significant improvementin FEV1 (>12%-15%) or in FEF25–75% (>25%) followinginhalation of a bronchodilator. Spirometry is also useful forlongitudinal patient management. The peak expiratory flow rate (PEFR) can be obtained with a simple handheld deviceand may be useful for home monitoring of older childrenwith asthma.


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Pediatrics_Nelson. also useful forlongitudinal patient management. The peak expiratory flow rate (PEFR) can be obtained with a simple handheld deviceand may be useful for home monitoring of older childrenwith asthma. However, it is highly dependent on patienteffort, and values must be interpreted with caution. Inhalation challenge tests using methacholine, histamine, or cold, dry air are used to assess airway hyperreactivity, but require sophisticated equipment and special expertise and should be performed only in a pulmonary function laboratory with experienced technicians.


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Endoscopic Evaluation of the Airways

Pediatrics_Nelson. Endoscopic Evaluation of the Airways


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Pediatrics_Nelson. Endoscopic evaluation of the upper airways (nasopharyngoscopy) is performed with a flexible fiberoptic nasopharyngoscope to assess adenoid size, patency of the nasal passages, and abnormalities of the glottis. It is especially useful in evaluating stridor and assessing vocal cord motion/function, and it does not require sedation. Endoscopic evaluation of the subglottic space and intrathoracic airways can be done with either a flexible or rigid bronchoscope under anesthesia. Bronchoscopy is useful in identifying airway abnormalities (stenosis, malacia, endobronchial lesions, excessive secretions) and in obtaining airway samples for culture (bronchoalveolar lavage), especially in immunocompromised patients. Rigid bronchoscopy is the method of choice for removing foreign bodies from the airways and performing other interventions, and flexible bronchoscopy is most useful as a diagnostic tool and for obtaining lower airway cultures. Transbronchial biopsies are rarely performed in children.


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Pediatrics_Nelson. and performing other interventions, and flexible bronchoscopy is most useful as a diagnostic tool and for obtaining lower airway cultures. Transbronchial biopsies are rarely performed in children. There are few absolute contraindications to bronchoscopy. Relative contraindications include bleeding diatheses, thrombocytopenia (<50,000/cm3), and clinical conditions when the patient is too unstable to tolerate the procedure.


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Pediatrics_Nelson. Examination of Sputum Sputum specimens may be useful in evaluating lower respiratory tract infections, but they are difficult to obtain in young children. In addition, an expectorated specimen may not provide a representative sample of lower airway secretions. Specimens containing large numbers of squamous epithelial cells either are not from the lower airways or are heavily contaminated with upper airway secretions and may yield misleading results. Sputum in patients with lower respiratory tract bacterial infections often contains polymorphonucleated leukocytes and one predominant organism on culture. If sputum cannot be obtained, then bronchoalveolar lavage specimens may be used for microbiologic diagnosis in selected situations. In patients with CF who cannot produce sputum, specially processed throat cultures are often used as surrogates for lower airway cultures.


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Pediatrics_Nelson. When less invasive methods fail to provide diagnoses in patients with pulmonary disease, a lung biopsy may be required. Concern for childhood interstitial lung disease, atypical infection (especially in an immunocompromised host), and evaluation of a mass/malformation are the most common indications for biopsy. CT-guided needle biopsy performed by an interventional radiologist is an option if limited histology is needed and the lesion is amenable to percutaneous approach (e.g., fungal nodules). Either a thoracoscopic procedure or a thoracotomy is preferred if thorough histologic evaluation is desired. Thoracotomy allows the surgeon to inspect and palpate the lung, which aids in choosing the best site for biopsy, but it is more invasive than thoracoscopy. In most cases, infants and children tolerate lung biopsy well.


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Pediatrics_Nelson. Any child in respiratory distress should be treated with supplemental O2 to maintain normal O2 saturation levels. For long-term administration of O2, a nasal cannula is the most widely used device, as it enables patients to eat and speak unhindered by the O2 delivery system. Though nasal cannula is the easiest way to provide supplemental O2, the actual fraction of inspired oxygen (FIO2) delivered to the patient can be quite variable and affected by the child’s size and respiratory pattern. Humidified high flow nasal cannula (HFNC) allows the provider to more comfortably deliver higher flow rates while controlling the FIO2 and is now widely used in neonates as an alternative to noninvasive positive pressure. Supplemental O2 may also be delivered by a variety of face-mask systems ranging from a simple face mask, which can provide 30% to 40% O2, to a nonrebreather mask with reservoir that can provide nearly 100% O2.


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Pediatrics_Nelson. The concentration of administered O2 should be high enough to relieve hypoxemia. The acceptable O2 saturation depends on the patient and clinical situation. Generally, supplemental O2 should be administered to achieve a goal saturation level above 90%. Normal oxygen saturation is greater than 95%. It is unnecessary to achieve 100% saturation, especially if this requires potentially toxic levels of inspired O2 for extended periods of time. Inspired O2 concentrations less than 40% are usually safe for long-term use. Patients requiring supplemental O2 should be monitored with pulse oximetry, either intermittently or continuously, or with arterial blood gas measurements of Po2 to allow titration to the lowest possible O2 concentration.


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Pediatrics_Nelson. Delivering therapeutic agents to the lower respiratory tract can be accomplished by inhalation of aerosol forms of the agents via dry powder inhaler (DPI), metered dose inhaler (MDI), or nebulizer. All of these devices are designed to generate relatively small particles that can bypass the filtering action of the upper airway and deposit in the lower airways. Many factors influence drug deposition, including patient technique, device used, age of the child, and breathing pattern. Nebulizers should be used with a face mask (infants) or mouthpiece (children and teens) to minimize loss of drug to ambient air. Plastic holding chambers (spacers) are available for all ages and should always be used with MDIs. Dry powder inhalers require a single rapid deep inhalation for optimal drug delivery, which is difficult for children under 6 years of age. MDIs and nebulizers are equally effective in delivering medications only if the technique is correct, so it is important to review this frequently


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Pediatrics_Nelson. is difficult for children under 6 years of age. MDIs and nebulizers are equally effective in delivering medications only if the technique is correct, so it is important to review this frequently and carefully with families.


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Pediatrics_Nelson. When disease processes impair clearance of pulmonary secretions, airway clearance techniques may help maintain airway patency. One method is chest percussion, which moves secretions toward the central airways, from which they can be expectorated. Chest physiotherapy can also be performed effectively with handheld devices that generate expiratory back-pressure and vibration (TheraPEP, Flutter, and Acapella) and pneumatic vests. Chest physiotherapy is most beneficial in children with chronic airway secretions, especially those with CF. Children who are too weak to generate an effective cough benefit from the use of a mechanical cough assist device, used in conjunction with chest physiotherapy. Chest physiotherapy is not generally beneficial for patients with asthma or pneumonia, and its effectiveness in patients with atelectasis has not been clearly established.


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Pediatrics_Nelson. If the upper airway is obstructed or mechanical ventilation is needed, it may be necessary to provide the patient with an artificial airway. This is best done by placing an endotracheal tube via the mouth or nose into the trachea (intubation).Intubation alters the physiology of the respiratory tract in many ways, not all of which are beneficial. It interferes with the humidification, warming, and filtration of inspired air and prevents phonation. Intubation also stimulates secretion production. However, in acute/impending respiratory failure, intubation with an endotracheal tube is lifesaving.


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Pediatrics_Nelson. Endotracheal tubes can damage the larynx and the airways if the tubes are of improper size and are not carefully maintained. The cricoid ring is the narrowest segment of a child’s airway and is completely surrounded by cartilage, which makes it vulnerable to damage, and may lead to subglottic stenosis. If the pressure created by the tube against the airway mucosa exceeds capillary filling pressure (roughly 35 cm H2O), mucosal ischemia develops, leading to necrosis. Therefore, a small air leak should be maintained around the endotracheal tube to minimize the risk of mucosal damage.


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Pediatrics_Nelson. Artificial airways must be kept clear of secretions asobstruction with mucous plugs can be fatal. Providing adequate humidification of inspired air and appropriate suctioning of the tube reduce the probability of occlusion by secretions. In addition to endotracheal tubes, the laryngeal mask airway (LMA) can be used to provide mechanical ventilation. This device consists of a tube with a soft mask at the distal end that is placed over the larynx, creating a seal without the trachea being instrumented. Although less invasive,the LMA is less secure, so it is generally limited to proceduralanesthesia.


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Pediatrics_Nelson. Tracheostomy is the surgical placement of an artificial airway into the trachea below the larynx. If prolonged intubation is anticipated, elective tracheostomy may be used to prevent laryngeal trauma, obviate the danger of accidental extubation, increase patient comfort, and facilitate nursing care. No clear guidelines are available as to how long patients can be intubated without sustaining airway damage or when a tracheostomy is indicated.


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Pediatrics_Nelson. Children with severe chronic upper airway obstruction or those requiring long-term mechanical ventilation may benefit from tracheostomies. Because the tracheostomy tube hampers the ability to phonate and communicate, the child must be monitored carefully at all times. As with endotracheal tubes, tracheostomy tubes must be kept clear of secretions. Occlusion of the tube or accidental dislodgment of the tube can be fatal. Many children with tracheostomy tubes can be cared for at home provided the caregivers are well trained and adequately equipped. Patients who are unable to maintain adequate gas exchange may require mechanical ventilation. Most modes of mechanical ventilation involve inflation of the lungs with gas using positive pressure. The inspiratory phase is active (air is pushed in) and exhalation is passive.


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Pediatrics_Nelson. Positive-pressure ventilation often requires an artificialairway, though it can be provided noninvasively via tight-fitting nasal or full face masks. Noninvasive ventilation is particularly useful in patients with obstructive sleep apneaand neuromuscular disease who require support only part ofthe day, but it can also be used to assist ventilation continuously for patients in acute respiratory failure from a varietyof causes.


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Pediatrics_Nelson. No method of mechanical ventilation truly simulates natural breathing. All methods have their drawbacks and complications. Positive pressure is transmitted to the entire thoraxand may impede venous return to the heart during inspiration. The airways and lung parenchyma may be damaged byinflation pressures and high concentrations of inspired O2. In general, inflation pressures should be limited to those necessary to provide sufficient lung expansion for adequate ventilation and the prevention of atelectasis. Pressure-cycled and volume-cycled ventilators (conventional ventilation) are themost widely used modalities in pediatrics; however, high-frequency jet ventilation and high-frequency oscillatory ventilation are used often in neonatology and may be used inpatients with severe lung disease who are failing conventionalmechanical ventilation. Chapter 134 u Control of Breathing 461


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Pediatrics_Nelson. Chapter 134 u Control of Breathing 461 Ventilation is controlled primarily by central chemoreceptors located in the medulla that respond to intracellular pH and Pco2 levels (Fig. 134-1). To a lesser extent, ventilation is modulated by peripheral receptors located in the carotid and aortic bodies, which respond predominantly to Po2. The central receptors are quite sensitive. Small acute changes in Paco2 normally result in significant changes in minute ventilation. When the Pco2 is chronically elevated, the intracellular pH returns to normal levels because of compensatory increases in the bicarbonate level, and ventilatory drive is not increased. The peripheral receptors do not stimulate ventilation until the Pao2 decreases to approximately 60 mm Hg. These receptors become important in patients with chronic Paco2 elevation who may have a blunted ventilatory response to CO2.


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Pediatrics_Nelson. The output of the central respiratory center also is modulated by reflex mechanisms. Full lung inflation temporarily inhibits inspiratory effort in infants (Hering-Breuer reflex)through vagal afferent fibers. Other reflexes from the airways and intercostal muscles may influence the depth and frequency of respiratory efforts (see Fig. 134-1). An acute life-threatening event (ALTE) is defined as any unexpected and frightening change in condition characterized by PCO2, chemoreceptors sensory receptors (mechanoreceptors, + PO2 stretch, irritant and + PaO2, PaCO2