Lower gastrointestinal bleeding in the elderly: a rare aetiology masquerading as a diverticular bleed.

Bleeding per rectum is a relatively common acute surgical presentation. Common causes include diverticular disease, colitis, haemorrhoids, polyps, etc. An 83-year-old man with a history of recurrent rectosigmoid diverticulitis and bilateral internal iliac artery aneurysms for 2 years presented with rectal bleeding. He was suspected to have a diverticular bleed based on history and examination. A CT scan revealed a large haematoma adjacent to the right isolated internal iliac artery aneurysm (IIIAA) almost indistinguishable from the adjacent rectosigmoid, consistent with a ruptured IIIAA and an ileorectal fistula. The fistula was of a primary vascular enteric type and was accentuated by the inflammation arising from the diverticulitis. Hence, presence of more common or apparently obvious causes should not deter clinicians from thoroughly investigating the case. Rare causes should be kept in mind while dealing with common acute presentations, especially in elderly patients with multiple comorbidities.