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.
Statistics on Small Bowel Cancer (Adenocarcinoma of the Small Intestine)
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.
Risk Factors for Small Bowel Cancer (Adenocarcinoma of the Small Intestine)
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 of Small Bowel Cancer (Adenocarcinoma of the Small Intestine)
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.
How is Small Bowel Cancer (Adenocarcinoma of the Small Intestine) Diagnosed?
With small bowel cancer a Full Blood Count may reveal anaemia due to chronic lower gastrointestinal (GI) blood loss with iron deficiency. Liver function tests may be abnormal due to obstructive jaundice or disease. An abdominal x-ray may reveal a small bowel obstruction.
Prognosis of Small Bowel Cancer (Adenocarcinoma of the Small Intestine)
The overall prognosis is poor for small bowel cancer – but that is because it is usually advanced at the time of presentation, making surgical management difficult or impossible. However, without lymph node metastases the 5 year survival is 60%.