0-6 months versus 6-12 months laparoscopic pyeloplasty in infants: impact on short-term renal ultrasonographic parameters.

OBJECTIVE: To compare postoperative recovery outcomes between infants undergoing laparoscopic pyeloplasty (LP) for unilateral ureteropelvic junction obstruction (UPJO) at 0-6 months versus 6-12 months of age, and to identify whether surgical timing differentially affects longitudinal trajectories of renal ultrasound parameters. METHODS: This retrospective cohort study included 58 infants with unilateral UPJO who underwent laparoscopic dismembered pyeloplasty between March 2021 and February 2026. Patients were stratified into 0-6 months (n = 34) and 6-12 months (n = 24) groups. Linear mixed-effects models with random intercepts for patient were fitted to analyze longitudinal recovery trajectories of renal ultrasound parameters (anterior-posterior pelvic diameter [APD], hydronephrosis-to-parenchymal area ratio [HPAR], parenchymal thickness [PT], and minimal parenchymal thickness [MPT]), adjusting for baseline value and surgical indications. RESULTS: The 0-6 months group presented with more severe preoperative hydronephrosis (APD: 33.0 vs. 24.5 mm, P = 0.002; HPAR: 1.11 vs. 0.75, P = 0.009; MPT: 2.38 vs. 3.00 mm, P = 0.015). Both groups showed postoperative improvements in all parameters. Percentage improvement in MPT was greater in the 0-6 months group (1.74 ± 1.40 vs. 0.96 ± 0.77, P = 0.008). Mixed-effects models revealed that only MPT demonstrated a significantly steeper recovery slope in the 0-6 months group (interaction: β = - 0.0015, SE = 0.0006, P = 0.012), whereas APD, HPAR, and PT showed comparable slopes between groups. CONCLUSION: LP performed at 0-6 months was associated with superior MPT recovery dynamics compared with surgery at 6-12 months, suggesting that earlier intervention may be associated with more favorable MPT recovery dynamics in UPJO.