Ultrasound pattern of upper urinary tract remodeling after pyeloplasty: a prospective multicentric study

Ureteropelvic junction obstruction can cause significant changes in the upper urinary tract (UUT). Although pyeloplasty may successfully restore normal flow through the UPJ, those modifications do not resolve immediately and may persist. We aimed to characterize the sonographic remodeling pattern of the UUT following successful pyeloplasty.

Prospective multicenter study, including pediatric patients status post-pyeloplasty (2021-2022) with standardized US assessments at 2, 6 and 9 months, 1 and 2 years after double J stent removal. The primary outcome was the percentage reduction in anteroposterior diameter (APD) of the renal pelvis compared to baseline.

31 patients, median age at surgery was 6.5 months (IQR 6.5-105.5). Median preoperative APD was 24 mm (21-31 mm), with median reductions of 30% at 2 months, 60% at 6 months, 64.5% and 71.4% (40.9-82.5%) at 1 and 2 years. Median cortical thickness on the operated side improved from 4.9 mm (3.3-5.5 mm) to 8 mm at 2 years (63% increase). Median renal lengths were 72 mm (55-123 mm) on the operated side and 60 mm (50-120 mm) on the unaffected side at baseline, increasing to 88 mm (62-138 mm) and 76 mm (60-120 mm) respectively at 2 years.

The UUT undergoes progressive and measurable remodeling on US following pyeloplasty. Most cases show a 30% APD reduction within the first 2 months and 60% by 6 months, with minimal changes thereafter. Cortical thickness also progressively improves but typically does not reach normal values.