A Prospective Study of the Incidence and Characteristics of Post-Obstructive Diuresis Following Pyeloplasty for Unilateral Pelvi-Ureteric Junction Obstruction

Abstract

Objectives: To study the characteristics of urine production and post-obstructive diuresis (POD) following pyeloplasty for unilateral pelvi-ureteric junction obstruction (PUJO) in children and identify risk factors for the development of significant POD.

Methods: A prospective observational study was conducted on pediatric patients undergoing pyeloplasty for unilateral PUJO. Post-operative urine output was measured from the affected kidney via nephrostomy catheter placed during surgery and from the opposite normal kidney via per-urethral catheter. Biochemical analysis of the urine sample was performed. Patients were divided into 2 groups: Group-1 with POD (total urine output (UO) >4 mL/kg/hour) (n = 19; 63.33%), and Group-2 (without POD) (n = 11; 36.66%). Preoperative imaging findings were analyzed in the 2 groups which may indicate risk for POD. Hydration was maintained in all patients with POD and remained stable with appropriate oral replacement.

Results: Post-obstructive diuresis occurred in Group-1 patients within 48 hours after surgery and resolved by postoperative day 5. They had statistically significant lower median renal parenchymal thickness and higher median renal pelvis antero-posterior diameter (APD), differential ratio of kidney size and proportion of grade-4 hydronephrosis (HN) than Group-2 patients. Urine from the affected kidney had significantly higher mean UO, pH, fractional excretion of sodium (FeNa+), potassium (FeK+), magnesium (FeMg+) and lower specific gravity, creatinine clearance, (phosphorus) FePO4 than urine from the normal kidney.

Conclusion: Post-obstructive diuresis occurring in children with pyeloplasty for unilateral PUJO is usually well tolerated by maintaining hydration. Patients with larger kidneys, more severe HN, higher pelvis APD, and parenchymal thinning are at a significantly higher risk.

Cite this article as: Pokharkar AD, Meshram RB, Yadav C, et al. A prospective study of the incidence and characteristics of post-obstructive diuresis following pyeloplasty for unilateral pelvi-ureteric junction obstruction. Urol Res Pract. 2025;51(6): 242-247.