Most inflammatory, neoplastic and vascular disorders manifest bowel wall thickening on computed tomography (CT). Therefore, it is very important to understand the patterns of bowel wall involvement (degree, length, symmetry and contrast enhancement patterns) in each category to make a correct diagnosis. Observing extraluminal changes also help to classify the primary causes of pathological conditions involving the gastrointestinal tract. Adequate CT examinations with optimal opacification of the gastrointestinal tract are essential not only to avoid false positive findings but also to detect subtle or minimal lesions. If findings for establishing a diagnosis are equivocal, the use of combined findings increases the diagnostic accuracy of CT.