Figure 1

Sketch of anatomic regions of the rectum. The X-axis position on the rectal wall on four different scales: radial degrees, clock face position, quadrant, and radians. The Y-axis represents distance from the dentate line in centimeters. Note that the boundary of the peritoneal reflection feature is represented by a sine wave, and boundaries of other common features as well as the limit of the rectoscope are represented by straight lines.