This study describes the anatomy of the rectovaginal pouch, the sigmoid colon, and rectum in women with posterior enterocele and anterior rectal wall procidentia. The anatomy of rectovaginal pouch, sigmoid colon, and rectum was described in 36 women with an enterocele (group A) and compared with those of 43 women (group B) without pelvic organ prolapse. Women with previous incontinence or prolapse surgery were excluded. The mean age in group A was 58 years (40-75) and in group B 35 years (19-64; P < 0.001). There were 15 nulliparas in group B. Nine women in group A had an internal anterior rectal wall procidentia, and one woman had an external anterior rectal wall procidentia. In group A, the rectovaginal pouch was significantly deeper, the sigmoid mesocolon at S1 shorter and showed more often a straight course (P < 0.05). These characteristics (termed "grande fosse pelvienne") were present in 23 women (64%) in group A and in 6 (14%) in group B, three of the latter were young nulliparas (P < 0.001). Age, parity, menopausal status, body mass index, constipation, and varicose veins were not associated with a grande fosse pelvienne. The typical anatomy in women with an enterocele and anterior rectal wall procidentia was a sigmoid colon with a straight course and a short mesentery at S1 and a rectovaginal pouch that covered more than half of the vaginal length. It may be a congenital condition and important in the development of an enterocele and rectal wall procidentia.