Posterior compartment prolapse on two-dimensional and three-dimensional pelvic floor ultrasound: the distinction between true rectocele, perineal hypermobility and enterocele.

OBJECTIVES Posterior compartment descent may encompass perineal hypermobility, isolated enterocele or a 'true' rectocele due to a rectovaginal septal defect. Our objective was to determine the prevalence of these conditions in a urogynecological population. METHODS One hundred and ninety-eight women were clinically evaluated for prolapse and examined by translabial ultrasound, supine and after voiding, using three-dimensional capable equipment with a 7-4-MHz volume transducer. Downwards displacement of rectocele or rectal ampulla was used to quantify posterior compartment prolapse. A rectovaginal septal defect was seen as a sharp discontinuity in the ventral anorectal muscularis. RESULTS Clinically, a rectocele was diagnosed in 112 (56%) cases. Rectovaginal septal defects were observed sonographically in 78 (39%) women. There was a highly significant relationship between ultrasound and clinical grading (P < 0.001). Of 112 clinical rectoceles, 63 (56%) cases showed a fascial defect, eight (7%) showed perineal hypermobility without fascial defect, and in three (3%) cases there was an isolated enterocele. In 38 (34%) cases, no sonographic abnormality was detected. Neither position of the ampulla nor presence, width or depth of defects correlated with vaginal parity. In contrast, age showed a weak association with rectal descent (r = -0.212, P = 0.003), the presence of fascial defects (P = 0.002) and their depth (P = 0.02). CONCLUSIONS Rectovaginal septal defects are readily identified on translabial ultrasound as a herniation of rectal wall and contents into the vagina. Approximately one-third of clinical rectoceles do not show a sonographic defect, and the presence of a defect is associated with age, not parity.