adenocarcinoma of the small bowel

Malignant

enterocutaneous fistula in Crohn"s disease. Pre-(a,b) and corresponding post-contrast (c,d) multiplanar images showed two ventral enterocutaneous fistulas (arrowheads) with fluid and air content, plus a markedly thickened ileal segment (arrows) infiltrating the abdominal wall.

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Primary adenocarcinoma of the small bowel is about 50 times less common than colonic carcinoma.

Pathology

Almost 50% of small bowel adenocarcinomas are found in the duodenum, especially near the ampulla. In the remaining cases, the jejunum is more commonly involved than the ileum.

Risk factors include a history of:

Crohn disease;
Sprue;
Peutz Jeghers syndrome;
Lynch syndrome II;
congenital bowel duplication;
ileostomy or duodenal or jejunal bypass surgery.

More distal small bowel adenocarcinomas are more likely to be annular, duodenal adenocarcinomas tend to be papillary or polypoid.

Radiographic features

CT

CT shows a soft-tissue mass with heterogeneous attenuation, usually with moderate enhancement after intravenous administration of contrast material.
may manifest as an annular narrowing with abrupt concentric or irregular “overhanging edges,” a discrete tumor mass or an ulcerative lesion.
usually, only a short segment of the bowel is involved. Gradual narrowing of the lumen leads to partial or complete small bowel obstruction.

A large, aggressive, ulcerated adenocarcinoma can be mistaken for lymphoma. However, lymph node metastases in adenocarcinoma are usually less bulky than those in lymphoma.