A 70-year-old man develops sudden left-sided abdominal pain and bloody diarrhoea two days after an episode of atrial fibrillation with hypotension. Colonoscopy shows oedematous, dusky mucosa with subepithelial haemorrhage in the region of the splenic flexure, but no necrotic mucosa. Which feature of colonic blood supply explains this distribution?

• A The caecum has the poorest collateral supply in the colon
• B The ascending colon is supplied solely by the inferior mesenteric artery
• C The splenic flexure lies in a watershed zone between the superior and inferior mesenteric arteries ✓
• D The rectum depends entirely on the middle rectal artery

Explanation

Ischaemic colitis characteristically affects watershed areas with limited collateral circulation: the splenic flexure (Griffiths point) between SMA and IMA territories, and the rectosigmoid junction (Sudeck point). The caecum can be affected in low flow states but is not the classic site, and the rectum is rarely involved because of its rich dual supply from inferior mesenteric and internal iliac arterial branches. Non-necrotic mucosa allows conservative management with bowel rest and fluids.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.