الفهرس 
MRI manifestations of inflammatory bowel diseaseOnly 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 (UC). 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.
For many years, the radiologic modality most commonly used to evaluate the small bowel has been the conventional small bowel follow through. Newer imaging methods including computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound are valuable tools in assessing intestinal wall and extra-luminal involvement.
Barium studies and endoscopy are the basic modalities in diagnosing Crohn’s disease in early stages with endoscopic guided biopsy and histopathological verification, however, the M.D.C.T. has been the cross sectional imaging modality of choice at most institutions due to its widespread availability, low cost and higher spatial and temporal resolutions relative to M.R. imaging, yet it is based on ionizing radiation.
Although CT is widely used in the imaging work-up for Crohn’s disease, it carries a high radiation burden; it is preferable to use a non ionizing modality such as MR imaging for diagnostic and follow-up evaluations.
Because of the increased use of CT, high cumulative radiation doses may be imparted to patients with Crohn disease. A recent study reported that CT accounts for up to 84.7% of the cumulative radiation in patients and that 15.5% of patients with Crohn disease received doses of more than 75 mSv.
The carcinogenic effect of this amount of radiation is particularly significant because patients with Crohn disease already have an increased risk for developing gastrointestinal cancer, lymphoma and hepatobiliary cancer.
As a result MR imaging techniques can be used to detect and diagnose nearly all bowel disorders.
MR enterography is increasingly being used in the assessment of complex or recurrent Crohn disease. A time-efficient combination of HASTE and true FISP pulse sequences can be used to demonstrate most manifestations of enteric Crohn disease for clinical management. MR imaging of Crohn’s disease allows the depiction of both intra- and extraluminal disease without ionizing radiation and the risks associated with it. Even subtle disease
manifestations may be detected when adequate distention of the small bowel is achieved (MR enteroclysis). Further work is required to determine whether MR imaging enhancement patterns may reliably help discriminate between active and inactive disease; in our practice, however, the technique has proved sufficiently robust for routine implementation.
It is mainly indicated to diagnose inflammatory bowel disease, however it is also used for diagnosis many other bowel disorders such as post operative adhesions, celiac disease, radiation enteritis, jejunitis, eosinophilic gastroenteropathy, Sclerosing encapsulating peritonitis, TB enteritis and polyposis syndrome.
MR enteroclysis has been introduced in the workup of small-bowel diseases and become superior to other modalities even MR enterography as MR enteroclysis achieves excellent bowel distention and provides detailed luminal information and may demonstrate subtle transition points or an obstruction that may not be visible at imaging with more routine methods, including enterography.
MR enteroclysis has been advocated as it is able to detect significant variations in bowel wall thickness and contrast enhancement, reflecting favorable clinical response to medical treatment of CD’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 CD.
In recent study by (Massaelli.G et. al , 2008) found there is no significant difference between MR enteroclysis and MR enterography in the detection of mural stenosis, however MR enteroclysis delineates superficial changes better than MR per oral contrast to localizing the disease in patients with only superficial manifestations . For these reasons MR enteroclysis should be preferred as the initial study in patients with suspected Crohn’s disease, while MR per oral contrast can play an important role in patients who refuse or fail to have intubation and also for follow-up in patients with known Crohn’s disease.