You are treating a 78-year-old man for recent onset of diarrhea, tenesmus, and minor bleeding...

Radiation proctitis is a well-known complication of pelvic radiation therapy (e.g., for prostate cancer). It presents months to years after treatment with rectal bleeding, tenesmus, and mucosal ulceration on colonoscopy.

Toronto Notes 2023 – Gastroenterology, “Radiation-Induced GI Injury”:

“Radiation proctitis presents with rectal bleeding, tenesmus, urgency. Colonoscopy shows pale, friable mucosa, ulcerations, and telangiectasia.”

MCCQE1 Objectives (Gastroenterology > 47-2: GI Bleeding and Complications):

“Candidates must recognize radiation proctitis based on history of radiation and characteristic endoscopic findings.”

Ulcerative colitis (B) usually starts younger and is more diffuse. Diverticulosis (C) affects the left colon and causes painless bleeding. Recurrent prostate cancer (D) and rectal cancer (E) would show mass or infiltration.