Spontaneous Resolution of Primary Obstructive Megaureter: Risk Stratification and Prediction Based on Early Sonographic Factors.

Abstract

We describe and develop predictors for spontaneous resolution of primary obstructive megaureter (POM) from early ultrasound (US) measures. Children referred to our institution between 2007 and 2023 for POM were reviewed. POM was defined as hydroureteronephrosis with ureteral dilation > 7 mm. We excluded patients with other etiologies for upper tract dilation. Resolution was defined as decrease in hydronephrosis to < 10 mm anteroposterior diameter (APD) or Society for Fetal Urology grade ≤ 2 or ≤ 7 mm in hydroureter. Patients were censored if they underwent surgical intervention or were lost to follow-up before documenting resolution. Kaplan-Meier curves were drawn to illustrate the cumulative resolution rate and determine univariate associations. Cox proportional hazards regression was performed to identify significant predictors for early resolution, and C index was calculated. A total of 159 patients were included, with a median index age of 2 months and a median follow-up of 30 months. Of these, 89 patients reached spontaneous resolution during monitoring, and likelihood of surgical indication at 1 year from US was 30%. APD > 15 mm, high-grade hydronephrosis, ureteral dilation > 10 mm, and ureter tortuosity at presentation were associated with a lower likelihood of resolution for individual Kaplan-Meier curves. A Cox regression model trained on these predictors achieved an adjusted C index of 0.68, and low APD remained associated with a higher likelihood of resolution. Early sonographic features in POM, specifically APD, are associated with the likelihood of spontaneous resolution. Patients with high-risk features at first US warrant closer follow-up.