Anjali Shroff, B.S.
Kristopher Lewis, M.D., Assistant Professor of Radiology, MCG
Clarence Joe, D.M.D., M.D., F.A.C.R.
Sateesh R. Prakash, M.D., SGS Research and Educational Institute, LLC
Radiologic Imaging in Inflammatory Bowel Disease (IBD)
Crohn’s disease (CD) and ulcerative colitis (UC), collectively known as inflammatory bowel disease, are increasingly prevalent in the United States with an estimated incidence of 400 patients per 100,000 individuals.1 In addition to the endoscopic evaluation and clinical symptoms, radiologic evaluation is an important component to the diagnosis and management of IBD.2
Various imaging studies are utilized by physicians in treating CD and UC. Plain radiographs, computerized tomography (CT scans), and magnetic resonance imaging (MRI) are a few examples of such studies. In evaluating which method to use, doctors must take into account the patient’s age, possible complications associated with imaging, financial cost, radiation exposure, and availability of tests. Older methods of imaging include radiographs which can evaluate for complications of disease such as obstruction and amount of stool, though they are not used for diagnosis of IBD. CT scans are increasingly utilized in the acute setting to evaluate for complications of IBD which include small bowel obstructions, abscesses, and perforations.1 Relatively newer techniques such as CT enterography, which uses a CT scanner with oral contrast for imaging, and MR enterography, which uses magnetic resonance imaging, have been shown to be successful in assisting with the diagnosis of IBD particularly the extent of involvement including fistulization, perianal disease and small bowel involvment. MR enterography is specifically more desirable due to its lack of radiation and increased accuracy.1 However increased costs and lack of availability are drawbacks to MR enterography. MR and CT enteroclysis are techniques that employ contrast administered through a nasojejunal tube in order to distend bowel. MR enterography is more commonly used in children due to the specialized skill needed and lack of availability of MR enteroclysis.1 CT enteroclysis is usually better suited for acute situations such as obstruction or abscess. To assess for perirectal abscesses or fistulas, literature has shown MRI to be the best imaging modality to determine presence, type, location, and associated findings of fistulas.1
Traditionally, small bowel follow-through (SBFT), which is an xray of the bowel after ingestion of contrast, or enteroclysis, a fluoroscopic evaluation of the small intestine, were used as a gold standard to evaluate bowel disease.3 Drawbacks to SBFT include the high radiation dose, poor imaging of the bowel causing difficulty in evaluation of the disease, and inability to evaluate disease spread outside the bowel.1 Recently, video capsule endoscopy (VCE) and double-balloon endoscopy (DBE) have allowed for more diagnostic techniques to fully evaluate bowel disease and the extent of CD. VCE involves swallowing a small capsule containing a camera which takes pictures of the bowel.3 One of the limitations of using a capsule is capsule retention resulting from a stricture or other obstructive process in the bowel lumen.4 In addition to visualizing the entire small bowel, DBE allows for biopsies and therapeutic intervention.3
In order to evaluate all layers of the bowel, other imaging techniques such as ultrasound (US), CT scans, or MRI may be used. For US, the patient is usually required to fast for 4 hours or overnight, depending on the situation.3 Using Doppler US also allows for evaluation of vessels that supply the bowel.3 Other findings on US that can help identify IBD include deep abscesses, ulcers, fistulas, and changes to the bowel wall.3 The stratification pattern of the bowel wall is an important feature of distinguishing CD from UC since it is variable with CD.3 Some disadvantages of using US to detect IBD is that certain parts of the small bowel, such as the duodenum, jejunum, rectum, and sigmoid colon, are not clearly visualized, the extent of disease cannot be fully evaluated, sensitivity is low for detection of superficial mucosal disease,4 and small abnormalities may not necessarily be detected.3 However, if an imaging technique is required, US is a good initial imaging option since it is inexpensive and easily conducted.3
For a CT scan, patients are usually asked to fast for a few hours and oral and intravenous (IV) contrast is used.3 As with US, IBD is diagnosed by thickening of the bowel wall of greater than 3 mm. With IV contrast, an increase in enhancement with CT imaging of the bowel wall, especially throughout all the layers, can also suggest IBD.2 One disadvantage of the CT scan is significant radiation exposure.
For MRI, depending on the facility, fasting or bowel cleansing methods are used prior to the exam. The bowel must be distended with contrast to fully elucidate any pathology. An advantage of MRI is the lack of radiation exposure.3 With MRI, a thickened bowel wall (>3mm) is used to diagnose IBD as well as enhancement of the bowel wall.3 MRI is very sensitive in detecting fistulas, abscesses, and enlarged lymph nodes.1 Some disadvantages of MRI include the prolonged imaging time and the possible necessity of medications to slow gut motility for improved imaging.
IBD in the pediatric population usually presents more extensively and severely.2 Due to the possibility of vitamin malabsorption and subsequent growth retardation, diagnostic accuracy in this population is essential.2 MRI can be used to help detect strictures, disease through all layers of the bowel, and other pathology in children since there is no radiation exposure.4 Radiation with fluoroscopy and CT studies is a concern, especially in the pediatric population, hence other studies such as MRI, US, or capsule endoscopy are preferred.2 In emergencies, CT is still a useful tool for rapid imaging in children and to evaluate complications of IBD.4
Overall, it is important to discuss radiographic tests with your doctor to identify the appropriate tests in the management of your IBD.
1. Pediatr Radiol. 2009: 39(2): 149-152. Imaging choices in inflammatory bowel disease. Anupindi SA, Darge K.
2. Dig Dis. 2009: 27: 269-277. Inflammatory Bowel Diseases: Controversies in the Use of Diagnostic Procedures. Vucelic B.
3. Abdominal Imaging. 2008 July: 33: 407-416. Detection of inflammatory bowel disease: diagnostic performance of cross-sectional imaging modalities. Horsthius K, Stokkers PC, Stoker J.
4. Pediatr Radiol. 2008: 38 (3): 512-517. Imaging of inflammatory bowel disease. How? Hiorns, MP.