Blood pressure changes in the marginal artery of the colon following occlusion of the inferior mesenteric artery.

The perfusion pressure in the marginal artery of the descending colon was measured continuously at laparotomy in eight patients and the effect of sudden occlusion of the inferior mesenteric artery recorded. Three patients with ulcerative colitis, all in their early 30s, and five elderly patients with colonic or rectal carcinoma were studied. In all patients occlusion caused an initial and marked pressure drop, which remained reduced at a critically low level in two of the elderly patients. Such a reduction in perfusion pressure is probably still insufficient to interfere with the nourishment of the terminal part of the colon provided that the systemic pressure is kept at a normal level. However, since in many patients there is a sharp drop in systemic blood pressure during the recovery phase after surgery, it appears likely that the perfusion pressure in the marginal artery may in those cases be insufficient to maintain an adequate blood flow to the colon despite the inherent tendency of "auto-regulation" in this vascular bed. The results of the present study indicate that, contrary to previous belief, ligation of the inferior mesenteric artery may increase the risk of ischaemia in the terminal part of the descending colon, leading to anastomotic dehiscence after anterior resection, or sloughing after a "pull-through" operation. This complication could probably be prevented by a more generous resection of the sigmoid and descending colon, thus reducing the length of the anastomosis formed by the arc of Riolan and by careful maintenance of an adequate blood pressure during the recovery phase.