Ultrasound evaluation of the Cesarean scar: relation between a niche and postmenstrual spotting.

Objective To evaluate the relationship between a niche and abnormal uterine bleeding, and to develop a sonographic classification of niches and evaluate its relationship to abnormal uterine bleeding. Methods An observational prospective cohort study was performed between October 2007 and May 2009. All women who had a Cesarean section performed in our hospital were asked to participate. Two hundred and twenty-five women were included and examined with both transvaginal sonography (TVS) and gel instillation sonohysterography (GIS) 6-12 months after the Cesarean section. In case of a niche, the depth, volume and residual myometrium were measured, and the shape was assessed according to a specified classification. A questionnaire and pictorial blood loss assessment chart were filled in. Results The prevalence of a niche on evaluation with TVS and GIS was 24.0% and 56.0%, respectively. A niche was considered to be present if the depth was at least 1 mm visualized with GIS. Postmenstrual spotting was reported by 33.6% of women with a niche and 15.2% of women without a niche (P = 0.002). The niche volume was significantly different between women with and without postmenstrual spotting (P = 0.02). Most niches had a semicircular (50.4%) or triangular shape (31.6%). No significant relationship was identified between the shape of the niche and postmenstrual spotting (P = 0.19). Conclusions A niche is present in 56.0% of women with a history of Cesarean section when examined by GIS and is associated with postmenstrual spotting. Semicircular and triangular niches are most common, but the shape is not related to postmenstrual spotting. Copyright (C) 2010 ISUOG. Published by John Wiley & Sons, Ltd.