The internal iliac arteries do not supply the inferior mesenteric artery

Abstract

Ischemic colitis can be prevented after surgical treatment for abdominal aortic aneurysm by routine or elective reconstruction of the inferior mesenteric artery (IMA) when this vessel is patent. Revascularization of at least one internal iliac artery (IIA) has been recommended when the IMA is occluded, although the validity of such reconstruction has never been substantiated. This study investigated the role of the IIAs in IMA hemodynamics: Do IIAs contribute significant collateral blood supply to the IMA bed in the treatment of abdominal aortic aneurysms? Between July 1990 and June 1992, 100 patients underwent elective aneurysmectomy. At least one IIA was routinely reconstructed whenever possible; 24 patients had 27 IIA revascularizations. When the IMA was patent (49 cases), the residual pressure in the inferior mesenteric artery (IMA stump pressure) and the pressure in the radial artery were measured before and during temporary occlusion of the IIAs. The inferior mesenteric indices (P) defined by the ratio of the IMA stump pressure (P_IMA) to the pressure in the radial artery (P_RAD) were calculated before (P1) and during (P2) clamping of the IIAs. The mean value of P1 was 0.64 ± 0.03 versus 0.63 ± 0.03 for P2 (P=NS). Adjustment of variations in P1 as a function of P2 by linear regression gave a straight line with a slope of less than 1. The IMA stump pressure is independent of whether vascular continuity of the IIAs is restored or whether these vessels are excluded. The IIAs do not contribute significant collateral blood supply to the IMA bed in treatment of abdominal aortic aneurysms.