Predictive Factors for Spontaneous Resolution in Primary Obstructive Megaureter: The Impact of Hydronephrosis Severity on Clinical Outcomes

<b>Background/Objectives:</b> Primary obstructive megaureter (POM) is a rare congenital urological condition usually diagnosed prenatally or in early childhood. Conservative management is increasingly preferred due to a high potential for spontaneous resolution. However, reliable predictors of spontaneous resolution remain controversial, complicating clinical decision-making. This study aimed to identify the demographic, clinical, and imaging parameters predictive of spontaneous resolution in patients with primary obstructive megaureter. <b>Methods:</b> We retrospectively analyzed 21 pediatric patients diagnosed with primary obstructive megaureter, who were treated conservatively at the Maria Sklodowska Curie Emergency Clinical Hospital for Children from January 2015 to December 2024. Clinical parameters, imaging findings, and renal function were evaluated. Statistical analyses included univariate comparisons and multivariate logistic regression modeling. <b>Results:</b> Spontaneous resolution occurred in 12 (57%) patients, at a median age of 45.75 months. The only statistically significant predictor identified was the initial hydronephrosis grade (<i>p</i> = 0.046). Patients with mild-to-moderate dilation (Grades I-II) had a significantly higher resolution rate (11 of 15 cases) compared with those with severe dilation (1 of 6 cases). Ureteral diameter showed a trend toward predicting outcomes, with unresolved cases having larger median diameters (15 mm vs. 10.5 mm, <i>p</i> ≈ 0.08). Age at diagnosis, sex, bilateral involvement, and history of urinary infections did not significantly influence resolution rates. <b>Conclusions:</b> The initial severity of hydronephrosis significantly predicts spontaneous resolution in primary obstructive megaureter. Conservative management is particularly justified in mild-to-moderate cases, whereas patients with severe dilation may require early intervention due to lower resolution likelihood.