Bowel wall thickening

Anatomy, embryology, pathophysiology

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  Most of the small and large bowels originate from the midgut, except the proximal duodenum (up to the ampulla of Vater), which originates from the foregut, and the portion of the colon distal to the proximal two-thirds of the transverse colon, which originates from the hindgut.

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  The blood supply follows the same distribution, where the bowel arising from the midgut receives most of its blood supply from the superior mesenteric artery, the portion arising from the foregut from the celiac artery and that arising from the hindgut mainly from the inferior mesenteric artery, with rich anastomosis between these arterial branches.

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  Normal intestinal wall thickness depends on the degree of bowel distention and the imaging modality. The normal jejunum wall thickness measures approximately 2 mm and the ileum 1 mm on enteroclysis. On computed tomography (CT), 3 mm for the small bowel and 5 mm for the large bowel are accepted as the upper limit of normal when the bowel is completely distended.

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  When considering the imaging findings that help narrow the differential diagnosis of a pathological bowel inflammatory condition, several factors are important. These include the length of involvement, location of involvement, degree of thickening, and extraintestinal manifestations of the disease. By carefully considering these anatomic considerations, the differential diagnosis can be considerably narrowed.