Most common site of ischemia of large bowel is at

(A) Splenic flexure [B&L26-11831# Colon receives blood from both the superior and inferior mesenteric arteries.> Blood supply from these two major arteries overlap, with abundant collateral circulation via the marginal artery of the colon.> However, there are weak points, or "watershed" areas, at the borders of the territory supplied by each of these arteries, such as the splenic flexure and the transverse portion of the colon.> These watershed areas are most vulnerable to ischemia when blood flow decreases, as they have the fewest vascular collate ra\s.> Rectum receives blood from both the inferior mesenteric artery and the internal iliac artery; the rectum is rarely involved by colonic ischemia due to this dual blood supply.