A 68-year-old man with atrial fibrillation develops sudden left-sided abdominal pain and bloody diarrhoea. CT shows thickening of the bowel wall at the splenic flexure with normal distal colon. Which feature best explains this site of involvement?

• A It is the segment with the greatest bacterial load
• B It is the narrowest part of the colon, predisposing to stasis
• C It has the thickest muscularis propria, increasing oxygen demand
• D It lies at a watershed between the superior and inferior mesenteric arterial territories ✓

Explanation

The splenic flexure is supplied by the terminal branches of both the superior mesenteric artery via the middle colic and the inferior mesenteric artery via the ascending branch of the left colic. This watershed zone has poor collateral circulation, making it vulnerable to ischaemia during low-flow states such as atrial fibrillation with hypoperfusion. Bacterial load and wall thickness are uniform concerns across the colon and do not explain focal susceptibility.

Reference: Sabiston Textbook of Surgery, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.