الفهرس 
Gross and Radiological Anatomy of Bowel LoopsOnly 14 pages are availabe for public view
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Abstract
Inflammatory bowel disease (IBD) is a generic term used mainly to describe two idiopathic disorders that are associated with gastrointestinal inflammation: Crohn’s disease (CD) and ulcerative colitis (UC). These disorders need to be distinguished from other conditions that may display similar clinical and laboratory findings, such as infection, allergy, and neoplasm.
The ultimate definition of UC and CD rests with the location and characteristics of inflammation within the gastrointestinal tract. In UC, a relatively homogeneous inflammatory process is confined to the mucosa, which starts in the rectum and involves a variable extent of colon proximally, while CD may involve any portion of the alimentary tract, from mouth to anus. Mucosal inflammation in CD may be generalized or patchy and may extend gradually into the submucosa, muscularis, and serosa. This transmural inflammation can result in further intestinal complications.
The radiologic diagnosis of ulcerative colitis & Crohn’s disease is challenging. It embraces a variety of examination techniques that must be performed & interpreted with care if the radiologist is 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.
Radiographic imaging studies have an important 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 ulcerative colitis and Crohn’s disease even in patients with early disease. In contrast, cross-sectional imaging studies such as CT, MR, and ultrasound are useful for showing the effects of these conditions on the wall of the bowel and also for demonstrating intra-abdominal abscesses and other extraluminal findings in patients with more advanced disease. Thus, barium studies and cross-sectional imaging studies have complementary roles in the evaluation of these patients.
Early manifestations of IBD such as enlarged lymphoid follicles, erosions, and aphthoid ulcers are well appreciated at colonoscopy and barium studies.
In experienced hands Transabdominal US is an accurate method for the detection of intestinal complications in Crohn’s disease. Transabominal US is thus recommended as a primary investigative method for evaluation of severe Crohn’s disease. Combination of B-mode and power Doppler sonography has a high accuracy in the determination of disease activity in IBD patients.
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. In addition to its lack of ionizing radiation, this may allow MRI to be the imaging technique of choice for the follow-up of patients with active IBD.
99mTc (V) DMSA scintigraphy cannot be used for the diagnosis of IBD(as it is not specific), but it can be recommended for use at follow-up and for assessment of disease activity in these patients.
With the introduction of spiral scanning then multi-detector technologies, the accuracy for diagnosing digestive tract diseases with CT has been highly improved, and CT is used more and more in the evaluation of patients with suspected gastrointestinal disorders. CT is able to demonstrate both the intramural and the extramural components of the disease, and has a major role in the preoperative staging and the follow-up. Improvements of CT protocols, such as CT-enteroclysis, or multiplanar 2D and 3D post-processing, including new techniques for ”virtual endoscopy”, lead to discuss new indications in which CT could now compete with conventional X-rays series and videoendoscopy.
Multi-detector row helical CT enteroclysis is well tolerated and allow the diagnosis of small-bowel masses and active Crohn’s disease. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of multi-detector row helical CT enteroclysis were 100%, 95%, 97%, 94%, and 100%, respectively.
Although Most of the studies on virtual colonoscopy are dealing with the role of detecting colorectal polyps or neoplasms. CT colonography by depicting colonic wall thickening seems to be a useful tool in the diagnosis of Crohn’s colitis. With CT colonography, the wall of bowel segments severely affected by the disease were depicted by the axial CT scans appear to be thickened. The thick walled segments with narrow lumen seen on CT colonography corresponded to the regions where colonoscopy was failed to pass. Air filled sinus tracts, thickening of the wall of the terminal ileum, loss of haustration, pseudopolyps and deep ulcers were seen in CT colonography. Three dimensional (3D) endoluminal views demonstrated pseudopolyps similar to endoscopic images. Only Shallow and aphtoid ulcerations or granular mucosal surface detected colonoscopically can not be observed on 2- or 3D CT colonographic images.
In conclusion, Multidetector CT can be a reliable noninvasive technique for diagnosis and evaluation of inflammatory bowel disease. The early changes of the disease do not require CT evaluation. However the role of CT is essential in assessment of extraluminal extension, abscess formation, fistulation and other complication of the disease, in which barium studies and endoscopy are of limited value.