Sigmoidocele (also known as pouch of Douglas descent) is a medical condition in which a herniation of peritoneum containing loops of redundant sigmoid colon descends (prolapses) into the rectouterine pouch (in females), between the rectum and the vagina. This can obstruct the rectum and cause obstructed defecation syndrome.

Sigmoidocele may be internal if it is only detectable on defecography, or external if it detectable without imaging and associated with a rectocele or rectal prolapse. It is a type of posterior compartment prolapse.

Sigmoidocele may be classified according to size relative to the pubococcygeal line.

The severity of sigmoidocele can be described with reference to the position of the lowest loop of the sigmoid relative to lines drawn on defecography:

Sigmoidocele may not cause any symptoms.

The phenomenon is caused by a weak section of fascial supports of the vagina (the uterosacral cardinal ligament complex and rectal vaginal septum), which allows a section of peritoneum containing the sigmoid colon to prolapse out of normal position and descend between the rectum and the vagina.

The mesentery of the sigmoid colon (the structure which attaches the colon to the abdominal wall) is termed the mesosigmoid. This structure is very flexible, which means that the sigmoid colon is very mobile and may change position. During defecation it may be pushed down, eventually causing sigmoidocele.

Sigmoidocele may be associated with descending perineum syndrome.