Functional outcomes after pyeloplasty in solitary kidneys: structured analysis with the implication of Acute Kidney Injury Network (AKIN) staging criteria to predict long-term renal function recoverability

Objectives: To assess the long-term functional outcomes after pyeloplasty in solitary kidney (SK) models and to define factors affecting postoperative renal function recoverability in adults.

Patients and methods: We retrospectively evaluated all adult patients who underwent pyeloplasty for pelvi-ureteric junction obstruction (PUJO) in SK. Long-term renal function was assessed by diuretic scintigraphy and morphological changes were also determined, e.g. renal parenchymal volume (RPV) and parenchymal thickness (PT). We considered a >20% increase in glomerular filtration rate (GFR) as improvement, >20% decrease as deterioration, and changes within 20% as stationary renal function. Univariate and multivariate analysis for factors affecting renal function recoverability, including the Acute Kidney Injury Network (AKIN) Staging System postoperatively, were performed.

Results: The study included 62 patients with a mean (SD) age of 29 (10.5) years. At a median of 48 months, the mean (SD) GFR increased from 41.3 (17) to 48.5 (20.1) mL/min (P < 0.001), with a significant increase in RPV and PT (P = 0.02 and P = 0.001, respectively). Follow-up renal function was static, improved and decreased in 39 (63.4%), 17 (27%) and six (9.6%) patients, respectively. Functional success was achieved in 90.4%. Patient's age ≥39 years, PT ≤0.75 cm and higher early postoperative AKIN staging were predictors associated with a 4.8-, 3.2- and 2.7-fold deterioration in renal function.

Conclusion: Pyeloplasty in SK preserved renal function in 90.4% of the present patients. Pyeloplasty in SK when associated with older age, decreased PT preoperatively, and early higher AKIN staging postoperatively was associated with poor renal function recoverability.