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

Purpose: We describe and develop predictors for spontaneous resolution of primary obstructive megaureter (POM) from early ultrasound (US) measures.

Materials and methods: 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.

Results: 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.

Conclusions: 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.