Background:

Primary non-refluxing megaureter (PNM) comprises 10-20% of prenatal hydronephrosis cases. There is limited information on the rates and predictors for resolution of upper tract dilatation. Here, we aim to evaluate the time to detected resolution of hydroureteronephrosis during monitoring and assess early predictors for spontaneous resolution.

Methods:

We defined PNM as hydroureteronephrosis with ureteral dilatation > 7mm and excluded patients with other etiologies for upper tract dilatation. Resolution was defined as: < 10 mm anteroposterior diameter of the renal pelvis, < 8 mm ureteral dilatation, or SFU grade <= 2. Patients were censored if they underwent surgical intervention or were lost-to-follow-up before documenting spontaneous resolution. Kaplan-Meier curves were drawn to illustrate the cumulative rate of resolution and determine univariate associations. Cox proportional hazards regression was performed to determine predictors for early resolution.

Results:

A total of 195 patients with PNM were identified within the study period, including 154 (84%) boys, with 71 (46%) of them circumcised. The median follow-up time was 29 months (IQR 13, 51), with 121 (62%) achieving sonographic resolution during scheduled monitoring without intervention. The median age when resolution was documented was 11 months (IQR 5, 20). On survival analysis (Figure 1), initial low grade hydronephrosis (HR 1.79, 95%CI 1.22, 2.64, p = 0.001), initial anteroposterior diameter ≤ 15 mm (HR 2.60, 95%CI 1.74, 3.88, p < 0.001), lack of ureteral tortuosity (HR 1.84, 95%CI 1.27, 2.68, p = 0.003), and initial ureteral diameter ≤ 10 mm (HR 1.93, 95%CI 1.35, 2.76, p < 0.001) were associated with increased likelihood of spontaneous resolution. On Cox multivariate regression, larger anteroposterior diameter (HR 0.53, 95%CI 0.29, 0.95, p = 0.03) and larger ureteral diameter (HR 0.66, 95%CI 0.44, 0.99, p = 0.04) were associated with delayed spontaneous resolution. However, high grade hydronephrosis (HR 0.76, 95%CI 0.51, 1.14, p = 0.18) and ureteral tortuosity (HR 0.78, 95%CI 0.48, 1.28, p = 0.32) were not independently associated with delayed spontaneous resolution.

Conclusion:

Early sonographic features in PNM are associated with the likelihood of spontaneous resolution, and greater anteroposterior and ureteral diameter are predictive of delayed spontaneous resolution of hydroureteronephrosis.