When the marginal artery is not marginal.

In the course of dissection one does not normally pay much attention to the anastomosing loops forming the marginal artery. The observation of a significant precolic anastomosing loop on the descending colon of a spare subject came as quite a surprise. The same was noted on a second subject, an obese male with sagging abdomen and, to a lesser degree, on a third. Such an occurrence would have surgical significance, if only because the evaluation of the blood supply to the segment of bowel that was to be resected would be much more difficult. In addition, the blood supply to the distal bowel could be impaired following resection, depending upon the collateral circulation.