الفهرس 
Anatomy of the IntestineOnly 14 pages are availabe for public view
 |  | from | 177 |  |  |
| | | from | 177 | | |
Abstract
In recent years, several radiologic techniques have been developed for the study of the small and large bowel. Each technique is characterized by its own profile of advantages and disadvantages.
Because of the relapsing nature of Crohn’s disease and the young age at which it usually develops, frequent reevaluation of disease is necessary in many patients. Specific, noninvasive, well-tolerated, and inexpensive examinations should be carried out while studying Crohn’s disease. These examinations will have to confirmclinical suspicion of the disease as well as provide morphological information such as location, extension, or complication and recurrence evolution.
Examinations should also make functional information available for an effective management of the disease.
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 Crohn’s disease,it 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 Crohn’s disease. Cross-sectional imaging studies such as CT, MR, and ultrasound are useful for showing the effects of this condition 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 Crohn’s disease 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. Transabdominal 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 Crohn’s disease patients.
MRI is able to detect significant variations in bowel wall thickness and contrast enhancement, reflecting favorable clinical response to medical treatment of Crohn’s disease 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 Crohn’s disease.
With the introduction of spiral scanning then multidetector 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 -enteroc1ysis, 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 initial diagnosis, any investigation can be used, considering the experience of the structure and the operator; MSCT, MRE, or CE for the first diagnosis; US, and possibly supplemented with PD/CEUS, for followup; MRE, MSCT, or PET/CT for Relapses; MSCT, MRE, or CE for complications.