Integrating residual myometrial thickness and Adler vascularity index to predict suction curettage outcomes in cesarean scar pregnancy: A retrospective cohort study

OBJECTIVE: This study identifies quantitative ultrasound predictors for the failure of ultrasound-guided suction curettage (USG-SC) in cesarean scar pregnancy (CSP) and develops a risk stratification model integrating residual myometrial thickness (RMT) and local vascularity (Adler grade). METHODS: This retrospective cohort study included 415 patients with CSP who underwent primary USG-SC. Baseline morphological categorization adhered to the international Delphi consensus. Procedural failure was defined as hemorrhage (≥500 mL), requirement for secondary interventions, or incomplete evacuation. Preoperative sonographic parameters, primarily RMT and Adler vascularity grading, were evaluated. Multivariate logistic regression and receiver operating characteristic analyses were used to ascertain independent predictors and evaluate model performance. RESULTS: The overall failure rate was 13.7% (57/415). Compared to the successful group, the failed group presented with a significantly thinner RMT (1.6 ± 0.7 mm vs. 3.4 ± 1.2 mm; P < 0.001) and a higher prevalence of Adler grade 3 vascularity (P < 0.001). Multivariate analysis confirmed RMT as a significant independent protective factor (adjusted odds ratio OR = 0.21, 95% CI: 0.12-0.38) and Adler grade 3 vascularity as a significant risk factor (adjusted OR = 4.52, 95% CI: 1.85-11.04). The optimal RMT cut-off for predicting failure was determined to be 2.2 mm (area under the curve AUC = 0.912). The incorporation of RMT and Doppler vascularity into a combined algorithm yielded the highest predictive performance (AUC = 0.945). CONCLUSION: Integrating RMT with Color Doppler vascularity establishes a robust quantitative framework for surgical triage in cesarean scar pregnancy. Specifically, an RMT ≥2.2 mm accompanied by low-to-moderate vascularity (Adler grades 0-2) reliably identifies optimal candidates for primary USG-SC. This combined approach minimizes hemorrhagic morbidities while safely averting unnecessary prophylactic interventions.