Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. A smaller retrospective study evaluating the performance of US in patients who had initially undergone multidetector CT interpreted by experienced readers showed that CT was 100% sensitive in the detection of tubo-ovarian abscesses (n = 9), and performing a follow-up US did not aid in diagnosis [40]. Although not specifically performed to evaluate for abscesses, a large prospective study evaluating the usefulness of CT and US in patients presenting with abdominal pain (n = 1,021) showed better sensitivity with CT in diagnosis of appendicitis (94% versus 76%, P < . 01) and diverticulitis (81% versus 61%, P = . 048) [41]. US and CT had similar sensitivities for the detection of acute cholecystitis. FDG-PET/CT Skull Base to Mid-Thigh Although generally not the primary modality of choice in the setting of acute or emergent abdominal pain, nuclear medicine studies could be used as an adjunct to inconclusive cross-sectional imaging. Because of its whole body imaging and sensitivity for infectious, inflammatory, and neoplastic processes, PET using the tracer fluorine-18- 2-fluoro-2-deoxy-D-glucose (FDG)/CT is useful in the setting of nonlocalized fevers of unknown origin, particularly if previous cross-sectional imaging did not yielded a source [42]. Nevertheless, there are no recent studies evaluating its use when patients present with symptoms localizing to the abdomen. Variant 2: Acute nonlocalized abdominal pain and fever. Postoperative patient. Initial imaging. In the setting of recent abdominal surgery, a variety of conditions could produce abdominal pain, including postoperative fluid collections, hemorrhage, vascular injuries, intestinal ileus, omental torsion/infarction, etc. However, the presence of concomitant fever is primarily concerning for a postoperative abscess and warrants cross-sectional imaging for further evaluation. In addition, patients who have had recent bowel manipulation or Acute Nonlocalized Abdominal Pain


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. resection could present with similar symptoms in the setting of postoperative visceral injury and/or anastomotic leaks. In this scenario, particular emphasis is often placed on ascertaining the integrity of an anastomosis, most often using CT with positive oral and IV contrast and/or fluoroscopic studies. Radiography Abdomen There are no recent studies evaluating the use of radiographs in the setting of nonlocalized abdominal pain and fever in the postoperative patient, and its role is limited in the detection of abscesses. Although it has been shown to have high sensitivity (90%) for detecting intra-abdominal foreign bodies and moderate sensitivity for detecting bowel obstruction (49%), it has low sensitivity for sources of abdominal pain and fever or abscess, which limits its role in this setting [15]. If there is concern for retained surgical instrument or sponge, a radiograph may be useful in this population because of the classic appearance of surgical sponge markers on radiographs. Fluoroscopy Although limited in the detection of abscesses, fluoroscopic examinations are useful in the evaluation of some intestinal postoperative leaks, particularly when there are equivocal findings on CT [47]. Fluoroscopic examinations can be augmented or complemented by the use of CT with positive oral contrast in the evaluation of a potential leak, as discussed below. CT has the added advantage of allowing for abscess drainage should nonoperative or endoscopic management be pursued in the setting of postoperative leaks. Fluoroscopy Contrast Enema In the setting of recent colorectal anastomoses, one study demonstrated that water-soluble enemas may have better sensitivity for detecting distal anastomotic leaks than CT, but neither was sensitive for a leak if the patient had a proximal colonic anastomosis [47]. Fluoroscopy Upper GI with SBFT The sensitivity of upper GI contrast examinations for detecting leaks after bariatric surgery varies among reports between 22% to 79% [48-51].


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. CT Abdomen and Pelvis CT of the abdomen and pelvis with IV contrast is often the first study and generally considered to be an optimal imaging modality for the evaluation of pain and suspected abscess in the postoperative patient. One study assessing the use of positive oral and IV contrast-enhanced CT scans obtained in all patients with suspected abscesses between 3 and 30 days demonstrated a similar diagnostic yield regardless of whether the scan was performed in the first postoperative week or later [23]. However, it is important to recognize that clinical suspicion can impact diagnostic yield. A retrospective study looking at postoperative patients after colorectal resection revealed that nearly 75% of patients with clinical concern for an infection will have a fluid collection, but many of these will not represent abscesses. Of the clinical, laboratory, and radiologic parameters studied, only a high index of clinical suspicion and close proximity of the fluid collection to the site of surgery were associated with predicting an infected collection [52]. In a retrospective review of elective pancreatic resections, intra- abdominal infections were diagnosed at a mean of 11.8 days following the procedure; notably, abdominal pain and peritonitis were uncommon presentations and early postoperative CT was encouraged in any patient presenting with fever and sepsis [53]. In the setting of colorectal anastomoses, one study evaluating 36 patients with proven leaks demonstrated water- soluble enema may have better sensitivity for detecting distal anastomotic leaks than CT (88% versus 12%, P <. 001), but in a very small number of patients (n = 10) neither was sensitive for a leak if the patient had a proximal colonic anastomosis [47]. CT can also help diagnose other causes of postoperative abdominal pain, including omental infarction or torsion [54].


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. Although IV contrast can help define and characterize postoperative fluid collections, in patients with severe renal insufficiency CT without IV contrast, but with positive oral Acute Nonlocalized Abdominal Pain contrast, it can be used as a substitute to screen for fluid collections and anastomotic leaks. Similarly, in patients with recent renal or liver transplantation in whom IV contrast cannot be administered, CT with oral contrast can be used to evaluate for intra-abdominal abscesses. CT with and without IV contrast typically is not necessary for this indication. Contraindications are not considered in the appropriateness assessment. MRI Abdomen and Pelvis There are no recent studies evaluating the use of MRI in the setting of nonlocalized abdominal pain and fever in the postoperative patient. CT is most commonly performed; however, MRI can be an accurate examination for detecting abdominal and pelvic abscesses when the image acquisition is optimized [35]. Although not specifically performed in postoperative patients, a retrospective review of 29 patients with known abscesses who underwent MRI admixed with 29 patients with simple noninfected ascites, MRI demonstrated 100% accuracy for 2 observers in the detection of abdominal abscesses in examinations performed with standard T2-weighted and postcontrast T1-weighted sequences. Interestingly, there were similar sensitivities for 2 observers when the images were reviewed with only T2-weighted and diffusion-weighted imaging (100% for observer 1, and 96.6% for observer 2), demonstrating the feasibility to detect and discriminate infected from noninfected fluid on noncontrast MRI [38]. In addition to appendicitis detection, in the retrospective study by Singh et al [37], the authors were able to detect 5 abscesses (2 tubo-ovarian abscesses) in female patients who underwent MRI presenting with acute pelvic pain.


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. In their prospective evaluation of noncontrast, rapid acquisition half-Fourier acquisition single-shot turbo spin-echo MRI in patients presenting with acute abdominal pain, Byott and Harris [36] demonstrated an overall accuracy of 99% (463 of 468 patients), including detection of diverticular and renal abscesses. The accuracy of MRI in detecting anastomotic leaks has not been studied. FDG-PET/CT Skull Base to Mid-Thigh There are limited recent studies evaluating the use of nuclear medicine imaging in the setting of nonlocalized abdominal pain and fever in the postoperative patient. FDG-PET/CT is useful in the workup of nonlocalized fevers of unknown origin, but in the setting of recent abdominal or pelvic surgery, normal postoperative inflammation could lead to false-positive results. As such, FDG-PET/CT could be used in a complementary fashion to other imaging studies when correlated with relevant surgical and clinical information and when other imaging studies are negative or inconclusive [42]. Nuclear Medicine Older studies performed in the 1980s to 1990s suggested gallium scans and indium and technetium leukocyte scans are useful in evaluating abdominal infections and abscesses when the CT scan is negative or equivocal [43- 45]. However, it is important to recognize that CT technology has significantly advanced since these studies were published. Older literature on technetium-labeled leukocytes also suggested a very high sensitivity and specificity for abdominal abscesses as well, although there are no adequate recent comparisons with CT [46]. In the setting of recent hepatobiliary surgery and specific concern for biliary ductal injury, cholescintigraphy can confirm the presence of a bile leak. Variant 3: Acute nonlocalized abdominal pain. Neutropenic patient. Initial imaging. In neutropenic patients, abdominal pain remains a diagnostic challenge because of the lack of classic clinical and laboratory signs of intra-abdominal disease [8].


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. Therefore, the diagnosis of acute abdomen may be delayed in these patients [7]. Neutropenia is being encountered more commonly in clinical practice and may be because of Acute Nonlocalized Abdominal Pain cytotoxic chemotherapy or immunosuppressive therapy. Colitidies and enteritidies are commonly found in this patient population, including clostridium difficile colitis, cytomegalovirus colitis, graft-versus-host disease, neutropenic enterocolitis, and bowel ischemia and perforation [8,56]. One study reported the most frequent causes of abdominal pain are neutropenic enterocolitis (28%) and SBO (12%) [8]. Atypical and opportunistic infections, chemotherapeutic-related mucosal injury, and tumors can all result in bowel pathology, and are commonly approached with IV contrast-enhanced CT as the initial imaging modality. Radiography Abdomen There are no recent studies that evaluate the use of radiography in the setting of acute nonlocalized or diffuse abdominal pain in the neutropenic patient. Radiography demonstrates low overall sensitivity in the detection of colitidies and enteritidies, and even low-dose CT demonstrates superior diagnostic yield in comparison with abdominal radiography [16]. Many authors suggest that radiographs have a limited role in the evaluation of nontraumatic abdominal pain in adults [17-22]. Fluoroscopy Contrast Enema There are no recent studies evaluating the use of contrast enema in the setting of acute nonlocalized or diffuse abdominal pain in the neutropenic patient. Fluoroscopy Upper GI with SBFT There are no recent studies evaluating the use of upper GI series with SBFT in the setting of acute nonlocalized or diffuse abdominal pain in the neutropenic patient. CT is often the initial imaging study to diagnose small bowel pathology in the immunocompromised patient, but occasionally barium studies may offer additional complementary information when mucosal lesions are small.


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. CT Abdomen and Pelvis CT with IV contrast is extremely useful in the evaluation of the neutropenic patient with abdominal pain secondary to its high spatial resolution and ability to display key imaging features [57]. Infectious and inflammatory processes of the small bowel and colon are well depicted by CT with IV contrast, which offers the additional advantage of depicting abscesses or perforations. Given the frequency of neutropenic enterocolitis (28%) and SBO (12%) in this setting, and as neutropenic enterocolitis is largely managed nonsurgically, an early and accurate diagnosis with CT can avoid unnecessary surgery and initiate appropriate medical management [8]. In addition, other abdominal infections, chemotherapeutic-related mucosal injury, and visceral tumors may be depicted by CT. CT without IV but with positive oral contrast can be used as an alternative if patients have severe renal insufficiency or a history of iodinated contrast allergies. Contraindications are not considered in the appropriateness assessment. Multiphasic CT imaging offers little additional benefit in absence of specific clinical indications related to liver or kidneys. MRI Abdomen and Pelvis There are no recent studies available to evaluate the use of MRI in acute nonlocalized or diffuse abdominal pain in the neutropenic patient. Although MRI with contrast may be used to evaluate SBO [58], there are no studies available to evaluate its diagnostic accuracy for neutropenic enterocolitis or other common colitidies or enteritidies in the neutropenic patient. MRI with contrast offers high soft-tissue contrast and the ability to administer gadolinium in patients with a history of allergic reaction to iodinated contrast material [58]. Specialized protocols (MR enterography or colonography) exist to interrogate the small bowel and colon and are mostly designed for use in patients with history of inflammatory bowel disease in the nonemergent setting.


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. For clinically stable patients who are not able to undergo CT and in whom the bowel is a primary diagnostic consideration, MRI without and with contrast (and in particular MR enterography) may be an alternative imaging option. US Abdomen There are no recent studies available for the evaluation of US in the setting of acute nonlocalized abdominal pain in the neutropenic patient. US may serve as a fast way of evaluating the liver, kidneys, and biliary tree, including the evaluation of HIV cholangiopathy. In the HIV-infected patient presenting with prolonged fever, one study demonstrated abdominal US successfully identifies liver lesions and splenic microabscesses in 14% of the presenting population [59]. Nuclear Medicine and FDG-PET/CT Skull Base to Mid-Thigh There are no recent studies evaluating the use of nuclear medicine imaging in the setting of acute abdominal pain in the neutropenic patient, and there are no specific indications for its use in this setting. Because of its whole Acute Nonlocalized Abdominal Pain Variant 4: Acute nonlocalized abdominal pain. Not otherwise specified. Initial imaging. The causes of nonlocalized, nontraumatic abdominal pain are extensive, and, as such, imaging needs to be broad enough to visualize the entire abdomen and pelvis, screening for visceral, solid organ, and vascular abnormalities. Imaging strategies are similar to those in patients who have concomitant fever, as many of the sources of pain overlap. CT is frequently performed first. Fluoroscopy Contrast Enema There are no recent studies evaluating the use of contrast enema imaging in the setting of nonlocalized abdominal pain, and there are no specific indications for its use in this setting. Endoscopy is the preferred initial examination of the stomach and colon in patients suspected of having inflammatory bowel disease.


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. CT Abdomen and Pelvis CT can be performed without and/or with IV contrast and with or without oral contrast, depending on localizing symptoms and/or laboratory findings. In general, a single-phase IV contrast-enhanced examination is performed as additional precontrast and postcontrast images are not required for diagnosis. Abdominal CT without the use of oral or IV contrast has been advocated as an alternative to abdominal radiographs for evaluating appendicitis [17,24]. However, the use of IV contrast increases the spectrum of detectable pathology [25,26]. Unless otherwise specified, the subsequent discussion of CT refers to IV contrast-enhanced CT. Contraindications are not considered in the appropriateness assessment. Many institutions no longer routinely use oral contrast because of the associated delay in scan acquisition and departmental and ED throughput balanced against questionable diagnostic advantage [27-30]. Positive oral contrast may help improve confidence in identifying bowel-related pathology; however, advances in CT technology with multiplanar reformations can also improve diagnostic confidence in patients with abdominal pain [61-63]. Several studies have shown that CT improves the final diagnosis and management of patients who present with abdominal pain [5,24,31,64-67]. A prospective trial of 547 patients presenting to the ED with abdominal pain demonstrated that CT altered the diagnosis in 54% of patients and frequently changed disposition patterns, with a greater proportion of patients discharged in lieu of admission for observation [68]. Other studies have shown that CT outperforms clinical diagnosis [69,70]. Additionally, the use of CT in patients with acute abdominal pain In a prospective study of 584 ED patients presenting with nontraumatic abdominal pain, CT was shown to change the diagnosis, improve diagnostic certainty, and affect potential patient management decisions [31].


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. In this study, CT was used to alter the leading diagnosis in 49% of the patients and increase mean physician diagnostic certainty from 70.5% (pre-CT) to 92.2% (post-CT). The management plan was changed by CT in 42% of the patients. In another study of 522 young adult patients presenting to the ED with abdominal pain, no laboratory test was sufficient to offer reassurance that a CT was not necessary [72]. One retrospective study evaluating 333 ED patients with acute abdominal pain and an abdominal CT demonstrated no significant difference in accuracy if the radiologist was blinded to relevant clinical or laboratory information (approximately 85%) [73]. CT is highly accurate in determining the site of visceral perforation, particularly in the setting of upper intestinal perforation, which could impact the surgical approach [74]. With an aging United States population and the relatively high frequency of ED presentations for acute abdominal pain, multiple recent studies have looked at the imaging evaluation of elderly patients, particularly the range of diagnoses and the use of abdominal CT. Depending on the article, elderly is defined as ranging from >65 years of age to >80 years of age. In this subset of the population, many laboratory tests are nonspecific and may be normal despite serious abnormalities [4-6]. Many authors advocate for liberal use of CT in elderly patients [4,75,76]. The most common causes of abdominal pain in elderly patients undergoing a CT examination are different than those in younger patients. One retrospective study looked at the use of CT in 464 patients >80 years of age and found the most common diagnoses were SBO (18%), diverticulitis (9%), nonischemic vascular emergencies including abdominal aortic aneurysm and dissection (6%), bowel ischemia (4%), appendicitis (3%), and colonic obstruction (2%). These diagnoses were clinically unsuspected in 43% of patients [4].


Acute Nonlocalized Abdominal Pain

Acute Nonlocalized Abdominal Pain. Another study evaluating the incidence of acute mesenteric ischemia in patients >75 years of age demonstrated a high age-specific incidence in this population, with a greater incidence of acute mesenteric ischemia than acute appendicitis or ruptured abdominal aortic aneurysms. These patients often have a nonspecific presentation and authors suggest use of dual-phase (arterial and portal venous phase) CT with contrast to ensure adequate evaluation of mesenteric vasculature in all patients >75 years of age presenting with acute abdominal pain [75]. Acute Nonlocalized Abdominal Pain MRI Abdomen and Pelvis MRI has been shown to provide clinically useful information for rapid diagnosis of acute bowel pathology [35,58,84,85] and the following gynecological emergencies: ovarian hemorrhage, ectopic pregnancy, tumor rupture, torsion, hemorrhage, infarction, and pelvic inflammatory disease [36,86,87]. Although MRI has longer acquisition times relative to CT, improvements in technology combined with tailored abdominal protocols could be performed in 10 minutes or less [36,88]. One prospective study looking at the use of noncontrast MRI in 468 patients with acute abdominal pain (excluding renal colic), with an image acquisition time of under 2 minutes, showed an overall accuracy of 99% in diagnosing diseases ranging from acute bowel inflammation, obstruction, and pancreaticobiliary diseases, to renal inflammation and gynecological processes [36]. In the setting of acute pelvic pain, MRI with contrast can accurately diagnose acute appendicitis, ovarian torsion, and other adnexal diseases [37]. Because useful information can be obtained without contrast, MRI, when available, has been shown to be a reliable next step following US in the imaging of pregnant patients [89]. MRI is becoming a favored, invaluable problem-solving modality used in the imaging of pregnant patients because it avoids many of the drawbacks of US and CT.