الفهرس 
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Abstract
Small bowel is affected by a group of diseases that can be categorized into inflammatory bowel disease, small bowel neoplasm, infections and congenital diseases. Inflammatory bowel diseases particularly crohns disease are characterized by unpredictable periods of remissions and exacerbations.
Diagnosis of small bowel diseases requires both the clinical information, and the important role of the radiologic imaging. Few years ago, barium studies and endoscopy were considered the dominant modalities in evaluation of small bowel diseases with endoscopic guided biopsy and histopathological verification. However, the introduction of multislice CT and MRI technologies began to change this concept as these new imaging modalities enabled faster acquisition of a larger amount of information and led to better details of the intestines and mesenteries.
MDCT and CT enterography have a disadvantage of involving considerable ionizing radiation exposure especially in patients with inflammatory bowel diseases who were diagnosed early in life and require frequent follow up imaging.
Recently, advances in magnetic resonance imaging (MRI) technology with the introduction of fast MRI sequences and three-dimensional post-processing abilities offer sensitive and radiation free imaging for small bowel inflammatory diseases with proper evaluation of abnormalities of the small bowel wall and extra-luminal changes.
Medical and surgical treatment of small bowel diseases are greatly affected by the extent, activity of the disease, the presence of penetrating lesions and intestinal obstruction which may alter the management decision. Therefore, assessment of small bowel lesions is not only including the accurate diagnosis, but also it is important to evaluate the extent, activity, severity of the disease and assess its complications.
MRE had high sensitivity, specificity and accuracy in diagnosis of small bowel lesions specially IBD and detection of its complications. Also, it was observed that MRE is a reliable predictor of Crohn’s disease activity (as active and inactive disease) in a way comparable to endoscopy with high significant agreement between MRE and endoscopy in the detection of small bowel stricture, but there was no significant agreement in detection of small bowel ulcers in Crohn’s patients.
So, we recommend further researches and investigations to be done regarding the MRE signs of active inflammation in order to establish MRI quantitative index for Crohn’s activity and severity, to be correlated with Crohn’s disease endoscopic index of severity (CDEIS), thus to be valid for use in clinical practice in assessment of Crohn’s disease activity and severity as well as for follow up.
We also recommend further studying of the role of diffusion and perfusion in the assessment of Crohn’s disease activity.
Recently, new studies were conducted on Magnetization transfer imaging to help detection of fibrosis, and found out that Magnetization transfer ratio correlates with tissue collagen levels and is sensitive to changes in fibrosis over time. This can provide a noninvasive method for determining the fibrotic content of small bowel strictures in Crohn’s disease, and so will greatly affect management decisions.
To conclude, although MRE is observed to be a powerful imaging tool for diagnosis of small bowel diseases, assessment of disease activity and detection of their complications, MRE is still currently used in combination with clinical and endoscopic data for assessment of inflammatory bowel disease activity and severity.
However, we can be confident that MR enterography will take over the primary role in the diagnosis, follow up, assessment of activity and severity of small bowel inflammatory diseases in the very near future.