Ultrasound evaluation of the posterior pelvic compartment

The posterior pelvic compartment, defined as consisting primarily of the rectosigmoid colon and peritoneal-lined cul-de-sac, was evaluated in 104 patients. Tumors and pseudotumors (fluid- and feces-filled loops of bowel) were ultrasonographically analyzed according to: (a) morphology and echo characteristics, and (b) location within either the cul-de-sac or rectosigmoid colon. On routine examination, a striking similarity between pathological processes and pseudotumors was demonstrated; these were diagnosed correctly only by the use of a technique in which the rectosigmoid colon is filled with water. Combined distension of the urinary bladder and rectosigmoid colon also enabled localization and differentiation of abnormalities within the cul-de-sac.