The sigmoid colon is 10 to 15 in. (25 to 38 cm) long and begins as a continuation of the descending colon in front of the pelvic brim. Below, it becomes continuous with the rectum in front of the 3rd sacral vertebra.
The sigmoid colon is mobile and hangs down into the pelvic cavity in the form of a loop. This sigmoid colon is attached to the posterior pelvic wall by the fan-shaped sigmoid mesocolon.