Postpartum evaluation of the anal sphincter by transperineal three-dimensional ultrasound in primiparous women after vaginal delivery and following surgical repair of third-degree tears by the overlapping technique.

OBJECTIVE: Intrapartum damage to the anal sphincter is an important factor in fecal incontinence. Recognized lacerations occur in 0.36-8.4% of vaginal deliveries, and occult sphincter damage in up to 35% of primiparous women. We examined the role of three-dimensional transperineal ultrasound (3DTUS) in the evaluation of the anal sphincter in primiparous women after vaginal delivery and after surgical repair of third-degree intrapartum tears by the overlapping technique.
METHODS: During 2004-2005 139 primiparous women without clinically recognized third- to fourth-degree anal sphincter tears were prospectively studied 24-72 h postpartum (Group 1) and 13 primiparous women were examined 48 h to 4 months following surgical repair of third-degree tears with the overlapping technique (Group 2). A 3D 5-9-MHz transvaginal probe was placed in the area of the fourchette and perineal body in transverse and sagittal planes and 2-4 volumes were stored. The parameters studied were: examination duration; continuity of the internal and external sphincters; occult sphincter damage; internal sphincter and external sphincter width-measured 1.5 cm from the distal margin of the anus-at the '12, 3, 6 and 9 o'clock positions'; length of the posterior internal sphincter.
RESULTS: Scanning was possible in all women and the stored volumes were adequate in 127/139 (91.4%) cases. Mean examination time was 3.5 min. In Group 1, occult sphincter defect was suspected in 10/127 women (7.9%). These patients were excluded from measurement calculations, leaving 117 cases for analysis. The internal sphincter was consistently visualized in all the remaining patients (n = 117), while the external sphincter was fully visualized in 99/117 women (84.6%), and partially visualized in the remainder. Mean internal sphincter thickness was 2.60, 2.55, 2.60 and 2.72 mm at the 12, 3, 6 and 9 o'clock positions, respectively, and mean internal sphincter length was 3.34 cm. Mean external sphincter thickness was 4.15, 4.20, 4.21 and 4.20 mm at the 12, 3, 6 and 9 o'clock measurement points. In Group 2, 3DTUS confirmed anatomic abnormalities in all the women in the area surrounding the 12 o'clock position. Evaluation of sphincter tears and their position and length was possible using the longitudinal view. Thinning of the internal sphincter in the area of damage and thickening on the opposite side, the 'half moon sign', sphincter discontinuity, thickening of the external sphincter in the area of repair and abnormality of mucous folds, seemed to be common signs of third-degree intrapartum sphincter tears, even after repair.
CONCLUSIONS: 3DTUS is an accessible and promising method for postpartum sphincter evaluation, that is apparently well tolerated by patients. Reference data for sphincter anatomy representative of findings at transperineal ultrasound in primiparous women in the postpartum period have been established. Copyright 2007 ISUOG. Published by John Wiley & Sons, Ltd.