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Imaging in the Evaluation of the Young Patient With Inflammatory Bowel Disease: What the Gastroenterologist Needs to Know

Anupindi, Sudha A.*; Grossman, Andrew B.; Nimkin, Katherine; Mamula, Petar; Gee, Michael S.

Journal of Pediatric Gastroenterology and Nutrition: October 2014 - Volume 59 - Issue 4 - p 429–439
doi: 10.1097/MPG.0000000000000475
Invited Review
Free

ABSTRACT Imaging plays a pivotal role in the diagnosis and management of children and young adults with inflammatory bowel disease. The clinician is presented with numerous imaging options, and it can be challenging to decide which test is the best option. In this article we review the present imaging techniques available in the evaluation of inflammatory bowel disease, with emphasis on the advantages, disadvantages, and radiation burden of each test. Finally, we highlight a few common clinical scenarios and propose an imaging algorithm to approach these diagnostic challenges.

*Department of Radiology

Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA

Department of Radiology, Division of Pediatric Imaging, Massachusetts General Hospital, Boston.

Address correspondence and reprint requests to Sudha A. Anupindi, MD, Department of Radiology, Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, 34 St & Civic Center Blvd, Philadelphia, PA 19104 (e-mail: anupindi@email.chop.edu).

Received 20 October, 2013

Accepted 19 June, 2014

The authors report no conflicts of interest.

Inflammatory bowel disease (IBD) is a chronic illness that affects children and young adults throughout their lives. Lifelong waxing and waning exacerbation of disease is the hallmark of IBD. Imaging is crucial for diagnosis, evaluation, and management of complications and understanding disease progression and remissions. Advances in imaging technology have led to an ever increasing number of imaging options for the clinician. It is often difficult to choose among the variety of imaging modalities that are available to evaluate these patients.

Imaging studies must be chosen based on the clinical question; considerations include the child's age, need for sedation, comfort level, expense, and length of examination. Presently, the most common modalities used in the evaluation of children with IBD include barium small bowel studies, computed tomography (CT), and magnetic resonance enterography (MRE). Occasionally, enteroclysis is used in challenging cases. Ultrasound (US), commonly used outside of North America, is emerging as a useful modality in both diagnosis and follow-up of disease and complications. Nuclear medicine examinations, such as tagged white blood cell scans and positron emission tomography-CT, are not routinely performed and have gone out of favor because other modalities have provided more comprehensive information regarding anatomy and function. In general, nuclear medicine studies have inferior spatial resolution (white blood cell scans) and radiation exposure (positron emission tomography-CT) prohibitive of routine use. When choosing an imaging modality it is important to consider the radiation burden to the patient, especially when repeated imaging is required during the course of treatment and management.

This article provides the present imaging choices available to the gastroenterologist, describes these techniques concisely with attention to radiation dose risks when applicable, and enumerates the practical imaging algorithms for common clinical scenarios.

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CURRENT IMAGING EXAMINATIONS

Fluoroscopic Barium Small Bowel Follow-Through Studies

Fluoroscopic barium small bowel follow-through (SBFT) is still commonly used in the initial diagnosis and evaluation of children with potential IBD despite the advent of more sophisticated imaging modalities such as CT and MRE. Despite its low sensitivity and specificity and use of ionizing radiation, SBFT examinations are widely available, easy to perform, do not require sedation, and can be done in all age groups safely at a lower cost than a CT enterography (CTE) or MRE. For these reasons it is still favored by many pediatric gastroenterologists. The study is typically performed in the mornings, and patients are required to fast (nothing by mouth, NPO) for at least 4 to 6 hours before the study, depending on the age of the child. Flavored barium (barium sulfate suspension 96% w/w; E-Z-EM Inc, Lake Success, NY) is given to the patient orally, and immediate and delayed films, in half-hour intervals, are taken of the upper gastrointestinal (UGI) tract and small bowel. The UGI study provides anatomic detail, rather than mucosal detail, which is better seen with endoscopy, of the esophagus, stomach, duodenum, and proximal jejunum to the level of the ligament of Treitz. The SBFT assesses the entire small bowel beyond the ligament of Treitz to the terminal ileum, but does not evaluate the colon. The termination point of the study is when the contrast fills the terminal ileum and cecum. Typically, the entire study takes between 1 and 3 hours and is dependent on the bowel transit time. The examination may take several hours, especially in patients with extensive small bowel disease, resulting in a delayed transit and/or stricture or obstruction. Crohn disease (CD) is the major pediatric indication for SBFT, and the common pathological and functional features seen at imaging include bowel wall thickening with irregularity and ulcerations, cobblestoning, luminal narrowing, separation of bowel loops, decreased peristalsis, and, in some cases, fistulas (Fig. 1).

FIGURE 1

FIGURE 1

Published pediatric reports of the diagnostic capability of SBFT in children are few, and the data are based on detection of terminal ileal disease compared with ileoscopy and comparing SBFT with modalities such as CT or MRE (1–4). Overall, the sensitivity ranges from 45% to 76% with a specificity of 67% to 96% (3–5). The low sensitivity of the barium study is attributed to poor distention and opacification of the bowel loops and substantial intra- and interobserver variations in interpretations (6). Of note, 2 other important limitations of the barium SBFT are the exposure to ionizing radiation and the lack of evaluation of extramural abnormalities. Because of all of these limitations of SBFT examinations, CT and MR are more appealing (Table 1).

TABLE 1

TABLE 1

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CT and CTE

CT has become the primary imaging modality for evaluating IBD and its complications in the United States for the last 15 years in adults, owing to a combination of rapid scan time, high-resolution evaluation of intestinal and extraintestinal disease manifestations, and 24-hour availability in most hospitals (7). In some centers CT may also be the first line of imaging in children with IBD, serving as a baseline examination, whereas MRE or US are performed as follow-up imaging studies to minimize patient cumulative ionizing radiation dose (7). The development of helical multidetector row CT scanners allows high spatial resolution imaging of the entire abdomen and pelvis in just a few seconds, generating isotropic images that can be reconstructed in all 3 dimensions to facilitate visualization of subtle abnormalities. CT scans are typically performed for IBD evaluation following administration of both oral and intravenous (IV) contrast to detect bowel wall abnormalities and abnormal enhancement. Patients are kept NPO for several hours before the study. Conventional CT uses positive enteral contrast agents, usually barium-containing solutions, which increase the attenuation of the bowel lumen and conspicuity of bowel wall abnormalities and extraluminal fluid collections. Positive enteric contrast can, however, obscure IV-contrast enhancement of the bowel wall. Additionally, positive oral contrast agents opacify but do not always distend the bowel well.

A dedicated CTE technique was developed that is specifically tailored to detect small bowel inflammation and uses neutral density enteral contrast agents that distend but do not opacify the bowel lumen (8). Such agents, which are typically commercially available preparations that are isodense to water but nonabsorbable, have improved accuracy for detecting mural hyperenhancement as well as areas of nondistensibility, such as strictures (8). The patient consumes a large volume (>1 L in an adult, and 450–1350 mL in pediatric patients, depending upon weight) of enteral contrast for 45 to 60 minutes to uniformly distend the small bowel before scanning. The volume of enteral contrast administered to the patient and the length of time that they are asked to ingest contrast vary by institution. In CTE, images are acquired 50 to 60 seconds after IV-contrast administration, corresponding to the mesenteric phase of enhancement that is best for evaluating the bowel, as opposed to the later portal venous phase acquisition used for conventional CT. Image acquisition lasts only a few seconds, which is advantageous for small children who may not tolerate long studies. CTE is the preferred CT technique for evaluating patients with IBD who are nonacute (7). CTE can delineate patterns of mural enhancement that aid in differentiation of acute versus chronic inflammation. Likewise, it allows excellent assessment of mesenteric inflammation, stricture, and fistulas. Conventional CT with IV contrast and either positive or no oral contrast is, however, preferred for acutely ill patients in whom there is a risk of bowel obstruction, perforation, or abscess, or who may be too ill to ingest the volume of enteric contrast required for enterography. The CTE sensitivity and specificity for the diagnosis of IBD based on meta-analysis of pooled data in children and adults are 84.3% and 95.1%, respectively (9). CT features of active bowel inflammation include bowel wall thickening, mucosal hyperenhancement, mesenteric hyperenhancement, fibrofatty proliferation, and mesenteric lymphadenopathy (Fig. 2). Fistulizing CD is often associated with extraluminal collections of air or fluid on CT.

FIGURE 2

FIGURE 2

The main disadvantage of CT is the ionizing radiation exposure to patients, which will be discussed in more detail in the subsequent section on radiation risk. Estimated effective dose for CT of the abdomen and pelvis in children ranges from 3 to 10 mSv, depending on patient size and technical factors (10). Radiation exposure to young patients associated with diagnostic imaging has received much attention in both the medical and lay press (11–12); it should be pointed out that present CT imaging is associated with significantly less radiation compared with older technology, which was the basis for many retrospective epidemiologic dose studies. Recent advances in CT hardware, scanning software, and postprocessing algorithms have dramatically reduced CT effective dose and made submilliSievert (ie, below annual background radiation exposure levels) CT scanning of the abdomen and pelvis possible (13). Another disadvantage of CT is that it is a single static phase examination and does not provide dynamic or functional information that can be acquired with MRE, US, or SBFT. This dynamic functional quality may increase the ability to detect and characterize bowel pathology. In comparison with MRE, CTE does not provide a way to look at underdistended bowel loops over time with multiple sequences.

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Enteroclysis (CT, MR, and Traditional Fluoroscopic)

Enteroclysis is a technique for evaluating the small bowel that consists of direct catheter instillation of enteric contrast via nasojejunal (NJ) intubation with a balloon tip catheter. In traditional fluoroscopic enteroclysis, a combination of barium and air or methylcellulose is instilled in a controlled fashion via gravity, syringe, or pump, producing both uniform distension of the small bowel and thin coating of the mucosal surface with contrast (14–16). Historically, fluoroscopic enteroclysis was the imaging criterion standard for diagnosing CD of the small intestine (17,18) owing to its high sensitivity for detecting subtle strictures and mucosal inflammatory changes (including ulcerations and nodularity) related to catheter instillation of enteric contrast and double contrast technique (Fig. 3A). A major limitation of fluoroscopic enteroclysis is its poor ability to detect extraluminal complications and extraintestinal manifestations of IBD. As a result, enteroclysis techniques using CT or magnetic resonance imaging (MRI) instead of fluoroscopy have been developed that combine cross-sectional evaluation of extraluminal/extraintestinal as well as intramural disease (Fig. 3B). CT enteroclysis (19) typically consists of NJ intubation and instillation of intermediate-density enteric contrast under fluoroscopic guidance until the small bowel is uniformly distended, followed by patient transfer to the CT scanner for imaging with IV contrast. The special enteric contrast used in these cases is visible by fluoroscopy while minimizing CT beam hardening, an artifact wherein the enteric contrast causes the edges of the lumen to be brighter than the center, potentially obscuring pathology. MR enteroclysis can usually be performed entirely within the MRI suite, with NJ intubation and enteric contrast administration performed under MR fluoroscopic guidance (thick slab cinematic acquisitions to see bowel peristalsis), followed by diagnostic MRI with sequences similar to those used for MRE (20).

FIGURE 3

FIGURE 3

The other major limitations of the enteroclysis technique include long examination time and the invasiveness of NJ catheter placement, particularly in young patients (Table 1). NJ intubation of children and adolescents with IBD frequently requires the use of moderate IV sedation, and even then it may not be well tolerated. For enteroclysis, patients are kept fasting for 8 hours before the procedure in case moderate IV sedation needs to be given (Table 1). Although MR enteroclysis has no radiation exposure, the requirements for MRI scanner time and procedural sedation while in the magnet can present logistical problems at many imaging centers. CT enteroclysis is often easier to perform because it combines fluoroscopic enteroclysis with diagnostic CT; however, it is associated with ionizing radiation exposure that is the sum of the 2 procedures. Although there are little to no data in children on enteroclysis radiation dose, a 2011 study of CT enteroclysis in adults estimated the effective dose from the enteroclysis portion of this examination alone to be approximately 5 mSv (21). Because of its combination of invasiveness and ionizing radiation exposure, CT enteroclysis in pediatric patients is often reserved for diagnostically challenging situations in which other modalities fail to detect an abnormality.

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MRI and MRE

MRI enjoys many inherent advantages over other cross-sectional imaging modalities and is increasingly being used as the primary imaging modality for young patients with IBD (22–24). Because of the lack of ionizing radiation, the bowel can be imaged by MR at multiple time points during an examination (ie, before and at serial times following IV-contrast administration), providing a dynamic assessment of mural signal intensity and enhancement to assess both active and chronic inflammatory changes. These sequences are especially helpful for discriminating active inflammation from fibrosis in patients with established disease (25). In addition, cinematic images of a thick volume of tissue can be obtained sequentially over time to evaluate bowel peristalsis, in an MRI analog to fluoroscopy (26). MRI does have its limitations compared with CT, particularly for evaluating young patients. These include inferior spatial resolution, potential image degradation from patient motion (respiratory and peristaltic) and susceptibility artifacts (owing to air within bowel), long examination times (30–60 minutes), and potential inability of young patients to tolerate awake scanning. The widespread adoption of new, faster MRI pulse sequences, as well as the availability of child life specialists and age-specific MRI educational tools, has, however, significantly reduced scanning time and opened the door for small bowel imaging in young patients (27,28). Susceptibility artifacts from air on MRI can also occasionally be an issue in evaluating acutely ill patients with IBD, in that subtle foci of free intraperitoneal air or extraluminal air within abscesses may be obscured by MRI and may be better visualized on CT.

As with CT, multiple different MRI protocols exist for examining the abdomen and pelvis in young patients with IBD (23,24,29,30). The primary MR examination is MRE, which combines large-volume enteric contrast distention with dynamic images pre– and post–IV-contrast administration to evaluate the presence of disease in the small bowel. The other primary MRI technique is pelvic MRI to evaluate for the presence and anatomic location of perianal disease (31). Because of the exquisite ability of MRI to detect small fistulae and define their anatomic relations to the anal–sphincter complex, pelvic MRI is the study of choice for evaluating perianal disease and planning treatment (32) (Fig. 4).

FIGURE 4

FIGURE 4

Although an in-depth discussion of the various pulse sequences used in abdominal MRI imaging is beyond the scope of this text, a familiarity with the commonly used sequences is valuable in understanding the applicability of MRE (29,30,33). T2-weighted imaging is useful in evaluating the bowel wall for the presence of T2-hyperintense edema that is strongly associated with active inflammation. Single-shot turbo spin echo (eg, single-shot fast spin echo or half-Fourier acquisition single-shot turbo spin echo) sequences produce high-quality, motion-free T2-weighted images of the entire bowel (34). Balanced steady-state free precession sequences (eg, fast imaging employing steady-state acquisition or true fast imaging with steady-state free precession) are T1- and T2-intermediate-weighted sequences that are rapid and demonstrate increased conspicuity of the mesentery for detection of inflammatory changes or fistula formation (35). These sequences, owing to their rapidity, can be performed as thick slab cinematic acquisitions to evaluate bowel peristalsis, known as MR fluoroscopy. Pre– and post–IV-contrast T1 fat-suppressed sequences are performed using 3-dimensional techniques to accelerate image acquisition and enable dynamic evaluation of bowel enhancement at multiple time points postcontrast, with early mucosal and progressive transmural enhancement being a hallmark of active bowel inflammation. An average imaging time for MRE, exclusive of the time required for enteral contrast administration, is approximately 30 to 45 minutes. Pelvic MRI does not require enteric contrast and has a scan time similar to MRE. MRE findings suggestive of active disease include bowel wall thickening, T2 mural hyperintensity, and mucosal hyperenhancement (Fig. 5).

FIGURE 5

FIGURE 5

There is no specific bowel preparation before MRE or pelvic MRI, but patients generally are kept NPO for several hours before the examination. Antiperistaltic agents such as glucagon may help improve image quality and are often administered just before imaging (36). IV contrast with a gadolinium-chelate–containing agent is routinely administered. There are several options in enteral contrast, which can be categorized by MRI signal characteristics. The most commonly used class of MR enteral contrast agents is the “biphasic” type, which is T1 dark and T2 bright. With these agents, one can readily assess the pattern of bowel wall folds on T2-weighted images without losing mucosal enhancement data on T1-weighted images (37). Contrast agents are often hyperosmolar, thereby drawing in water into the bowel lumen to maximize distention; an important adverse effect for patients to be aware of is diarrhea.

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Bowel US

High-resolution bowel transabdominal US has been used in Europe for >20 years but is only now emerging in North America as a valuable tool in the evaluation of a child with IBD. The main impetus for using bowel US is the lack of ionizing radiation or need for sedation and comparatively lower cost (Table 1). Therefore, it is an ideal option for imaging children <7 to 8 years, who would otherwise require sedation to undergo examinations such as MRE. The patient preparation is simple and entails NPO to solids 4 hours before the study and avoidance of all carbonated beverages. We encourage the children to drink clear liquids before the examination to reduce bowel gas that may obscure visualization and to push bowel loops out of the pelvis for easy compression. The present technique uses anterior and posterior compressions with a high-resolution (12–18 mHz transducer) probe scanning in a clockwise fashion from the right lower quadrant to the left lower quadrant. All segments of the colon and small bowel, including terminal ileum and jejunum, are imaged in 2 planes with grayscale and color Doppler. Our protocol also includes imaging the gastric wall and duodenum after the patient drinks water. Although in most children imaging the bowel segments is relatively easy, there are challenges, particularly in visualization of the rectosigmoid region as well as imaging the postoperative patient and those with a large body habitus. Bowel US requires experience and training of technologists as well as experience in interpretation; therefore, it is not widely accessible (Table 1).

The same imaging features of IBD, particularly of patients with CD, which are readily seen on CTE, barium studies, and MRE, are also depicted by US. US provides anatomical and functional imaging as we can assess in real-time peristalsis. The most common abnormalities are bowel thickening with hyperemia, irregular bowel wall, luminal narrowing, thickened echogenic mesentery, lymphadenopathy, and fluid collections/abscesses (Fig. 6). Based on published pediatric studies wherein the reference standards were based on ileocolonoscopy and histology, the diagnostic performance of US in the detection of disease had a sensitivity of 74% to 88% and a specificity of 78% to 93% (38), and in particular, the sensitivity for detection of terminal ileum disease is >90%. Canani et al (39) showed that in the setting of abnormal laboratory tests and increased bowel wall thickening, the positive predictive value for the diagnosis of IBD was 99.5%. In the detection of intraabdominal abscesses, US performs with a sensitivity of 83% to 91%. US, however, has a poorer performance in the detection of stenoses (38,40). Presently, high-resolution US is not as sensitive as CT or MRE for the evaluation of IBD complications or in distinguishing CD from ulcerative colitis. US may not be as comprehensive in imaging intramural and extramural pathology as MRE or CT; however, use of IV and enteric contrast agents may improve its sensitivity in the future.

FIGURE 6

FIGURE 6

In addition to transabdominal US for the assessment of CD, transperineal US (TPUS) has also been described for the evaluation of perirectal disease in perianal CD. Although the authors have no experience with TPUS, a 2013 publication in adults comparing TPUS and MRI of the pelvis shows that the sensitivity in experienced hands in detecting perianal fistulae is 94.4% (41); however, TPUS only correctly classified and detected fistulae and associated abscesses in 67.3% of patients. The agreement in classification of fistulae between MRI and TPUS was only fair. The TPUS has limitations in that it cannot assess deep fistula tracts and abscesses, and gas in abscesses or bowel can result in artifacts obscuring pathology. For these reasons MRI is more advantageous to provide a complete evaluation of the pelvis and perineum.

In the authors’ experience, transabdominal US wherever available can be best used in the diagnosis or confirmation of IBD in children, particularly in the younger group, to avoid sedation, to study patients who have localized terminal ileal disease and disease progression after a baseline MRE or CTE, and to study abscesses while children are being treated or following catheter drainage.

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RADIATION RISKS

The discussion of the radiation effects from medical imaging is an evolving topic. A full historical discussion of radiation exposure risk extrapolated from Japanese atomic bomb survivors and a discourse in radiation biology is beyond the scope of this article. Present belief suggests an overall increased risk of cancer, with exposure to low-dose ionizing radiation approaching that associated with diagnostic imaging, particularly CT scans (11,12,42). There are several reasons why children are at a particularly increased risk, including earlier exposure of radiosensitive growing tissues and generally smaller body habitus leading to increased exposure to sensitive organs. Pediatric patients with CD are a particularly vulnerable population because of their likelihood to undergo multiple CT or SBFT studies for a short period and during the course of their lifetime. In addition, patients with IBD are recognized to have a long-term increased risk of gastrointestinal malignancy and may be at increased risk for extraintestinal malignancies, including lymphoma, leukemia, and skin cancers (43). Immunododulator and biological pharmacotherapy may also contribute to slightly increased risk of malignancy (44–46). The ionizing radiation risk of diagnostic imaging studies stems from an increased probability of radiation-induced stochastic DNA damage at low dose exposures (47); however, it is unclear whether the effects of multiple imaging studies separated over time are cumulative. It is also important to keep things in perspective and remember that the theoretical mortality risk from a single CT scan is far less than that associated with other causes, including catching influenza or getting struck by a car (48).

Based on the published pediatric literature, the average annual cumulative effective dose (CED) acquired by a child with IBD from medical imaging is 3 to 5 mSv (42,49,50), which is comparable to the annual background radiation exposure that all children receive from environmental sources living at sea level (summarized in Tables 2 and 3). Fuchs et al have also shown that patients with CD receive on average a higher annual CED from imaging studies than patients with UC because of more frequent symptomatic exacerbations and the need for small bowel evaluation. The actual CED threshold from imaging associated with the development of cancer is not clear, although data extrapolated from cancer risk in nuclear radiation workers suggest a nonzero cancer mortality risk at CED >75 mSv (51). A study from Europe found that 16% of patients with CD had a CED >75 mSv from diagnostic imaging for a 15-year period, the vast majority of which was from CT scans, with diagnosis at <17 years of age being a significant risk factor for higher CED (52). Other risk factors for high CED include multiple surgeries, multiple hospitalizations, penetrating extraluminal disease, higher Crohn's Disease Activity Index (CDAI), and requirement of IV steroids or infliximab (50,52).

TABLE 2

TABLE 2

TABLE 3

TABLE 3

It is clear that radiation dose exposure from diagnostic imaging studies should be monitored and recorded, although how this information is best used remains a topic of active debate. Some authors suggest that this information should be used to set a CED threshold based on patient imaging history, above which imaging studies involving ionizing radiation would be avoided (53). Others have, however, argued that the linear no-threshold model, which is presently accepted for radiation risk, implies that each imaging study (eg, the first or the 10th CT) contributes equally to a patient's CED and risk and that present medical decisions should not be changed based on past radiation exposure (54,55). An additional controversial topic is the concept of radiation hormesis, which proposes that low-level ionizing radiation can stimulate protective/reparative molecular and cellular processes (56). Although there is literature supporting this potential beneficial effect, more rigorous studies are needed to validate this principle and decide how to reconcile this concept with the known adverse effects of higher-dose radiation. It seems reasonable to adopt a policy that, given the likelihood the pediatric patients with IBD will be exposed to medications associated with slightly increased risk of malignancy and will require a number of imaging studies during their lifetime, imaging modalities and protocols should seek to minimize patient radiation dose at any level of prior radiation exposure, provided the imaging study selected is effective in answering the clinical question.

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IMAGING ALGORITHMS

Despite a full understanding of the myriad imaging modalities available, it is consistently challenging to select an imaging examination. Therefore, we propose a few common clinical scenarios with algorithms for selecting an appropriate test. These are merely guidelines and recommendations based on the few existing pediatric original articles (Table 4) (9,22,25,42,57–59) and the authors’ experience, taking into consideration that imaging is also variable among pediatric IBD centers. In general, we suggest finding strategies that provide the needed information while still minimizing diagnostic radiation exposure.

TABLE 4

TABLE 4

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Scenario 1: Undiagnosed or Suspected IBD

Patients suspected of having IBD are divided into 2 risk profiles: low risk and high risk, based on symptoms, physical examination, laboratory evaluation, and family history. Often in these situations endoscopy has not yet been performed, but imaging is desired (Fig. 7). Based on availability, in low-risk patients, MRE and bowel US are the recommended imaging studies for bowel assessment, obviating exposure to ionizing radiation. If neither MRE nor bowel US is available, then a barium study is the next option. Bowel US is a good choice in experienced hands owing to its relatively good negative predictive value for the diagnosis of IBD, especially in the absence of bowel wall thickening. It can be easily performed in young children <9 years old who require sedation for an MRI rather than SBFT, which uses ionizing radiation. As described by Absah et al (59), it is challenging to perform MRE in children <9 years old, primarily because of anxiety and the inability to hold still, which greatly affects image quality. In our experience we have imaged children as young as 7 years successfully, but these are rare, unique situations. Anecdotally, some institutions are successfully using child life services to perform MRE in patients as young as 4 to 5 years of age. The use of sedation for MRE is institution specific and not possible in most places because the oral contrast that is required violates NPO guidelines. Barium UGI imaging with small bowel series can be helpful in this population to identify alternate causes of chronic abdominal pain or diarrhea in young patients. In high-risk patients with a stronger chance of IBD, the preferred methods of evaluation for the bowel is enterography using CT or MR, given the high accuracy of both techniques for detecting active bowel inflammation.

FIGURE 7

FIGURE 7

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Scenario 2: Newly Diagnosed IBD

The 2 suggested options for this subset of patients are MRE and CTE (Fig. 7). Both modalities provide a comprehensive global look at the small and large bowels and identify potential complex penetrating disease or complications. The advantages of MRE are that it is comparable with CTE in detecting active disease and there is no ionizing radiation. Some institutions prefer CTE as the initial baseline study in newly diagnosed patients with IBD because it affords higher spatial resolution for subtle skip areas and may be better tolerated in those who cannot drink large volumes of oral contrast or in whom MRI is contraindicated.

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Scenario 3: Established Disease—What to Do to Assess Complications

The complications in children with IBD are commonly seen in the CD group and are listed in Table 5. In acute emergent situations and after hours in which a child is critically ill, CT plays an important role in the assessment of intraabdominal abscesses and immediate postoperative complications. Beyond this, we suggest MRE as the optimal examination in evaluating more longstanding disease complications.

TABLE 5

TABLE 5

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CONCLUSIONS

Imaging clearly plays an important role in the management of new and existing patients with IBD, providing noninvasive initial diagnosis and characterization of disease, as well as subsequent determination of disease activity and treatment response. Our imaging arsenal has grown during the last decade, bringing with it more sophisticated examinations that can be used in a variety of clinical scenarios. We hope that current thinking based on the vast and expanding literature on radiation effects from diagnostic imaging has been presented in a clear manner. The clinical/imaging pathways are meant to be a guide to the pediatric gastroenterology practitioners in any practice, knowing well that there may be exceptions to these algorithms based on individual institutional practice patterns, availability of certain modalities, and patient factors. Pediatric gastroenterology practitioners should be familiar with all of the available imaging tools and choose the best ones for each clinical scenario. Whenever possible, alternatives to conventional studies using ionizing radiation should be considered.

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Acknowledgment

The authors thank Winnie Zhu, PhD, physicist in the CHOP Radiology Department, for contributions of the data and table on estimates of effective dose from various examinations.

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Keywords:

children; imaging; inflammatory bowel disease; radiation dose

© 2014 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology,