Most small bowel
polyps in
familial adenomatous polyposis (FAP) occur in the peri-ampullary region, and distal small bowel
adenomas and
carcinomas are comparatively less common. As standard
therapy in FAP consists of
proctocolectomy with
ileal pouch anal anastomosis, or ileorectal anastomosis, it is essential to be aware of the potential for
adenomatous polyp formation in the terminal ileum and rectum. Ileal
adenomas are found in 9-20% of patients with FAP, and new
polyps may develop after
colectomy. Ileal lymphoid
hyperplasia and
polyps are 2-4 times more common than
adenomas, may be indistinguishable from
adenomas on examination (requiring biopsy for diagnosis), and tend to regress after
colectomy.
Adenomas may arise in pouches, usually after an interval of several years, and have been documented to occur in the terminal ileum up to 25 years after
colectomy. At pouch construction, rectal mucosectomy may theoretically fail to remove all mucosa at risk. Small islets of rectal mucosa may remain after this technically difficult operation, and the late development of
cancer, up to 20 years postoperation has been noted. A stapled anastomosis may arguably have a better physiological result, but a greater amount of residual rectal mucosa may increase late
cancer risk. Annual endoscopic follow-up of pouches is recommended. All
polyps or suspicious lesions should be biopsied, excised or destroyed, preserving a sample for histology. After ileorectal anastomosis,
cancer risk in the rectal stump increases with chronological age, with risk ranging from 5-10% at age 50 years, to 14-29% at age 60 years. Surveillance of the rectal stump in FAP is recommended every 4-6 months. There may be a role for
prostaglandin synthesis inhibitors in some patients.