Imaging description

Undistended or contracted bowel may appear as focally narrowed segments with circumferential wall thickening and so mimic stricture or tumor (Figures 65.1 and 65.2).

Importance

A false positive diagnosis of bowel pathology may lead to unnecessary testing and anxiety.

Typical clinical scenario

Pseudotumor due to undistended bowel is most commonly seen in the colon or rectum as an incidental finding at CT performed for unrelated reasons.

Differential diagnosis

Physiological bowel wall thickening due to under-distension or contraction is a well-recognized finding at fluoroscopy, but is usually easily recognized on such a dynamic investigation because it is transient. This pitfall can be much more problematic on a static study such as CT. While the upper limit of colonic wall thickness is usually considered to be 3–5 mm [1, 2], a thickness of up to 8 mm has been reported in contracted normal colonic segments [3]. As such, wall thickening in a non-distended segment of bowel should be interpreted cautiously. The absence of additional signs of pathology such as altered wall density or enhancement or perimural fat stranding may point towards a physiological etiology.