How long is the five centimeter margin?

Five centimeters is often taught to be the minimal safe margin of resection distal to a colonic or rectal tumor. The actual time at which this margin is measured can greatly alter the recorded length. We studied the length of the distal margin in ten patients who underwent colonic resection. Depending upon the time that it was measured, a margin of 5.0 centimeters, unstretched in situ, was noted to shrink to as little as 1.9 centimeters. Studies which have advocated a shorter margin distal to carcinoma of the colon and rectum, which do not define the time at which the margin was measured, could give a surgeon inappropriate confidence in an inadequate tumor margin.