الفهرس 
Anatomy of the Small BowelOnly 14 pages are availabe for public view
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Abstract
Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the bowel. The major types of IBD are crohn’s disease (CD) and ulcerative colitis. Both disorders characterized by unpredictable periods of remissions and exacerbations. These disorders need to be distinguished from other conditions that may display similar clinical and laboratory findings, such as infection, allergy, and neoplasm.
The radiologic diagnosis of ulcerative colitis & crohn’s disease is challenging. It includes a variety of examination techniques that must be performed & interpreted with care if the radiologist has to make a significant contribution to patient management. An understanding of the anatomic and patho-physiologic basis of the radiologic features of IBD is important to fully appreciate the natural history and differentiating features of these perplexing diseases.
For many years, the radiologic modality most commonly used to evaluate the small bowel has been the conventional small bowel follow through (SBFT). Newer imaging methods including computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound are valuable tools in assessing intestinal wall and extra-luminal involvement.
Conventional radiographic imaging studies still playing a role in the workup of patients with suspected IBD and in the differentiation of ulcerative colitis and Crohn’s disease. Because of its ability to depict fine mucosal detail, the double-contrast barium study is a valuable technique for diagnosing UC & CD even in patients with early disease.
In contrast, cross-sectional imaging studies such as CT, MRI and ultrasound are useful for showing the effects of these conditions on the wall of the bowel and also for demonstrating extra-luminal findings in patients with more advanced disease. Thus, barium studies and cross-sectional imaging studies have complementary roles in the evaluation of these patients.
In experienced hands, trans-abdominal US is an accurate method for the detection of intestinal complications in Crohn’s disease. Trans-abdominal US is thus used as a primary investigative method for evaluation of severe crohn’s disease.
There is growing concern among the medical community that diagnostic radiation adds to the already increased risk of developing lymphoma that may be inherent in or related to ionizing radiation exposure during diagnosis of IBD.
As a result, MRI has been advocated as one of the most important techniques for small bowel imaging. MRI is able to detect significant variations in bowel wall thickness and contrast enhancement, reflecting favorable clinical response to medical treatment of IBD’s relapse. Also, the modality can provide an accurate assessment of disease activity, producing multi-planar images with high soft-tissue contrast in addition to the advantage of using non-ionizing radiation, making MRI the imaging technique of choice for the follow-up of patients with active IBD. Also the discomfort and risks are lower than with other methods.
Although most of the studies on virtual colonoscopy are dealing with the role of detecting colo-rectal polyps or neoplasms. Depicting colonic wall thickening through MR colonography (MRC) seems to be a useful tool in the diagnosis of crohn’s colitis. The thick walled segments with narrow lumen seen on MR colonography corresponding to the regions where colonoscopy failed to pass. Air filled sinus tracts, thickening of the wall of the terminal ileum, loss of haustration, pseudo-polyps and deep ulcers are seen in MR colonography. Three dimensional (3D) endo-luminal views demonstrat pseudopolyps similar to endoscopic images. Only shallow and aphtoid ulcerations or granular mucosal surface detected colonoscopically can not be observed on MR colonographic images.
In conclusion, MRI can be a reliable non-invasive technique for diagnosis and evaluation of IBD. The role of MRI is essential in assessment of extra-luminal extension, abscess formation, fistulation and other complication of IBD, in which barium studies and endoscopy are of limited value. Also, MRI findings showing good correlation with inflammatory bowel disease activity.
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