Cesarean section scar evaluation by saline contrast sonohysterography

To investigate the frequency of images suggesting the existence of a dehiscence at the site of the uterine scar after Cesarean section.

Thirty-three women with a past history of Cesarean section who were planning a further pregnancy were involved in the study. Saline contrast sonohysterography (SCSH) was performed a minimum of 3 months following Cesarean section. The thickness of the residual myometrium, the thickness of the myometrium bordering the scar and the depth of the filling defect in the scar (i.e. the 'niche', defined as a triangular, anechoic area at the presumed site of incision) were recorded in each case. A 'dehiscence' was defined as a niche whose depth was at least 80% of the anterior myometrium.

In 19/33 (57.5%) patients a niche with a depth of 4.2 +/- 2.5 (range, 1.2-11.7) mm was identified. In these patients the residual myometrium measured 6.5 +/- 2.7 (range, 0-10.9) mm vs. 8.9 +/- 2.0 (range, 6.9-13.9) mm in the remaining 14 patients without a niche. Within the 19 niches, two dehiscences were identified.

Niches can be identified by SCSH following a Cesarean section in about 60% of patients. The prevalence of scar dehiscence (in the present series 2/33 or 6%) is much higher than the reported risk of uterine rupture (0.4%).