Small bowel cancer (Adenocarcinoma of the Small Intestine)

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What is Small bowel cancer?

Small bowel cancers include adenocarcinomas, carcinoid tumours, lymphomas, and leimyosarcomas. The small bowel is composed of the duedenun, jejenum, and ileum. It is the part of the Gastro-Intestinal tract extending from the pyloric sphincter of the stomach to the ileo-caecal valve separating the ileum from the colon (large bowel).

The small bowel is important for the breakdown and absorption of nutrients from digested food. Food that is partly digested by the acids in the stomach continues to be broken down by enzymes from the pancreas - which drain into the duedenum at the ampulla of vater. Bile salts from the liver and gallbladder also drain into the duedenum at the ampulla of vater. After further digestion, food constituents such as proteins, fats, and carbohydrates are broken down to small building blocks and absorbed into the enteric circulation.

Who gets Small bowel cancer?

Small bowel cancer (Adenocarcinoma (AC) of the small bowel) is not common overall - accounting for 3 to 6% of gastro-intestinal tumours, even though it represents 75% of the length of gastr-intestinal tract. Adenocarcinomas are the most common cancer of the small intestine - making up 40%. It occurs with increasing age, most commonly in the sixth or seventh decade.

Predisposing Factors

With small bowel cancer the most important predisposing factors are:

Crohn's disease - Usually distal ileum.
Familial adenomatous polyposis - This inherited condition almost invariably leads to colon cancer in affected individuals, though it less commonly causes adenocarcinomas in other parts of the gastro-intestinal tract. Most commonly this is in the region of the duedenum.
Adult coeliac disease .

Progression

These small bowel cancer tumours tend to progress with local extension initially, then lymphatic and distal spread to other organs. Local growth into the lumen of the intestine may cause bowel obstruction, and sometimes bowel perforation. Periampullary small bowel cancer tumours may also cause obstructive jaundice by obstructing bile flow into the ampulla of vater.

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