Comparative diagnostic performance of three dimensional transvaginal sonography and three dimensional saline infusion sonohysterography for cesarean scar defects

Cesarean scar defects (CSDs) are disruptions in the myometrium at the site of a previous cesarean delivery and have become a concern in reproductive medicine due to their impact on gynecological and reproductive health. This cross-sectional study compared the diagnostic performance of three-dimensional transvaginal sonography (3D-TVS) and three-dimensional saline infusion sonohysterography (3D-SIS) in detecting CSDs among 403 women with prior cesarean delivery. The primary outcome was the prevalence of CSDs detected by 3D-TVS and 3D-SIS. Secondary outcomes included diagnostic agreement and the correlation of morphological parameters including defect length, width, residual myometrial thickness (RMT), and adjacent myometrial thickness (AMT). CSD prevalence was 34.0% by 3D-TVS and 80.6% by 3D-SIS, demonstrating poor agreement (κ = 0.20). Sensitivity and specificity of 3D-TVS were 42.15 and 100%, respectively. Measurements from both modalities were positively correlated ( p < 0.0001), showing strong correlation for RMT ( r = 0.60) and moderate correlations for defect length ( r = 0.47), width ( r = 0.57), and AMT ( r = 0.49). These findings support a streamlined diagnostic approach: when CSD is detected by 3D-TVS, further 3D-SIS evaluation is likely unnecessary, whereas a negative 3D-TVS finding in symptomatic patients may warrant subsequent 3D-SIS assessment to reduce the risk of missed diagnoses.