The sigmoid colon ( pelvic colon ; sigmoid flexure ) forms a loop that averages about 40 cm. in length , and normally lies within the pelvis , but on account of its freedom of movement it is liable to be displaced into the abdominal cavity .
The sigmoid colon ( pelvic colon ; sigmoid flexure ) is the part of the large intestine that is closest to the rectum and anus . 
 It forms a loop that averages about 40 cm. in length , and normally lies within the pelvis , but on account of its freedom of movement it is liable to be displaced into the abdominal cavity .