Hemodynamics of the inferior mesenteric arterial circulation.

The purpose of this study was to determine the significance of collateral supply from the hypogastric arteries (HGAs) to the inferior mesenteric arterial (IMA) bed. Peak systolic "stump" IMA and radial arterial pressures were obtained before and after clamping the right HGA, the left HGA, both HGAs, the middle colic artery (MCA) only, or the MCA plus right HGA, MCA plus left HGA, and MCA plus both HGAs in patients with aortoiliac aneurysm or occlusive disease. Six patients (four with aneurysms and two with occlusive disease) had patent IMAs. Five patients (four with aneurysms and one with occlusive disease) had chronically occluded IMAs. In the six patients with patent IMAs, clamping of the HGAs decreased the IMA-stump pressure index (IMA-SPI) from 0.61 +/- 0.20 to 0.56 +/- 0.17, 0.54 +/- 0.17, and 0.54 +/- 0.19, respectively (p greater than 0.05) whereas clamping only the MCA decreased the IMA-SPI from 0.61 +/- 0.20 to 0.32 +/- 0.15 (p less than 0.01). In the five patients with chronically occluded IMAs, clamping of the HGAs decreased the IMA-SPI from 0.60 +/- 0.11 to 0.59 +/- 0.12, 0.58 +/- 0.12, and 0.57 +/- 0.11, respectively (p greater than 0.05), whereas clamping the MCA decreased the IMA-SPI from 0.60 +/- 0.11 to 0.34 +/- 0.04 (p less than 0.01). These data suggest that branches of the superior mesenteric artery provide the major collateral pathway to the IMA bed and that the contribution through branches of the HGAs is insignificant in the acute setting.