Non-refluxing Primary Megaureter in Children Resolves From Proximal to Distal

To evaluate a population of children with non-refluxing primary megaureter (NRPM), we investigated spontaneous resolution of ureteral dilation and the pattern (proximal to distal or distal to proximal) in which it occurs.

From our prospectively collected prenatal hydronephrosis (HN) database (0-24 months, 2008-2017), selecting those with NRPM (n = 92). We excluded patients who underwent surgery (n = 20), children with <6 months follow-up (n = 2) and without a voiding cystourethrogram (VCUG) (n = 4). Images were segregated into 198 ureteric segments (proximal/mid/distal). We defined resolution as Society for Fetal Urology (SFU) (0/1), anteroposterior diameter (APD) <10 mm, and ureteric dilatation <5 mm. Descriptive statistics and Kaplan-Meier curves were created for time-to-resolution analyses.

Of 66 patients and 198 ureteral segments, median age at presentation was 2 months (0-12), 83% were male (33% circumcised). Mean APD at baseline was 11 ± 4 mm, and 79% had (SFU 3/4) HN. Mean dilatation of ureteral segments (mm) at baseline was: 9 ± 2 proximal, 9 ± 2 mid, and 11 ± 3 distal. At a median follow-up time of 26 (7-83) months, dilation of 55 (83%) proximal, 48 (72%) mid, and 22 (33%) distal ureteric segments had resolved. Overall, HN resolution occurred in 76% of patients. Resolution rates were similar for proximal/mid-ureters (83% vs 72%; P = .20); however, they were significantly different from distal segments (83% proximal vs 33% distal; 72% mid vs 33% distal, P <.01).

Our data suggest that spontaneous resolution of NRPM follows a proximal to distal progression. Distal ureteric dilatation takes up to 10 months longer to resolve compared to that of proximal and mid-ureteric segments, as well as that of the renal pelvis.