A patient with familial adenomatous polyposis (FAP) is undergoing risk reduction surgery. Compared to total proctocolectomy with ileal pouch-anal anastomosis (IPAA), restorative proctocolectomy with IPAA is preferred because FAP patients harbour a particular risk in the retained rectal stump. What is the approximate lifetime risk of developing rectal cancer in an FAP patient with an intact retained rectum?

• A ~10% lifetime risk
• B ~30% lifetime risk
• C ~5% lifetime risk
• D ~60% lifetime risk ✓

Explanation

In FAP patients who undergo subtotal colectomy with ileorectal anastomosis (IRA) rather than total proctocolectomy, the retained rectum carries approximately a 25–60% lifetime risk of developing carcinoma, with many series quoting around 60% by age 60. This is why restorative proctocolectomy with IPAA (removing the entire rectum) is preferred for FAP when technically feasible. Regular surveillance endoscopy of the rectal remnant is mandatory if IRA is performed.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.