Seizures and Epilepsy

Seizures and Epilepsy. Pseudoresponse can also be problematic, with an apparent decrease in contrast enhancement in a tumor due to changes in vascular permeability as opposed to true tumor response also resulting in a complicated interpretation [39]. MR spectroscopy and MR perfusion can be effective adjunct imaging examinations to complement conventional MRI [38]. HMPAO SPECT or SPECT/CT Brain Ictal and Interictal There is no relevant literature regarding the use of SPECT or SPECT/CT in the evaluation of known seizure disorder with history of tumor unless in the setting of presurgical planning. Variant 6: Known seizure disorder. Surgical candidate or surgical planning. CT Head Evaluation of seizures was greatly advanced by the clinical introduction of CT in the early 1970s [40,41] because of its cross-sectional capabilities that were not possible with radiographs. However, CT is outperformed by MRI in Seizures and Epilepsy having less contrast resolution between gray and white matter differentiation [16], and overall CT is less sensitive to detecting lesions compared with MRI [41,42]. CT is useful in the assessment of calcification pathologies, such as tuberous sclerosis and oligodendrogliomas [23]. CT can be used for stereotactical surgical planning, and high- resolution CT can be used to assess the position of subdural grid or depth electrodes [23], which can be done without IV contrast administration. Noncontrast CT and MRI have been advocated equally for accurate electrode localization [43]. FDG-PET/CT Brain Clinical FDG-PET/CT provides a measure of glucose uptake and thus a measure of metabolism and has been shown to be highly sensitive in the presurgical localization of epileptogenic foci [8]. A seizure focus will typically manifest as a focus of hypometabolism on interictal (between episodes of seizure activity) PET examinations. One study demonstrated that presurgical ipsilateral PET hypometabolism showed predictive value of 86% for good surgical outcomes [44].


Seizures and Epilepsy

Seizures and Epilepsy. Presurgical FDG-PET also provides information regarding the functional deficit zone, the area of the brain that shows abnormal function during the interictal period. FDG-PET can identify focal abnormalities in the setting of a negative anatomic MRI brain scan [16]. Poor seizure outcomes following surgery have been described in the setting of bilateral temporal lobe hypometabolism in TLE [8]. A limitation of FDG-PET is the lack of precision in defining the margins of the epileptogenic zone [8]. Comparison of interictal PET and ictal SPECT demonstrated localization of lesions in 77.7% and 7.3% of patients, respectively [45]. FDG-PET, combined with other localizing modalities, such as perfusion ictal-interictal SPECT and MRI gray matter segmentation, has shown improved abilities to detect and predict the extent of epileptic foci [28]. FDG-PET co-registered with MRI may be an effective adjunctive study as it has been shown that MRI gray matter segmentation co-registered with FDG-PET resulted in higher correspondence to intracranial EEG than without segmentation [46]. MEG MEG records brain electrical activity, which can be localized in 3-D by using detectors and induction coils in a superconducting environment [47]. In contrast to EEG, MEG does not suffer from deterioration of signals due to the skull and scalp [48]. In one study, 85% of patients with concordant and specific MEG findings were seizure- free following surgery, compared with only 37% of individuals with MEG findings that were nonspecific or discordant with the region of resection [49]. One of the largest cases series of MEG utilization in 455 patients demonstrated a 70% sensitivity in detecting epileptic activity [50]. Though there have been significant advances in source localization techniques, MEG is still performed in only a minority of presurgical evaluation of epilepsy, and the clinical value of MEG in surgical epilepsy treatment is less clear compared with MRI [48].


Seizures and Epilepsy

Seizures and Epilepsy. Nevertheless, it can be useful as a complementary modality in assessment of location of seizures in preoperative brain mapping as well as identification of eloquent cortex to determine safe resection margins [51]. MRI Functional (fMRI) Head The utility of fMRI has been well described in the literature in the setting of presurgical evaluation of patients with epilepsy [44,52] and perhaps even more so in the setting of MRI-negative epilepsy [18]. For patients with drug- resistant focal epilepsy, functional neuroimaging techniques, such as FDG-PET, ictal SPECT, or fMRI, may assist in surgical planning, especially in patients with MRI-negative epilepsy, whose prognosis for a seizure-free outcome after surgery is worse than for patients with an epileptogenic lesion on structural MRI. fMRI demonstrated 89% concordance in language lateralization with an intracarotid amobarbital procedure (IAP) with right TLE and 85% for left TLE [53]. The same study also demonstrated 83% concordance with IAP in language lateralization extra- TLE [53], and as such, fMRI can be considered as a replacement for IAP for language lateralization [52]. One study demonstrated that strong left frontal activation was predictive of postresection decline [53], and thus fMRI can be considered for predicting postsurgical language deficits in presurgical evaluation for possible temporal lobectomy [52]. fMRI can be an option to lateralize memory functions with good correlation on one study (r = 0.31; P = . 007) between hippocampal fMRI laterality index and IAP memory laterality index [54]; however, conflicting data showing no correlation were also found in the literature [55]. fMRI using model paradigms is a promising method to noninvasively predict memory decline [56]. MRI Head MRI demonstrates excellent gray-white matter differentiation and multiplanar imaging capability, characteristics that contribute to greater sensitivity and accuracy of MRI compared with CT [8,31].


Seizures and Epilepsy

Seizures and Epilepsy. As a result, MRI has become the modality of choice for high-resolution structural imaging in epilepsy, with the use of IV contrast dependent on the underlying etiology of the seizures. Dedicated seizure protocols and acquisition on 3T magnets are important Seizures and Epilepsy considerations to improve lesion detection [31]. MRI is the study of choice in the assessment of structural lesions that are potentially resectable [16]. It can define the epileptogenic zone, that is, the minimum amount of cortex that should be resected to provide seizure-free outcome [16]. It should be noted that 20% to 30% of temporal epilepsy and 20% to 40% of patients with extra-TLE have no clear lesion seen on MRI [17]. Nevertheless, patients are more likely to be seizure-free when focal circumscribed lesions are identified on presurgical MRI compared with those patients who do not have these lesions [57,58]. Noncontrast CT and MRI have been advocated equally for accurate electrode localization [43]. HMPAO SPECT or SPECT/CT Brain Ictal and Interictal SPECT that uses perfusion agents like Tc-99m-HMPAO (hexamethyl-propylamine-oxime) or Tc-99m-neurolite provides an assessment of regional cerebral blood flow rather than brain metabolism. A seizure focus is typically demonstrated as an area of hypoperfusion on interictal examinations and hyperperfusion on ictal examinations [6]. The utility of isolated interictal cerebral perfusion assessment in patients without an anatomic imaging abnormality is limited, with one study finding that of all patients with seizures only 60% of interictal cerebral perfusion imaging was abnormal [59]. However, perfusion SPECT is complementary to structural imaging in presurgical planning. Statistical ictal SPECT co-registered to MRI was noted to identify a hyperperfusion focus in 84% of patients compared with 66% using subtraction ictal SPECT co-registered to MRI for seizure localization before TLE surgery and may be indicated for these cases [43].


Crohn Disease Child

Crohn Disease Child.  Introduction/Background Crohn disease is an inflammatory condition of the gastrointestinal tract with episodes of exacerbation and remission occurring in children, adolescents, and adults. In a genetically predisposed patient, the underlying mechanism is due to an inappropriate inflammatory reaction to intestinal flora [1-3]. Along with ulcerative colitis, Crohn disease is a common inflammatory bowel disease (IBD) with increasing frequency. The prevalence of IBD is 100 to 200 cases per 100,000 children with approximately 10 new cases per 100,000 children diagnosed each year in the United States [4]. Twenty-five percent of all IBD patients are diagnosed prior to 20 years of age [4]. Of these children with IBD, 18% were diagnosed before 10 years of age [4]. Unlike ulcerative colitis, Crohn disease is characterized by transmural granulomatous inflammation as well as discontinuous or skip lesions that can occur anywhere in the gastrointestinal tract. Any portion of the gastrointestinal tract may be involved, most frequently the small bowel and colon, yet perianal Crohn disease is another common manifestation occurring in 15% to 25% of pediatric patients with Crohn disease [5,6]. Crohn disease diagnosis and treatment depend upon a combination of clinical, laboratory, endoscopic, histological, and imaging findings. Appropriate use of imaging provides critical information in the settings of diagnosis, assessment of acute symptoms, disease surveillance, and therapy monitoring. Although portions of the alimentary tract are accessible by either upper endoscopy or ileocolonoscopy, imaging is necessary for many reasons, including assessment of the bowel (particularly small bowel) not amenable to endoscopy, detection of transmural disease without overlying mucosal abnormality, assessment of extraluminal penetrating and extraintestinal disease, and when diagnostic information is sought without invasive endoscopy [1].


Crohn Disease Child

Crohn Disease Child. For patients with high clinical concern for Crohn disease and both conventional endoscopy and imaging are unrevealing, video capsule endoscopy may also be considered [4]. Special Imaging Considerations Both MR enterography (MRE) and CT enterography (CTE) require oral contrast material ingestion by the patient. Sufficient bowel distention is necessary to decrease bowel collapse, which can imitate or obscure Crohn disease [7]. Commonly used oral contrast agents for both MRE and CTE include sugar alcohol-based beverages, polyethylene glycol, and low-concentration barium suspensions. Oral contrast administration ultimately depends upon institutional preference. The total volume of oral contrast ingested typically ranges from 900 to 1,500 mL administered over 45 to 60 minutes before the examination, with total volume based on patient weight [7]. Even in the absence of specific concern for perianal fistula, when imaging with MRE/CTE (or nonenterography MR/CT), coverage should include the perineum to facilitate detection of perianal Crohn disease. If discovered, more focused additional imaging of the perineum may be considered (as discussed in Variant 4). Another imaging consideration for perianal Crohn disease is MRI field strength. Although children may be imaged using either 1.5T or 3T MRI, The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org Crohn Disease-Child the higher field strength (3T) provides greater signal-to-noise ratio that is advantageous for delineating penetrating Crohn disease anatomic location in relation to anal sphincter complex [6].


Crohn Disease Child

Crohn Disease Child. MR/CT enteroclysis requires placement of a postpyloric balloon-tipped tube, most often a nasoduodenal tube, to allow enteric contrast infusion directly into the small bowel. Enteroclysis is performed under fluoroscopy with subsequent patient transfer to MR or CT afterward, which can result in logistical challenges. A study directly comparing MR enteroclysis and MRE in adult patients with suspected or established Crohn disease showed both techniques to be equivalent for detecting terminal ileal inflammation, small bowel fistulae, and strictures [8]. In rare circumstances when enteroclysis may be considered (eg, attempt at uniform small bowel distention to assess for a partial stricture), enteroclysis has been shown to be effective in pediatric patients [9]. However, because enteroclysis is substantially more invasive than enterography, is less well tolerated than enterography, and is without clear added benefit, it is presently infrequently used in children. CTE provides high diagnostic performance for evaluation of Crohn disease activity in pediatric patients, as in adults, with a sensitivity >80% and a specificity >85% compared with endoscopic and histologic reference [11-13]. These studies directly compared CTE and MRE and did not find any significant difference in performance between the two modalities. Furthermore, a meta-analysis based on 290 patients from 6 studies showed sensitivity and specificity in detecting active small bowel Crohn disease was 85.8% and 83.6%, respectively, with an area under the curve (AUC) of 0.898 [14]. CTE imaging features of active Crohn disease inflammation are very similar to those reported Crohn Disease-Child for MRE and include mural (eg, wall thickening and hyperenhancement) and perienteric (eg, engorged vasa recta, fibrofatty proliferation, adenopathy) features of disease [15].


Crohn Disease Child

Crohn Disease Child. A study comparing the performance of different CTE and MRE imaging features compared with histologic reference showed that mural features of disease (wall thickening and hyperenhancement) performed better than perienteric features in evaluating activity and may be more reliable features in cases where some but not all features of activity are present [16]. FDG-PET/CT Skull Base to Mid-Thigh At the present time, there is a paucity of larger clinical studies published for fluorine-18-2-fluoro-2-deoxy-D- glucose (FDG)-PET/CT in the setting of Crohn disease, particularly in children, and an absence of literature to support this as an initial imaging modality prior to diagnosis. Adding metabolic information from FDG-PET to anatomic CT imaging shows the potential to further diagnostic accuracy in children. A meta-analysis of 7 studies with a total of 219 patients (3 studies with 93 patients were pediatric focused) on a per segment basis showed sensitivity was 85%, specificity 87%, and area under the receiver operating characteristic curve was 0.93. PET/CT may be particularly helpful to assess the level of active inflammation from fibrosis [18]. One pediatric study with 23 patients showed a sensitivity and specificity for the terminal ileum of 89% and 75%, respectively [19]. A limitation that must be noted is physiological distribution of FDG, including normal uptake in the terminal ileum, which may compromise PET imaging of patients with IBD. Although potentially promising, additional development for PET/CT in children is necessary. If performing FDG-PET/CT for the evaluation of Crohn disease, the area of coverage from skull base to mid-thigh may be sufficient for bowel evaluation, although some institutions do perform full-body imaging (from vertex to toes); therefore area of coverage may be determined according to institutional practices.


Crohn Disease Child

Crohn Disease Child. Fluoroscopy Contrast Enema Colonoscopy is the most useful modality for evaluation of the colon in patients with suspected or known Crohn disease involving the colon [2]. Fluoroscopy contrast enema is uncommonly used in current practice. An institutional study confirmed this decline in which the average number of contrast enema per Crohn disease patients per year dropped from 0.05 in 2001 to 0.01 in 2010 [20]. Fluoroscopy contrast enema, however, may remain an option if selected problem solving is necessary, such as stricture assessment during contrast injection [21]. Fluoroscopy Upper GI Series with Small Bowel Follow-Through Using fluoroscopy small bowel follow-through (SBFT) with barium is a historically well-established modality for small bowel evaluation [2]. There is, however, a significant decrease in use of SBFT with current widespread use of cross-sectional imaging modalities including MRI and CT. Although fluoroscopy SBFT allows accurate intraluminal and mucosal assessment, bowel wall thickness among other signs cannot be directly visualized. Additionally, although internal fistulas may be visualized, extraluminal pathologies including abscess formation may only be indirectly inferred. In a study of 87 pediatric patients with IBD utilization histology as criterion standard, 31% of patients had pathology identified on MRI not visualized on SBFT. In this study, the SBFT sensitivity and specificity were 76% and 67%, respectively, whereas MRI demonstrated greater sensitivity and specificity of 83% and 95%, respectively [22]. Fluoroscopy SBFT, however, does remain an option if problem solving is necessary, such as cutaneous fistula evaluation [21]. Fluoroscopy SBFT may also serve as an alternative to MRI and CT to avoid sedation, particularly in younger children. Crohn Disease-Child


Crohn Disease Child

Crohn Disease Child. The role of MRE in this scenario includes diagnosis, delineation of disease extent including discrimination of Crohn disease from ulcerative colitis, depiction of extraintestinal manifestations of Crohn disease, and detection of penetrating disease complications that may influence treatment decisions. The latter may include fistulae that may be indicators for biologic therapy or abscess formation that may necessitate antibiotics and/or drainage. Evaluation of small bowel disease is an especially important role for MRE given the limitations of optical endoscopy in small bowel accessibility and visualization, particularly when Crohn disease terminal ileitis causes luminal narrowing [1]. Radiography Abdomen Visualization of bowel pathology is limited on abdominal radiographs, which often restricts utilization for initial diagnoses. US Abdomen Ultrasound (US) abdomen can be used for imaging Crohn disease during initial diagnosis. US may be a suitable alternative for evaluation of the terminal ileum in younger children who would otherwise require sedation for MRE Crohn Disease-Child or CTE examinations [21]. Sonographic technique requires a systematic assessment of the entire bowel including terminal ileum, colon, and more proximal small bowel. All four quadrants of the bowel should be evaluated in both the transverse and longitudinal planes [32]. Color Doppler US is also performed to facilitate hyperemia assessment. Sonographic features include abnormal bowel wall thickening (>3 mm in children), alteration of bowel wall signature, adjacent fatty proliferation, hyperemia, and engorgement of the vasa recta [32]. Patient features may adversely affect US including elevated body mass index as well as bowel gas resulting in shadowing. In the setting of pediatric Crohn disease though, obesity is less likely given that many patients have diminished nutrition [32]. The detection of alternative diagnoses is also decreased compared with CT or MRI.


Crohn Disease Child

Crohn Disease Child. In addition to routine abdominal US without contrast, further discussed below, oral contrast material may be administered by some institutions. Intraluminal oral contrast administration, most commonly with polyethylene glycol, is also termed small intestine contrast ultrasonography (SICUS). SICUS may heighten sensitivity and decrease radiologist interpretation variability [2]. A meta-analysis indicated a pooled sensitivity of 88% and sensitivity of 86% [37]. However, this analysis did not compare SICUS to US without oral contrast administration, and therefore the added benefit was not ascertained. In a prospective pediatric study of 25 patients, the SICUS sensitivity in the terminal ileum was 94%, proximal ileum 80%, and jejunum 92%, with authors concluding SICUS was an effective option for imaging the small bowel [38]. Additional pediatric-focused literature for SICUS is more limited, and direct comparison with and without oral contrast is currently lacking. At present, administration of oral contrast during abdominal US is uncommon in clinical practice. US Abdomen With IV Contrast IV contrast-enhanced US (CEUS) assesses the microbubble enhancement pattern predominately of the bowel wall. Multiple CEUS agents are available, all with strong safety profiles. Following IV administration of these microbubbles, high-frequency sonographic waves cause oscillation of the microbubble core gas resulting in pronounced conspicuity. Quantitative features, such as time to peak enhancement, maximum enhancement, and areas under the enhancement curve, may be determined to supplement analysis. Studies in adult populations found that quantitative analysis facilitated differentiation of inflammatory from fibrostenotic strictures [39] and that both increased maximum peak intensity and wash in slope coefficient was indicative of active disease [40]. A meta-analysis of CEUS based on 8 studies with 428 adult patients indicated a sensitivity of 93%, a specificity of 87%, and an AUC of 0.96 [41].


Crohn Disease Child

Crohn Disease Child. A different meta-analysis of CEUS of 8 articles with a total of 332 adult patients indicated a pooled sensitivity of 94% and specificity of 79% [42]. Also, there is a paucity of literature that reveals added benefit beyond US without IV contrast. One adult study, however, did show that quantitative CEUS parameters integrated with grayscale US with color Doppler imaging reduced indeterminate results [43]. Currently, there is a lack of studies using CEUS in children. This fact, combined with a paucity of literature supporting added benefit of CEUS beyond routine US, limits CEUS appropriateness at the present time as the initial imaging study. However, future studies are anticipated given the CEUS safety profile and adult literature. CEUS will likely be an area of future development for children with Crohn disease. Another avenue of potential future development that may supplement CEUS is determining the role to US shear wave elastography in pediatric patients, because literature is starting to emerge in adults [44]. WBC Scan Whole Body Tc-99m-hexamethyl propylene amine oxime-labeled white blood cell (Tc-99m HMPAO WBC) scan studies show sensitivities from 75% to 94% and specificities from 92% to 99% for intestinal inflammation in children [45]. More recently, Chroustova et al [46] found a sensitivity of 89% and specificity of 91% in 85 children. Although the Crohn Disease-Child diagnostic parameters of a WBC scan whole body are useful for both diagnosis and disease activity assessment, significant practical limitations exist. One disadvantage is the decreased ability to detect and evaluate alternative diagnoses. Other significant disadvantages are the technical aspects, including the volume of blood required for labeling, longer acquisition times, and limited usage for initial diagnosis. Variant 2: Child. Known Crohn disease, suspected acute exacerbation. Initial Imaging.


Crohn Disease Child

Crohn Disease Child. In this variant, the child already has an established diagnosis of Crohn disease, and the patient presents with acute worsening of symptoms. The primary concern is active inflammation resulting in a Crohn disease complication such as fistula development, abscess, or bowel perforation. Transmural inflammation and/or fibrosis may also result in stricture formation associated with luminal stenosis and bowel obstruction. Acute exacerbation of extraintestinal manifestations such as nephrolithiasis, cholelithiasis, and primary sclerosing cholangitis may also be detected [1]. In this variant, the clinical suspicion for other etiologies of abdominal pain is low. CTE provides high diagnostic performance for evaluation of Crohn disease activity in pediatric patients, as in adults, with a sensitivity >80% and a specificity >85% compared with endoscopic and histologic reference [11-13]. These studies directly compared CTE and MRE and did not find any significant difference in performance between the two modalities. Furthermore, a meta-analysis based on 290 patients from 6 studies showed sensitivity and specificity in detecting active small bowel Crohn disease was 85.8% and 83.6%, respectively, with the AUC of 0.898 [14]. CTE imaging features of active Crohn disease inflammation are very similar to those reported for MRE and include mural (eg, wall thickening and hyperenhancement) and perienteric (eg, engorged vasa recta, fibrofatty proliferation, lymphadenopathy) features of disease [15]. A study comparing the performance of different CTE and MRE imaging features compared with histologic reference showed that mural features of disease (wall thickening and hyperenhancement) performed better than perienteric features in evaluating activity and may be more reliable features in cases in which some but not all features of activity are present [16].


Crohn Disease Child

Crohn Disease Child. FDG-PET/CT Skull Base to Mid-Thigh It would be unusual for FDG-PET/CT for Crohn disease to be performed in an acute setting with absence of supporting literature for assessment of acute exacerbation in children. Crohn Disease-Child Fluoroscopy Contrast Enema Colonoscopy is the most useful modality for evaluation of the colon in patients with suspected or known Crohn disease involving the colon [2]. Fluoroscopy contrast enema is uncommonly used in current practice, given its limited ability to evaluate the small bowel. An institutional study confirmed this decline in which the average number of contrast enema per Crohn disease patients per year dropped from 0.05 in 2001 to 0.01 in 2010 [20]. Fluoroscopy contrast enema, however, may remain an option if selected problem solving is necessary, such as stricture assessment during contrast injection [21]. Fluoroscopy Upper GI Series with Small Bowel Follow-Through Using fluoroscopy SBFT with barium is a historically well-established modality for small bowel evaluation [2]. There is, however, a significant decrease in use of SBFT with current widespread use of cross-sectional imaging modalities including MRI and CT. Although fluoroscopy SBFT allows accurate intraluminal and mucosal assessment, bowel wall thickness among other signs cannot be directly visualized. Additionally, although internal fistulas may be visualized, extraluminal pathologies including abscess formation may only be indirectly inferred. In a study of 87 pediatric patients with IBD utilization histology as criterion standard, 31% of patients had pathology identified on MRI not visualized on SBFT. In this study, the SBFT sensitivity and specificity were 76% and 67%, respectively, whereas MRI demonstrated greater sensitivity and specificity of 83% and 95%, respectively [22]. Fluoroscopy SBFT, however, does remain an option if problem solving is necessary, such as cutaneous fistula evaluation [21].


Crohn Disease Child

Crohn Disease Child. Fluoroscopy SBFT may also serve as an alternative to MRI and CT to avoid sedation, particularly in younger children. The role of MRE in this scenario include delineation of disease extent, depiction of extraintestinal manifestation of Crohn disease, and detection of penetrating disease complications that may influence treatment decisions (eg, fistulae that may be indicators of biologic therapy or abscess formation that may necessitate antibiotics and/or drainage). Evaluation of small bowel disease is an especially important role for MRE given the limitations of optical endoscopy in small bowel accessibility and visualization, particularly when Crohn disease terminal ileitis causes luminal narrowing [1]. MRI Abdomen and Pelvis MRI of the abdomen and pelvis without oral contrast enterography technique can be considered for Crohn disease patients who may be unable to tolerate sufficient oral contrast, particularly for those with acute abdominal symptoms Radiography Abdomen Visualization of bowel pathology is limited on abdominal radiographs, which restricts utilization. Although cross- sectional techniques have largely supplanted the previous role, radiographs may continue to provide diagnostic information for severely ill children, including those with bowel perforation or bowel obstruction. A recent study of 643 abdominal radiographs (16% were >17 years of age) revealed four cases of pneumoperitoneum, two cases of obstruction, and no cases of toxic megacolon, indicating that these scenarios are uncommon [47]. If present, the information may help modify additional imaging or emergent clinical management, such as additional CT for emergent surgical planning in the setting of a bowel perforation. If radiography is performed for emergent clinical assessment, a left lateral decubitus or upright radiograph should be performed in addition to a supine radiograph for pneumoperitoneum assessment. US Abdomen US abdomen can be used for imaging Crohn disease during acute exacerbation.


Crohn Disease Child

Crohn Disease Child. US may be a suitable alternative for evaluation of the terminal ileum in younger children who would otherwise require sedation for MRE or CTE examinations [21]. Sonographic technique requires a systematic assessment of the entire bowel including terminal ileum, colon, and more proximal small bowel. All four quadrants of the abdomen should be evaluated in both the transverse and longitudinal planes [32]. Color Doppler US is also performed to facilitate mural hyperemia assessment. Sonographic features include abnormal bowel wall thickening (>3 mm in children), alteration of bowel wall signature, adjacent fatty proliferation, hyperemia, and engorgement of the vasa recta [32]. Patient features may adversely affect US including elevated body mass index as well as bowel gas resulting in shadowing. In the setting of pediatric Crohn disease, though, obesity is less likely given that many patients have impaired nutrition [32]. The detection of alternative diagnoses is also decreased compared with CT or MRI. US Abdomen With IV Contrast Currently, there is a lack of studies to support using CEUS in children in the acute or emergent setting. WBC Scan Whole Body Tc-99m HMPAO WBC scan has very significant practical limitations in the acute setting. One disadvantage is the decreased ability to detect and evaluate alternative diagnoses. Other significant disadvantages are the technical aspects including volume of blood required for labeling and longer acquisition times limiting usage in this variant. Crohn Disease-Child CTE provides high diagnostic performance for evaluation of Crohn disease activity in pediatric patients, as in adults, with a sensitivity >80% and a specificity >85% compared with endoscopic and histologic reference [11-13]. These studies directly compared CTE and MRE and did not find any significant difference in performance between the two modalities.


Crohn Disease Child

Crohn Disease Child. Furthermore, a meta-analysis based on 290 patients from 6 studies showed sensitivity and specificity in detecting active small bowel Crohn disease was 85.8% and 83.6%, respectively, with the AUC of 0.898 [14]. CTE imaging features of active Crohn disease inflammation are very similar to those reported for MRE and include mural (eg, wall thickening and hyperenhancement) and perienteric (eg, engorged vasa recta, fibrofatty proliferation, adenopathy) features of disease [15]. A study comparing the performance of different CTE and MRE imaging features compared with histologic reference showed that mural features of disease (wall thickening and hyperenhancement) performed better than perienteric features in evaluating activity and may be more reliable features in cases in which some but not all features of activity are present [16]. Although relative radiation levels are beyond the purview of this discussion, they are listed in the tables at the beginning of the document and may be considered by the requesting physician particularly in the setting of disease surveillance and therapy monitoring in children. For additional information, please see the Relative Radiation Level Information section at the end of this document. Crohn Disease-Child FDG-PET/CT Skull Base to Mid-Thigh Combining metabolic information from FDG-PET with anatomic CT imaging shows potential to further diagnostic accuracy in children. A meta-analysis of 7 studies with a total of 219 patients (3 studies with 93 patients were pediatric focused) on a per segment basis showed sensitivity was 85%, specificity 87%, and area under the receiver operating characteristic curve was 0.93. PET/CT may be particularly helpful to assess the level of active inflammation from fibrosis [18]. One pediatric study with 23 patients showed a sensitivity and specificity for the terminal ileum of 89% and 75%, respectively [19]. At the present time, however, there is a paucity of larger clinical studies published, particularly in children.


Crohn Disease Child

Crohn Disease Child. In selected monitoring or surveillance scenarios, however, FDG-PET/CT may supplement existing imaging to further help determine the presence of metabolic activity (eg, stricture assessment for surgical planning) [48,49]. A limitation that must be noted is physiological distribution of FDG, including normal uptake in terminal ileum, which may compromise PET imaging of patients with IBD. If performing FDG-PET/CT for the evaluation of Crohn disease, the area of coverage from skull base to mid-thigh may be sufficient for bowel evaluation; however, some institutions do perform full-body imaging (from vertex to toes); therefore the area of coverage may be determined according to institutional practices. Fluoroscopy Contrast Enema Colonoscopy is the useful study for evaluation of the colon in patients with suspected or known Crohn disease involving the colon [2]. Fluoroscopy contrast enema is uncommonly used in current practice because of its limited ability to evaluate the small bowel. Fluoroscopy contrast enema, however, may remain an option if selected problem solving is necessary, such as stricture assessment during contrast injection [21]. Fluoroscopy Upper GI Series with Small Bowel Follow-Through Utilizing fluoroscopy SBFT with barium is a historically well-established modality for small bowel evaluation [2]. There is, however, a significant decrease in use of SBFT with current widespread use of cross-sectional imaging modalities including MRI and CT. Although fluoroscopy SBFT allows accurate intraluminal and mucosal assessment, bowel wall thickness among other signs cannot be directly visualized. Additionally, although internal fistulas may be visualized, extraluminal pathologies including abscess formation may only be indirectly inferred. In a study of 87 pediatric patients with IBD utilization histology as criterion standard, 31% of patients had pathology identified on MRI not visualized on SBFT.


Crohn Disease Child

Crohn Disease Child. In this study, the SBFT sensitivity and specificity were 76% and 67%, respectively, whereas MRI demonstrated a greater sensitivity and specificity of 83% and 95%, respectively [22]. Fluoroscopy SBFT, however, does remain an option if problem solving is necessary, such as cutaneous fistula evaluation [21]. Fluoroscopy SBFT may also serve as an alternative to MRI and CT to avoid sedation, particularly in younger children. Crohn Disease-Child gadolinium beyond non-IV contrast-enhanced MRE for detection of active IBD in pediatric patients [29]. Additionally, a study of IV contrast enhanced MRE compared to diffusion-weighted MRE in children and young adults demonstrates that diffusion-weighted imaging in lieu of IV contrast administration provides comparable identification of both inflammatory wall thickening and lesion detection [30]. Another potential indication for MRE is surveillance of asymptomatic Crohn disease patients to assess subclinical disease activity. A study of 34 children and adolescents with asymptomatic Crohn disease patients undergoing MRE surveillance [52] found that several MRE imaging features (mural edema, hyperenhancement, engorged vasa recta, and restricted diffusion) were significant predictors of disease recurrence within 6 months, with sensitivity values of 71% to 86% and specificity values of 68% to 86%. Mural diffusion restriction was found to be the best predictor by multivariate regression and predicted future disease recurrence with an AUC of 0.786. MRE in this variant is also useful for stricture characterization. One study examined 31 bowel segments from pediatric Crohn disease patients who underwent surgical bowel resection and preoperative MRE [17]. Performance of MRE for fibrosis detection was relatively low accuracy (64.9%) because of mixed inflammation and fibrosis within strictures but was higher (83.3%) for fibrotic strictures without superimposed active inflammation.


Crohn Disease Child

Crohn Disease Child. Another study of 20 pediatric Crohn disease patients with symptomatic small bowel strictures and preoperative MRE [53] showed a significant histological correlation between fibrosis and inflammation (rho = 0.55) within strictures, as well as a significant association between small bowel dilation >3 cm on MRE and stricture fibrosis (odds ratio = 43). A study of 25 pediatric Crohn disease patients who underwent bowel stricture resection with preoperative MRE showed that texture analysis of the bowel wall signal intensities for detecting stricture fibrosis had a goodness-of- fit AUC value of 0.995 [54]. Radiography Abdomen Visualization of bowel pathology is limited on abdominal radiographs, which restricts use for disease surveillance or monitoring therapy. Crohn Disease-Child US Abdomen US abdomen can be used for imaging Crohn disease during therapy monitoring. US may be a particularly suitable alternative for younger children who would otherwise require sedation for MRE or CTE examinations [21]. Sonographic technique requires a systematic assessment of the entire bowel including terminal ileum, colon, and more proximal small bowel. All four quadrants of the abdomen should be evaluated in both the transverse and longitudinal planes [32]. Color Doppler US is also performed to facilitate mural hyperemia assessment. Sonographic features include abnormal bowel wall thickening (>3 mm in children), alteration of bowel wall signature, adjacent fatty proliferation, hyperemia, and engorgement of the vasa recta [32]. Patient features may adversely affect US including elevated body mass index as well as bowel gas resulting in shadowing. In the setting of pediatric Crohn disease though, obesity is less likely given that many patients have diminished nutrition [32]. The detection of alternative diagnoses is also decreased compared with CT or MRI. Literature supporting the use of US for grading disease activity is only partially developed.


Crohn Disease Child

Crohn Disease Child. In a meta-analysis, based on only three studies with 86 patients, it demonstrated an accuracy of only 44% [55]. A prospective pediatric study with subjects undergoing US before and after initiation of medical therapy with 29 patients and 231 US examinations was performed. US agreement was only moderate for involved length, bowel wall Doppler signal, and stricture; however, it was more substantial for maximum bowel wall thickness, penetrating disease, and abscess [56]. These authors did question US accuracy and reproducibility for assessment of medical therapy. US Abdomen With IV Contrast CEUS assesses microbubble enhancement pattern predominately of the bowel wall. Multiple CEUS agents are available, all with strong safety profiles. Following IV administration of these microbubbles, high-frequency sonographic waves cause oscillation of the microbubble core gas resulting in pronounced conspicuity. Quantitative features, such as time to peak enhancement, maximum enhancement, and areas under the enhancement curve, may be determined to supplement analysis. Studies in adult populations found that quantitative analysis facilitated differentiation of inflammatory from fibrostenotic strictures [39] and that both increased maximum peak intensity and wash in slope coefficient was indicative of active disease [40]. A meta-analysis of CEUS based on 8 studies with 428 adult patients indicated a sensitivity of 93%, a specificity of 87%, and an AUC of 0.96 [41]. A different meta-analysis of CEUS of 8 articles with a total of 332 adult patients indicated a pooled sensitivity of 94% and a specificity of 79% [42]. Also, there is a paucity of literature that reveals added benefit beyond US without IV contrast. One adult study, however, did show that quantitative CEUS parameters integrated with grayscale US with color Doppler imaging reduced indeterminate results [43]. Currently, there is a paucity of studies using CEUS in children.


Crohn Disease Child

Crohn Disease Child. CEUS will be an area of future development for children with Crohn disease and is currently being used clinically by several committee members to supplement US abdomen (without IV contrast) for monitoring and surveillance imaging. In this setting, CEUS is most useful in Crohn disease patients with a single segment of bowel involvement that is sonographically visible. Another avenue of potential future development that may supplement CEUS is determining the role to US shear wave elastography in pediatric patients, as literature is starting to emerge in adults [44]. WBC Scan Whole Body Tc-99m HMPAO WBC scan studies show sensitivities from 75% to 94% and specificities from 92% to 99% for intestinal inflammation in children [45]. More recently, Chroustova et al [46] found a sensitivity of 89% and a specificity of 91% in 85 children. Although the diagnostic parameters of a WBC scan whole body are useful for both diagnosis and disease activity assessment, significant practical limitations exist. One disadvantage is the Crohn Disease-Child decreased ability to detect and evaluate alternative diagnoses. Other significant disadvantages are the technical aspects including volume of blood required for labeling, longer acquisition times, and significantly limited usage for initial diagnosis. Variant 4: Child. Known Crohn disease, perianal fistula. Initial imaging. Perianal Crohn disease manifesting as either a fistula or an abscess is common, with 15% to 25% of patients exhibiting perianal Crohn disease in childhood and 38% during their lifetime [5,6]. Although examination under anesthesia by a pediatric surgeon has been a standard of care for assessment, advancements in imaging complement the clinical assessment. Imaging may also supplant examination under anesthesia in circumstances when noninvasive diagnostic information is sought, such as preprocedural planning or assessment of therapy response [2].


Crohn Disease Child

Crohn Disease Child. CT Pelvis If present, perianal disease may be identified within the field of view during acquisition if CTE is used for diagnosis, acute exacerbation, or therapy response. There is, however, insufficient literature to support primary imaging of perianal disease by pelvic CT. Fluoroscopy Contrast Enema Fluoroscopy contrast enema is uncommonly used in current practice. There is insufficient pediatric literature to support routine use for perianal Crohn disease. MRI Pelvis Because of the superior soft-tissue resolution allowing anatomic localization of penetrating disease in relation to the sphincteric musculature and perianal soft tissues, MRI pelvis with IV contrast is the study of choice for assessing perianal Crohn disease [5,6]. MRI of the pelvis in this setting is primarily acquired with higher-resolution T2- weighted fat-suppressed sequences and postgadolinium T1-weighted fat-suppressed images. Imaging in the axial and coronal planes may be obliqued to the anal canal depending upon institutional preference. Diagnostic performance of MRI pelvis with gadolinium may be as high as 81% sensitive and 100% specific in children [5]. Also, an adult meta-analysis of four studies showed MRI sensitivity and specificity for fistula detection were 87% and 69%, respectively, with greater specificity than US at 43% [57]. With standard pediatric MRE, which included this region, the sensitivity and specificity were 82% and 100% for perianal disease [58]. Unlike MRE, however, for MRI pelvis in this variant, oral contrast material is not necessary. There is little literature to specifically support pelvic MRI without IV contrast for perianal Crohn disease. However, noncontrast MRI will likely still yield diagnostic information for monitoring therapy response, whereas optimal anatomic distribution has previous been ascertained [6]. Pelvic MRI with contrast can also assist in predicting and monitoring treatment response.


Crohn Disease Child

Crohn Disease Child. A study of 36 children with perianal fistulizing Crohn disease study found that a maximum fistula length of <2.5 cm predicted treatment response, and a length >2.5 cm predicted disease progression [6]. Another pediatric study based on the Van Assche MRI scoring system demonstrated interval decrease in score following treatment compared with the baseline score at diagnosis (P = . 0170) [59]. Because of the superb soft-tissue resolution allowing determination of fistulous tracts and abscesses in relation to the anal sphincter musculature, as well as high diagnostic performance, MRI pelvis with administration of IV contrast in an integral part of care for perianal Crohn disease. US Pelvis Transperineal Transperineal US of the pelvis in children may serve as a useful alternative when perianal imaging is indicated, although anatomic delineation is more limited than MRI. US is an imaging option for perianal Crohn disease. Differing sonographic techniques have been described in adults and children including transcutaneous/transperineal approaches as well as endoanal US. Endoanal US is a technique used in adult patients with variable diagnostic accuracy and can be limited by luminal stenosis [2]. A meta-analysis of endoanal US based on four studies in adult patients showed a sensitivity of 87% and a specificity of 43%, with a specificity inferior to MRI [57]. There is insufficient literature to support endoanal US in children, and technical limitations such as smaller size and need for anesthesia preclude usefulness in pediatric patients. Other US techniques, however, are potentially more feasible in children. Transcutaneous perianal US was studied in 38 pediatric patients using MRI as the reference standard. Transcutaneous perianal US demonstrated a sensitivity, specificity, PPV, and negative predictive value of 76%, 53%, 84%, and 41% for fistulae and 56%, 98%, 90%, and 88%, respectively, for abscess compared with MRI [60]. An adult-focused meta-analysis of transperineal US from Crohn Disease-Child


Right Upper Quadrant Pain

Right Upper Quadrant Pain.  Introduction/Background Acute right upper quadrant pain is one of the most common presenting symptom in hospital emergency departments, as well as outpatient settings. Although gallstone-related acute cholecystitis (AC) is a leading consideration in diagnosis, a myriad of extrabiliary sources including hepatic, pancreatic, gastroduodenal, and musculoskeletal should also be considered. Cholelithiasis is a common entity and AC is a common manifestation of gallstone disease afflicting more than 20 million people in the United States and is the leading cause of inpatient admissions for gastrointestinal disease [6]. AC can be life-threatening; therefore, timely diagnosis is essential for proper treatment. However, most patients with AC experience right upper quadrant abdominal pain, nausea, vomiting, anorexia, and fever [7]. Information derived only from clinical history, physical examination, and routine laboratory tests has not yielded acceptable likelihood ratios sufficient to predict the presence or absence of AC. Also, this information does not yield sufficient diagnostic certainty for making management decisions. Therefore, imaging studies play a major role in establishing a diagnosis of AC and assessing possible alternate diagnoses if AC is not present [8]. Unless otherwise stated, the ratings and recommendations for this document specifically relate to the adult nonpregnant patient. OR aUniversity of Connecticut, Farmington, Connecticut. bJohns Hopkins Hospital, Baltimore, Maryland. cPanel Chair, Johns Hopkins University School of Medicine, Baltimore, Maryland. dPanel Vice-Chair, University of Alabama Medical Center, Birmingham, Alabama. eEmory University, Atlanta, Georgia; Committee on Emergency Radiology-GSER. fDuke University Medical Center, Durham, North Carolina. gUniversity of Texas Health Science Center at Houston and McGovern Medical School, Houston, Texas; American Gastroenterological Association. hOregon Health & Science University, Portland, Oregon.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. iDuke Signature Care, Durham, North Carolina; American College of Physicians. jUniversity of Alabama at Birmingham, Birmingham, Alabama, Primary care physician. kSchmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida; American College of Emergency Physicians. lOregon Health & Science University, Portland, Oregon; American College of Surgeons. mNorthShore University HealthSystem, Evanston, Illinois. nNew York University Langone Medical Center, New York, New York. oUniversity of Cincinnati Medical Center, Cincinnati, Ohio. pMcMaster University, Hamilton, Ontario, Canada; Commission on Nuclear Medicine and Molecular Imaging. qSpecialty Chair, Virginia Commonwealth University Medical Center, Richmond, Virginia. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org Right Upper Quadrant Pain Discussion of Procedures by Variant Variant 1: Right upper quadrant pain. Unknown etiology. Initial Imaging. In this clinical scenario, the patient presents with right upper quadrant pain and may have associated signs and symptoms. Although biliary disease is in the differential, it is not necessarily the leading consideration from the clinical presentation, and many other etiologies remain possible diagnostic considerations. Imaging methods for initial evaluation in patients in this clinical variant should be able to detect or exclude biliary disease and these other alternate diagnoses. CT Abdomen CT scanners are the workhorse modality for the assessment of nonspecific abdominal pain. CT also has the advantage of assessment of complications related to AC, as well as diagnosis of extrabiliary sources of right upper quadrant pain.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. Unlike ultrasound (US), CT can also better visualize the gastrointestinal tract, including gastroduodenal abnormalities such as severe inflammation or perforation, colitis involving the hepatic flexure, and abnormalities of the adjacent osseous structures. Pancreatic masses and acute pancreatitis are similarly better evaluated. Contrast enhancement is an additional advantage that can aid in visualizing and characterizing enhancing hepatic, pancreatic, adrenal, and bowel lesions. CT without intravenous (IV) contrast can detect some features and complications of AC, such as gallbladder wall thickening, pericholecystic inflammation, gas formation, and hemorrhage. However, some important features that add confidence to the diagnosis such as wall enhancement and adjacent liver parenchymal hyperemia, one of the earlier findings in AC, cannot be detected without IV contrast [7]. CT without and with IV contrast is not often viewed as helpful in assessing patients admitted with right upper quadrant abdominal pain because the noncontrast portion does not add value and little additional information is gained by the routine addition of a noncontrast phase to a contrast-enhanced phase in this clinical setting [10]. CT with IV contrast is a useful tool for the assessment of hepatic pathology such as liver abscess (including the ones <5 mm) and metastatic disease. Furthermore, dual-phase contrast-enhanced CT can detect hemorrhage including active extravasation from liver tumors such as adenomas or hepatocellular carcinomas with accurate identification of the bleeding source. Similarly, severe inflammation of the gastroduodenal region, as well as of the pancreas, can be well detected and characterized on contrast-enhanced CT. If the clinical question only pertains to the presence or absence of bowel perforation, noncontrast CT alone may be enough for the assessment.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. MRI Abdomen with MRCP Abdominal MRI with MR cholangiopancreatography (MRCP) offers excellent soft tissue contrast, and visualization of the gallbladder, biliary tree, and structures outside of the biliary tree. The length of the examination and claustrophobia hinders this test as an initial modality for right upper quadrant pain. Patient motion artifact is another significant factor in claustrophobic, sick, and uncooperative patients. MRCP offers isolated visualization of the biliary tree and can assess for intraluminal biliary pathology including choledocholithiasis as a cause of biliary pain or an etiology for acute pancreatitis. Contrast-enhanced abdominal MRI can help characterize hepatic, pancreatic, adrenal, and renal lesions that are indeterminate on US and CT. MRI can be useful in cases in which findings on US and CT are equivocal. In such cases, MRI may better identify stones in the gallbladder neck or cystic duct, which are seen as filling defects on MRCP and T2-weighted images, and associated gallbladder wall abnormalities, including wall thickening and pericholecytic fluid [11]. MRCP provides excellent anatomic detail of the biliary tract and has a high sensitivity for detecting choledocholithiasis [12,13]. Right Upper Quadrant Pain Nuclear Medicine Scan Gallbladder Tc-99m cholescintigraphy also has both high sensitivity and specificity (96% and 90%, respectively) for the diagnosis of AC but is limited in use in clinical practice because of several factors [14]. This modality is limited to visualization of the biliary tract, and therefore, alternative extrabiliary causes of right upper quadrant pain will not be detected. Although cholescintigraphy has a higher sensitivity and specificity for the evaluation of AC, US remains the initial test of choice detailed below in the US section [15-17]. The use of cholescintigraphy should be limited to patients with a high suspicion of AC and obstructive biliary disease in the presence of an equivocal US.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. Radiography Abdomen Abdominal radiography is a commonly used first-line imaging modality for patients presenting with acute abdominal pain. Radiography has been shown to be of value for patients with suspected foreign body, bowel obstruction, and bowel perforation [18]. Several studies reported a high specificity of radiography in diagnosing small-bowel obstruction. However, it lacks the sensitivity and specificity of diagnosing other causes of abdominal pain [18-20]. A 2015 study showed that radiographs have lower sensitivity in detecting major abnormalities and supplemental imaging such as CT or US revealed major abnormalities in an additional 22% of patients whose radiographs were interpreted as normal [21]. Abdominal radiography has shown low utility in the diagnosis of common etiologies of abdominal pain, especially right upper quadrant pain including biliary and hepatic disease, acute pancreatitis, and peptic ulcer disease, and the findings can be noncontributory. Specifically, the inherent low soft tissue contrast of abdominal radiographs prevents diagnosis of typical right upper quadrant diseases including AC and hepatic pathologies. Gallstones, a common cause of biliary colic, are radiopaque in only 15% to 20% cases, and hence, the majority of the stones being radiolucent remain occult on radiography [22]. Several prospective studies [18,20,23] concluded that radiographs added only minimal value beyond clinical evaluation in the diagnostic workup of patients with acute abdominal pain. Few recent studies have analyzed the utility of abdominal radiographs for right upper quadrant pain specifically. Abdominal radiography has little utility as initial imaging for right upper quadrant abdominal pain with low sensitivity of 30% and has not been proven to be of value for expected other expected diagnoses, most importantly right upper quadrant pain [20,24]. US Abdomen US is the most useful modality for evaluation of right upper quadrant abdominal pain.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. It is very accurate in diagnosing or excluding gallstones, with a reported accuracy of 96% for the detection of gallstones [7], and helps differentiate cholelithiasis from gallbladder sludge, polyps, or masses. AC is the most common cause of right upper quadrant abdominal pain. However, assessment of more than one- third of patients initially suspected of having AC will result in an alternative diagnosis [16]. US is the most useful first-line imaging modality in evaluating AC, with the additional advantage of identifying alternate diagnosis of hepatic disease. The reported sensitivity and specificity of US range from 50% to 100% and from 33% to 100%, respectively, with summary estimates of 81% and 83%, respectively [25]. A 2019 study showed US sensitivity and specificity were 61.8% and 98.4%, respectively; the sensitivity of US reached 85.2% and 90% in patients with AC/biliary colic and urolithiasis, respectively [26]. US is also the most useful imaging modality for the diagnosis of biliary colic, with an accuracy of 90% for demonstrating cholelithiasis, which may develop into AC if untreated in up to 20% of patients [27]. Furthermore, choledocholithiasis can lead to biliary obstruction and subsequent cholangitis or acute pancreatitis, and US has a sensitivity of up to 91% in detecting stones within the common bile duct [28]. Liver abscess and metastatic disease may also cause right upper quadrant pain. Similarly, symptomatic hepatic masses causing bleeding or hemoperitoneum may also be easily picked up on US. US can also help identify renal pathology causing right upper quadrant pain with a sensitivity of 73% to 100% for the detection of hydronephrosis caused by renal obstruction with an overall improved sensitivity compared with radiography [27]. Adrenal pathology may also contribute to the list of causes of right upper quadrant pain. Adrenal hemorrhage can be easily identified as a mass without identifiable Doppler flow.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. Ninety-five percent of patients with AC have gallstones, but the sensitivity of CT for the detection of these stones is only approximately 75%. Calcium-containing stones tend to be well seen; however, cholesterol stones may be isoattenuating or hypoattenuating compared with the attenuation of bile, making their detection difficult [29]. Right Upper Quadrant Pain Variant 2: Right upper quadrant pain. Suspected biliary disease. Initial imaging. CT Abdomen Although it has not been advocated as a primary imaging examination for acute right upper quadrant pain, CT can confirm or refute the diagnosis of AC in equivocal cases based on US or scintigraphy, with a negative predictive value approaching 90% [30]. It is usually most appropriate to perform this examination after a US and/or cholescintigraphy. CT may reveal such complications as gangrene, gas formation, intraluminal hemorrhage, and perforation [15-17,30-35]. Furthermore, CT has been advocated as a useful modality in preoperative planning, with the absence of gallbladder wall enhancement or presence of a stone within the infundibulum associated with a higher rate of conversion from laparoscopic to open cholecystectomy. The CT findings in AC are similar to those encountered by US [7] with the exception of gallstones, which may not be detected by CT. Other potential findings include adjacent liver parenchymal hyperemia, which can only be assessed if IV contrast is administered. Abnormal gallbladder wall enhancement can be seen in more advanced cases, as well as if IV contrast is employed [7]. Of note, the sensitivity for the detection of gallstones on CT is only approximately 75% and is dependent on differing density of the stone relative to bile [7]. CT is usually preferred over MRI, largely because of its speed [30].


Right Upper Quadrant Pain

Right Upper Quadrant Pain. CT without IV contrast can detect some features and complications of AC, such as gallbladder wall thickening, pericholecystic inflammation, gas formation, and hemorrhage, although some important features, such as wall enhancement and adjacent liver parenchymal hyperemia, cannot be detected without IV contrast. Adjacent liver hyperemia is actually one of the earlier findings in AC and can be a very useful problem-solving tool [7]. CT without and with IV contrast is not often viewed as helpful in assessing patients admitted with right upper quadrant abdominal pain. Little additional information is gained by the routine addition of a noncontrast phase to a contrast-enhanced phase in this clinical setting, [10]. MRI Abdomen with MRCP The presence of AC can be further explored using abdominal MRI, which often includes the use of an IV gadolinium-based contrast agent in cases in which other imaging tests are equivocal [7]. Several studies have suggested that abdominal MRI is a reliable alternative and can be particularly helpful in the patient who is difficult to examine with US [36-38]. It can perform superiorly to US in cases of gallstones in the gallbladder neck, the cystic duct, or the common bile duct [7]. As with CT without IV contrast, noncontrast MRI will not be able to detect all the imaging features or potential complications of AC. However, noncontrast MRI with MRCP has excellent accuracy for the detection of biliary stone disease, and, therefore, a noncontrast MRI is generally preferred over a noncontrast CT. Nuclear Medicine Scan Gallbladder Despite providing information limited to the hepatobiliary tract, cholescintigraphy has been advocated as a useful modality in this setting. Specifically, gallbladder nonvisualization with delayed imaging or morphine-augmented cholescintigraphy is highly accurate for evaluating the presence or absence of AC.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. One study states that gallbladder ejection fraction <30% may be useful in predicting the severity of cholecystitis and is associated with a higher complication rate in the setting of laparoscopic cholecystectomy [39]. However, although cholescintigraphy has a higher sensitivity and specificity for the evaluation of AC, US remains the initial test of choice for imaging patients with right upper quadrant pain for a variety of reasons, including shorter study time, morphologic evaluation, confirmation of the presence or absence of gallstones, evaluation of intrahepatic and extrahepatic bile ducts, and identification or exclusion of alternative diagnoses [15-17,40]. US Abdomen US is the first choice of investigation for biliary symptoms or right upper quadrant abdominal pain. It is very accurate at diagnosing or excluding gallstones, with reported accuracy of 96% for the detection of gallstones [7], and may differentiate cholelithiasis from gallbladder sludge, polyps, or masses. The diagnosis of chronic cholecystitis is difficult on anatomic imaging. The gallbladder may appear contracted or distended, and pericholecystic fluid is usually absent. An initial study from 1981 defined the sonographic Murphy sign as focal tenderness corresponding to a sonographically localized gallbladder, which, along with stones, sludge, and gallbladder wall thickening, allowed for differentiating AC from gallstones alone and chronic cholecystitis with gallstones [40]. Unfortunately, the Right Upper Quadrant Pain sonographic Murphy sign has a relatively low specificity for AC [41], and its absence is unreliable as a negative predictor of AC if the patient has received pain medication before imaging. Since that initial study, many subsequent studies have been conducted to assess the accuracy of US and cholescintigraphy. A meta-analysis by Shea et al [42] reviewed 22 studies evaluating cholescintigraphy and 5 studies evaluating US published between 1978 and 1990.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. The authors concluded that cholescintigraphy demonstrated the best sensitivity of 97% (95% confidence interval [CI], 96%-98%) and specificity of 90% (95% CI, 86%-95%) in detecting AC, whereas US had a sensitivity of 88% (95% CI, 74%-100%) and a specificity of 80% (95% CI, 62%-98%). Other studies performed since then have shown similar findings. Although cholescintigraphy is recognized to have a higher sensitivity and specificity, US remains the initial imaging test of choice for imaging patients with suspected AC for a variety of reasons, including shorter study time, morphologic evaluation, confirmation of the presence or absence of gallstones, evaluation of intrahepatic and extrahepatic bile ducts, gallbladder wall edema, pericholecystic fluid, and identification or exclusion of alternative diagnoses [15-17,40]. However, the usefulness of US is limited in critically ill patients where gallbladder abnormalities are common in the absence of AC [22,43]. If complicated cholecystitis (emphysematous, hemorrhagic, gangrenous, or perforated, among others) is suspected, US remains the first choice of investigation for biliary symptoms or right upper quadrant abdominal pain. It is important to note, however, that some patients with complicated cholecystitis may present just like those with noncomplicated disease [7]. Depending on the complication, one may detect intraluminal hyperechoic blood products, intraluminal gas or gas in the gallbladder wall, intraluminal debris or membranes, or discontinuity of the gallbladder wall [7,30,44]. The gallbladder may appear contracted or distended, and pericholecystic fluid is variably present. Although its sensitivity to some complications of cholecystitis is often limited, a normal appearance of the gallbladder, especially the wall, makes acute gallbladder pathology very unlikely. Thus, US remains the first imaging choice if complications of cholecystitis are suspected. Variant 3: Right upper quadrant pain.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. No fever and no high white blood cell (WBC) count. Suspected biliary disease. Negative or equivocal ultrasound. Next imaging study. CT Abdomen CT is not the first-line imaging test for suspected biliary causes of right upper quadrant abdominal pain. However, if US is negative for AC and there is no alternative diagnosis, CT, preferably with IV contrast, is the next preferred imaging examination for identifying those additional causes of right upper quadrant abdominal pain. When a diagnosis of AC is not prospectively suspected, CT may also be used to demonstrate AC in patients who have nonspecific abdominal pain. CT may also be valuable for further clarification of sonographic findings. It is important to select the proper imaging protocol based on clinical information and other imaging. For example, evaluation for nephrolithiasis is best performed with a noncontrast-enhanced CT, whereas characterization of a liver lesion may be more accurate with a multiphasic CT or MRI, which may include precontrast and postcontrast images. Detection of gallstones on CT with IV contrast depends on differing density of the stone relative to bile. Reported sensitivity for gallstone detection by CT is approximately 75%. Calcified gallstones are readily apparent. Cholesterol stones may also be seen as less dense than bile. Nitrogen gas may collect within degenerating gallstones, creating central fissures that may also be seen as different attenuation from bile [7]. The diagnosis of chronic cholecystitis is difficult to make at imaging. Chronic cholecystitis is associated with gallstones in 95% of cases and may result from a single or multiple recurrent episodes of AC. Chronic inflammation causes the gallbladder to become thickened and fibrotic. On CT, there may be absence of adjacent liver parenchymal hyperemia and pericholecystic inflammatory change, with nonvisualization of gallstones [7].


Right Upper Quadrant Pain

Right Upper Quadrant Pain. Noncontrast abdominal CT has very limited value in the assessment of suspected biliary sources of right upper quadrant abdominal pain. Unenhanced abdominal CT may or may not demonstrate cholelithiasis, depending on the density of the stones. Pericholecystic inflammatory fat stranding may be seen in AC. Evaluation of biliary ductal dilatation is limited. CT without and with IV contrast is not often viewed as helpful in assessing patients admitted with right upper quadrant abdominal pain. Little additional information is gained by the routine addition of a noncontrast phase to a contrast-enhanced phase in this clinical setting [10]. Right Upper Quadrant Pain MRI Abdomen with MRCP MRCP is excellent for the detection of cholelithiasis/choledocholithiasis, with reported sensitivity of 85% to 100%, specificity of 90%, and accuracy of 89% to 90% [7]. MRCP is superior to US in the evaluation of cystic duct and common bile duct calculi and calculi impacted in the gallbladder neck. Visualization of the common bile duct and even the cystic duct is a significant advantage of MRI over US in the evaluation of right upper quadrant pain [38]. MRI may also demonstrate findings to help distinguish acute from chronic cholecystitis. In chronic cholecystitis, gallbladder wall thickening related to chronic inflammation shows low signal intensity, as opposed to AC, which is associated with edema and T2 signal hyperintensity. Abdominal MRI with IV contrast may show perihepatic contrast enhancement in the setting of acute inflammation, which is helpful for differentiating AC from chronic cholecystitis [7]. Although contrast-enhanced examinations are preferred, MRI of the abdomen without IV contrast is also useful. It often provides improved characterization of incidental sonographic liver findings as compared to noncontrast CT. Standard T2-weighted MRI generally allows visualization of both normal caliber and dilated bile ducts.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. Noncontrast MRI with MRCP is very helpful in the follow-up of known hepatobiliary stone disease. Abdominal MRI with, and sometimes without, IV contrast in combination with MRCP provides comprehensive evaluation of the hepatobiliary system. In addition to evaluating for cholelithiasis and choledocholithiasis, additional pathologies may be identified. Sources of biliary ductal dilatation, such as masses and lymph nodes, may be identified. Nuclear Medicine Scan Gallbladder Low-grade, partial, or intermittent biliary obstruction may present with symptoms of recurrent right upper quadrant abdominal pain, mimicking chronic cholecystitis and numerous nonbiliary causes of abdominal pain. Nuclear medicine hepatobiliary imaging also aids in the diagnosis of partial biliary obstruction that is due to stones, biliary stricture, and sphincter of Oddi obstruction. Sphincter of Oddi evaluation with cholecystokinin cholescintigraphy does not carry the risk of pancreatitis, which may be seen with manometric evaluation. The use of cholecystokinin- augmented nuclear medicine hepatobiliary imaging in patients with pain of biliary origin is an acceptable practice under current Society of Gastrointestinal and Laparoendoscopic Surgeons clinical guidelines [45]. Nuclear medicine hepatobiliary imaging with calculation of the gallbladder ejection fraction after cholecystokinin infusion may be used to diagnose chronic gallbladder disease, partial biliary obstruction, and biliary dyskinesia as a cause of right upper quadrant pain. However, this test may be less useful in patients with atypical symptoms. Variant 4: Right upper quadrant pain. Fever, elevated WBC count. Suspected biliary disease. Negative or equivocal ultrasound. Next imaging study.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. CT Abdomen Although it has not been advocated as a primary imaging examination for acute right upper quadrant pain, CT with IV contrast can confirm or refute the diagnosis of AC in equivocal cases based on US or scintigraphy, with a negative predictive value approaching 90% [30]. CT may reveal such complications as gangrene, gas formation, intraluminal hemorrhage, and perforation [15-17,30-35]. Furthermore, CT has been advocated as a useful modality in preoperative planning, with the absence of gallbladder wall enhancement or presence of a stone within the infundibulum associated with conversion from laparoscopic to open cholecystectomy. Prior knowledge of these imaging findings may help guide appropriate surgical approach [46]. Clinical conditions that can mimic AC, in terms of presentation with acute right upper quadrant pain, include chronic cholecystitis, peptic ulcer, pancreatitis, gastroenteritis, ascending cholangitis, and bowel obstruction, among others. However, AC is a fairly common disease that presents with right upper quadrant pain and is often the initial diagnosis to exclude. If US or scintigraphy are negative for AC and there is no alternative diagnosis, CT, preferably with IV contrast, is the next preferred imaging examination for identifying those disorders. When a diagnosis of AC is not prospectively suspected, CT may also be used to demonstrate AC in patients who have nonspecific abdominal pain. The CT findings in AC are similar to those encountered by US [7] with the exception of gallstones, which may not be seen with CT. Other potential findings include adjacent liver parenchymal hyperemia, which cannot be detected without IV contrast. Abnormal gallbladder wall enhancement can be seen in more advanced cases [7]. Right Upper Quadrant Pain


Right Upper Quadrant Pain

Right Upper Quadrant Pain. CT without IV contrast can detect some features and complications of AC, such as gallbladder wall thickening, pericholecystic inflammation, gas formation, and hemorrhage, although some important features, such as wall enhancement and adjacent liver parenchymal hyperemia, cannot be detected without IV contrast. Adjacent liver hyperemia is actually one of the earlier findings in AC and can be a very useful problem-solving tool [7]. CT without and with IV contrast is not often viewed as helpful in assessing patients admitted with right upper quadrant abdominal pain. Little additional information is gained by the routine addition of a noncontrast phase to a contrast-enhanced phase in this clinical setting [10]. MRI Abdomen with MRCP The presence of AC can be further explored using abdominal MRI, which often includes the use of an IV gadolinium-based contrast agent, in cases in which other imaging tests are equivocal [7]. As with CT, MRI is not advocated as a primary imaging examination to evaluate acute right upper quadrant pain; however, several studies have suggested that abdominal MRI is a reliable alternative and can be particularly helpful in the patient who is difficult to examine with US [36-38]. Although factors such as longer acquisition times limit its use in the emergency setting, more consistent visualization of the extrahepatic biliary tree is an important advantage of its use [47,48]. MRI is considered the best modality for evaluating hepatic and biliary abnormalities that are not characterized by US. It can perform superiorly to US in cases of gallstones in the gallbladder neck, the cystic duct, or the common bile duct [7]. Few studies have examined the role of MRI in evaluating AC. MRI sensitivity estimates range from 50% to 91%, with specificity ranging from 79% to 89%. According to the meta-analysis by Kiewiet et al, the summary sensitivity is 85% (95% CI, 66%-95%) and the specificity is 81% (95% CI, 69%-90%) [25,38,47,48], similar to those of US.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. A study by Byott and Harris [49] advocated for the use of limited MRI (rapid acquisition half-Fourier acquisition single shot turbo spin echo [HASTE] coronal and axial sequences, without IV contrast) for evaluation of AC, especially in younger patients. As with CT without IV contrast, noncontrast MRI will not be able to detect all the imaging features or potential complications of AC. However, noncontrast MRI with MRCP has excellent accuracy for visualization of normal and dilated bile ducts and the detection of stone disease compared to noncontrast CT. Standard T2-weighted imaging can better demonstrate gallbladder wall edema and pericholecystic fluid than noncontrast CT. Variant 5: Right upper quadrant pain. Suspected acalculous cholecystitis. Negative or equivocal ultrasound. Next imaging study. CT Abdomen Patients with suspected acalculous cholecystitis are typically critically ill, and CT has a role in evaluating these patients [31]; however, as with US, the frequent prevalence of nonspecific abnormal imaging findings in the gallbladders of critically ill patients limit its diagnostic value. Nevertheless, when the gallbladder appears completely normal on CT, there is a low probability of any surgical finding in the gallbladder [50]. CT without IV contrast can detect some features and complications of acalculous cholecystitis, such as gallbladder wall thickening, pericholecystic inflammation, gas formation, and hemorrhage. However, some important features, such as wall enhancement and adjacent liver parenchymal hyperemia, cannot be detected on noncontrast CT and so IV contrast is preferred. Adjacent liver hyperemia is actually one of the earlier findings in acalculous cholecystitis and can be a very useful problem-solving tool [7]. Right Upper Quadrant Pain CT without and with IV contrast is not often viewed as helpful in assessing patients admitted with right upper quadrant abdominal pain.


Right Upper Quadrant Pain

Right Upper Quadrant Pain. Little additional information is gained by the routine addition of a noncontrast phase to a contrast-enhanced phase in this clinical setting [10]. MRI Abdomen with MRCP MRI has not been evaluated sufficiently in acalculous cholecystitis and is often impractical, given patient comorbidity. Therefore, its usefulness in the setting of suspected acalculous cholecystitis is limited. However, MRI may play a role in cases where other imaging tests are equivocal [7]. Several studies have suggested that abdominal MRI is a reliable alternative and can be particularly helpful in the patient who is difficult to examine with US [36- 38]. MRI can be the next best imaging modality when acalculous cholecystitis is excluded, and MRI with MRCP is considered the best modality for evaluating hepatic and biliary abnormalities that are not characterized by US. It can perform superiorly to US in cases of gallstones in the gallbladder neck, the cystic duct, or the common bile duct [7]. Nuclear Medicine Scan Gallbladder Cholescintigraphy is a very sensitive diagnostic test because most cases of acalculous cholecystitis are associated with cystic duct obstruction, similar to the calculous form of the disease. Some cases of acalculous cholecystitis, however, are related to direct inflammation of the gallbladder, leading to false-negative studies when using cholescintigraphy [51]. It should also be noted that the specificity of cholescintigraphy may be limited in the critically ill patient where nonvisualization of the gallbladder may occur in the absence of inflammation despite preimaging cholecystokinin administration. However, cholescintigraphy remains the imaging examination of choice when acalculous cholecystitis is suspected. Image-Guided Biopsy Liver Percutaneous cholecystostomy can be both diagnostic and therapeutic, and it is usually considered safe in hospitalized patients suspected of having acalculous cholecystitis [52,53].


Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm.  aStanford University Medical Center, Stanford, California. bResearch Author, Stanford University Medical Center, Stanford, California. cPanel Chair, University of Vermont Medical Center, Burlington, Vermont. dPanel Vice-Chair, University of Michigan, Ann Arbor, Michigan. eUniversity of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; Society for Cardiovascular Magnetic Resonance. fKnight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Society of Cardiovascular Computed Tomography. gBoston Medical Center/Boston University School of Medicine, Boston, Massachusetts. hUniversity of Alabama at Birmingham, Birmingham, Alabama. iNew York University Langone Health, New York, New York; Society for Cardiovascular Magnetic Resonance. jQueen's University, Kingston, Ontario, Canada; American Society of Echocardiography. kNorthShore University HealthSystem, Evanston, Illinois. lNorthern Ontario School of Medicine, Sudbury, Ontario, Canada; American College of Emergency Physicians. mYale School of Medicine, New Haven, Connecticut; American Society of Nuclear Cardiology. nHarvard Medical School and Beth Israel Deaconess Medical Center, Boston, Massachusetts; Society for Vascular Surgery. oBoston Medical Centers, Boston University, and Chobanian and Avedisian School of Medicine, Boston, Massachusetts; Society for Vascular Surgery. pIndiana University School of Medicine and Indiana University Health, Indianapolis, Indiana; Committee on Emergency Radiology-GSER. qMassachusetts General Hospital, Boston, Massachusetts. rUT Southwestern Medical Center, Dallas, Texas. sDuke University Medical Center, Durham, North Carolina, Primary care physician. tSpecialty Chair, Brigham & Women's Hospital, Boston, Massachusetts. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels.


Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org All elements are essential: 1) timing, 2) reconstructions/reformats, and 3) 3-D renderings. Standard CTs with contrast also include timing issues and reconstructions/reformats. Only in CTA, however, is 3-D rendering a required element. This corresponds to the definitions that the CMS has applied to the Current Procedural Terminology codes. OR Discussion of Procedures by Variant Variant 1: Pulsatile abdominal mass, suspected abdominal aortic aneurysm. Initial imaging. Aortography Abdomen Although AAAs can be diagnosed by catheter-based aortography of the abdominal aorta, it is invasive and has low sensitivity [3,7]. The width of the contrast column on aortography may underestimate the true aortic diameter if there is significant mural thrombus obscuring the luminal contour of the aneurysm or if the 2-D image acquisition plane is not orthogonal to the plane of maximum aortic diameter. Aortography is the main diagnostic component of endovascular AAA interventions and may be particularly useful in emergent cases of ruptured AAA. CT Abdomen and Pelvis CT abdomen and pelvis with intravenous (IV) contrast, CT abdomen and pelvis without and with IV contrast, and CT abdomen and pelvis without IV contrast are noninvasive, fast, and commonly used to evaluate various abdominopelvic pathologies, including aortic and nonaortic causes of a pulsatile abdominal mass. There is no specific literature regarding aortic measurements on standard CT images, with or without IV contrast, for the initial imaging evaluation of suspected AAA; however, aortic diameters can be accurately assessed on CT images if the abdominal aortic contour is well visualized and can be distinguished from adjacent structures.


Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm. AAAs can be incidentally diagnosed on both contrast- and noncontrast-enhanced CT scans performed for various other clinical indications [4,5,21-23]. In determining maximum aortic diameter on CT, the OTO aortic diameter perpendicular to the long axis of the aorta is recommended [7]. This is obligatory for noncontrast CT images in which the aortic wall and lumen cannot be distinguished. Noncontrast CT has been found to be more sensitive than ultrasound (US) in identifying AAAs [24]. CTA Abdomen and Pelvis CTA abdomen and pelvis with IV contrast and CTA abdomen and pelvis without and with IV contrast provide rapid image acquisition of submillimeter, isotropic, 3-D data sets of the aorta and its branch vessels with high spatial resolution [25-27]. Measurement of the maximal aortic diameter based on the OTO wall diameter perpendicular to the long axis of the aorta on CTA is considered the reference standard for AAA diagnosis and management decision making [7]. CTA is also the imaging procedure of choice for preoperative assessment before endovascular or open surgical repair [10,13,26,28]. The scan range should include the iliofemoral arteries to evaluate the access vessels and also the chest in patients with thoracoabdominal AAA. Pulsatile Abdominal Mass CT, preferably CTA, is recommended for evaluation of symptomatic patients who present with acute onset abdominal or back pain, particularly in the presence of a pulsatile abdominal mass or significant risk factors for AAA [7]. Whether CTA should be the initial imaging modality used for evaluation of asymptomatic patients suspected to have an AAA is less clear. Dual-energy CTA, which allows for simultaneous acquisition of CT data with 2 different photon energy spectra, can be used to characterize AAAs with reduced IV iodinated contrast dose without compromising imaging quality [29,30].


Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature supporting the use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT for initial imaging evaluation of suspected AAA. The CT component of PET/CT can be used for the incidental diagnosis of AAA. FDG-PET/CT can play a role in the diagnosis of inflammatory and mycotic aortic aneurysms [10,31,32] and in predicting risk for AAA rupture [33]. MRA Abdomen and Pelvis MR angiography (MRA) abdomen and pelvis with IV contrast and MRA abdomen and pelvis without and with IV contrast are alternatives to CTA for the diagnosis and preintervention evaluation of AAAs [8,10,13,25,27,28]. Limitations of MRA and MRI in general include longer imaging acquisition times and limited ability to characterize aortic wall calcifications. MRA abdomen and pelvis without IV contrast can also be used for evaluation of suspected AAA. MRA can be performed without gadolinium-based contrast agents (GBCAs) using techniques such as time-of-flight, balanced steady-state free precession, phase-contrast, and quiescent-interval single-shot imaging [34]. Disadvantages of noncontrast-enhanced MRA include longer image acquisition times and increased motion artifacts [34]. Contrast- enhanced MRA is used more commonly than noncontrast-enhanced MRA for imaging evaluation of AAAs. Ferumoxytol, an ultrasmall superparamagnetic iron oxide particle, is an emerging alternative to GBCAs for contrast-enhanced MRA [35,36]. Ferumoxytol was originally designed as a blood pool contrast agent for MRI and has a longer duration of intravascular signal than GBCAs. Although the latest recommendations from the International Society for Magnetic Resonance in Medicine are for measurement of ITI aortic wall diameter on double-oblique reformatted images perpendicular to the vessel long- axis for measurement technique, the OTO aortic wall diameter should also be reported in cases of aneurysm or wall thickening if that approach is adopted [37].


Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm. The ITI wall measurement method was recommended because of its high conformity to the LTL measurements used in echocardiography, which is a consideration more relevant to the thoracic aorta [25,37]. The Society for Cardiovascular Magnetic Resonance and others advocate measurement of the outer aortic wall contour for aneurysms [38,39]. MRI Abdomen and Pelvis For the initial imaging evaluation of suspected AAA, the considerations for MRI of the abdomen and pelvis without dedicated MRA sequences are similar to that of MRA [8,10,25]. As with CT, a routine MRI abdomen and pelvis with IV contrast or MRI abdomen and pelvis without and with IV contrast can be used to measure abdominal aortic diameter if the aortic contour is well depicted. Either procedure may also characterize possible nonaortic causes of a pulsatile abdominal mass. AAAs can also be incidentally detected on MRI of the abdomen and pelvis performed for other reasons [5]. Accurate and reproducible aortic diameter measurements, comparable to CTA measurements, can be obtained from MRI without IV contrast by using black-blood sequences acquired with spin-echo techniques [40]. With advanced imaging methods, MRI can also provide functional and hemodynamic data, such as quantification of aortic wall stiffness and blood flow [25]. Radiography Abdomen and Pelvis There is no relevant literature supporting the use of radiography for the initial imaging evaluation of a pulsatile abdominal mass suspected to be an AAA. Radiography is not recommended for initial imaging for suspected AAA because of its low sensitivity for AAA detection [3,7]. AAA can be incidentally discovered on abdominal radiographs obtained for other purposes if aortic wall calcifications are visible and allow for assessment of aortic diameter; however, AAA morphology and extent may not be accurately or fully evaluated [3]. Pulsatile Abdominal Mass


Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm. US Aorta Abdomen Transabdominal US of the abdominal aorta poses negligible risk to patients and can reliably detect the presence of an AAA in nearly all patients with sensitivity and specificity approaching 100% [3,9,10,16]. With the portability of US machines, sonographic evaluation of the abdominal aorta can be performed in a wide range of settings, including in the emergency department [16,41]. US of the abdominal aorta is the mainstay imaging procedure for AAA screening and surveillance [7,12,16,42,43] and is often the first-line imaging study performed for evaluation of asymptomatic patients suspected to have an AAA [9,10,16,44]. In 1% to 2% of cases, the abdominal aorta cannot be adequately evaluated by US because of large patient body habitus or excessive overlying bowel gas [14,45]. Pre-evaluation overnight fasting is recommended to reduce bowel gas in patients [3,10,16]. Compared to CT, US underestimates AAA diameters by an average of 1 to 3 mm [15,16,54-56]. For preintervention planning for AAA endovascular or surgical repair, US is insufficiently precise and does not provide imaging information on access vessels and abdominal aortic branches [7,13]. A CTA, or alternatively MRA, is needed when the size threshold for repair is reached [10,13,44]. To overcome variations in imaging plane orientation that can occur with conventional 2-D US, 3-D US has shown promise for improved accuracy and reproducibility in aortic diameter measurements by allowing for measurements to be made in the plane orthogonal to the centerline of the abdominal aorta [57,58]. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www. acr.org/ac.


Pretreatment Staging of Urothelial Cancer.  Introduction/Background The American Cancer Society estimates that in 2023, there will be 82,290 new cases of bladder cancer and 16,710 deaths from the disease in the United States [1]. Bladder cancer has a high tendency toward multifocality at presentation and recurrence after treatment [2]. Urothelial carcinoma (UC) (previously known as transitional cell carcinoma) of the bladder is overwhelmingly the most common histologic type of bladder cancer in industrialized nations, accounting for >90% of all cases [3]. The median age of patients at diagnosis with bladder cancer in the United States is 73 years. Almost 85% of patients with bladder cancer present with hematuria, which is either gross or microscopic and is usually painless and intermittent [4]. UC is a very common tumor, quoted as overall the sixth most common tumor (fourth in male individuals), with the majority of cases arising in the bladder. Primary lesions arising in the upper tract are relatively uncommon at approximately 5% to 10% [1]. The hallmark of UC is multiplicity and recurrence, with nearly 2% to 4% of patients with bladder cancer developing upper tract UC (UTUC). In addition, 40% of patients with UTUC develop UC of the bladder [5]. UTUC has often been grouped with other renal cancers in the literature, making the true incidence of UTUC difficult to evaluate. Pelvicalyceal location is twice as common for UTUC as ureteral location, with estimates suggesting that approximately 15% of renal tumors are actually UC [5]. The incidence of UTUC has been increasing recently, which may be related to overall improved survival of patients with UC of the bladder and the associated risk of developing metachronous UTUC in those patients [5]. UC of the bladder spreads by local extension from the urothelium, through the lamina propria, into the muscularis propria or detrusor muscle layer, then to the perivesical fat.


Pretreatment Staging of Urothelial Cancer. It has been estimated that 70% to 85% of UC of the bladder is nonmuscle invasive at presentation [3]. Invasion of the muscularis propria and beyond, termed muscle- invasive bladder cancer (MIBC), increases the risk for more distant spread. The most common metastatic sites for MIBC include lymph nodes, bone, lung, liver, and peritoneum [6]. UTUC disseminate via lymphatic and hematogenous spread as well as direct extension. The most common sites of metastases for UTUC are lungs, liver, bones, and lymph nodes. A greater proportion of UTUCs are invasive at diagnosis, compared with UC of the bladder, at approximately two- thirds, and multifocal disease has been reported in approximately 25% to 30% of UTUCs at the time of diagnosis [7,8]. UTUC is approximately twice as common in men than women [5] compared with bladder cancer, which is 4 times as common in men. Presenting complaint in 75% to 95% of patients with UTUC is hematuria. Risk factors for developing UC of the bladder and UTUC are similar, contributing to the field exposure principle. Bladder lymph node mapping has demonstrated the complexity and extent of bladder lymphatic drainage. Drainage extends beyond the external iliac vessels and obturator fossa, included in a limited pelvic nodal dissection, to also involve the internal iliac and common iliac vessels up to the uretero-iliac crossing and occasionally extending to the inferior mesenteric artery [9]. Traditionally, lymph nodes have been considered suspicious based on increased size, however, newer MRI techniques and fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT can improve malignancy detection in subcentimeter-sized nodes [10-12]. Reprint requests to: publications@acr.org Pretreatment Staging of Urothelial Cancer UC is staged by its extent at presentation and graded as either low grade or high grade.


Pretreatment Staging of Urothelial Cancer. The standard staging system is the Tumor, Node, Metastasis (TNM) system, which encompasses the status of the primary tumor (T), lymph nodes (N), and metastases (M). The eighth edition of the American Joint Committee on Cancer Staging Manual is still currently applicable for TNM staging of UCs [13]. Radical cystectomy with pelvic lymphadenectomy remains the reference standard treatment for MIBC [14]. Neoadjuvant cisplatin-based combination chemotherapy is increasingly being used in these patients and has been shown to improve disease-specific and overall survival compared with surgery alone [15,16]. Alternatively, bladder preservation with concurrent chemoradiotherapy and maximal transurethral resection of bladder tumor (TURBT) is also now included as a category 1 recommendation for localized MIBC in National Comprehensive Cancer Network guidelines [17]. Moving forward, immune-checkpoint inhibitors and molecular-profiling technologies hold the potential to fundamentally change management of bladder cancer [18]. For patients with UTUC with nonmetastatic disease and a normal contralateral kidney, traditionally, standard treatment was an open radical nephroureterectomy with bladder cuff excision. More recent systemic evidence review shows equivalent oncologic outcomes for open and minimally invasive (laparoscopic, hand-assisted laparoscopic, robot-assisted laparoscopic) approaches [8,19]. In a subset of carefully selected patients, less invasive approaches such as kidney sparing surgery or ablation may be suitable alternatives [8,20]. The principal task of imaging is to characterize the site of known UC in addition to evaluating for additional secondary sites in the ureters or bladder, extravesical/ureteral spread, and nodal and distant metastases [21]. Many patients may have already had imaging during the workup of hematuria. Some local practice patterns do not routinely administer intravenous (IV) contrast to renal transplant patients.