Renal Tubular Functions in Patients with Posterior Urethral Valve

Abstract

Objectives: The aim of this study was to evaluate tubular functions of posterior urethral valve patients with preserved glomerular functions. Methods: A total of 25 children (ages 1 - 18) who underwent surgery for PUV and had an estimated glomerular filtration rate ≥ 90 mL/min per 1.73 m2 on long term follow-up and age-matched 25 healthy controls were enrolled. Blood and urine samples were collected to assess electrolyte reabsorption, proteinuria, enzymuria, urine acidification and concentration. Results: Even though microalbumin/creatinine ratio was higher in the patient group [1.00 (1.98) vs 0.31 (0.34) mg/gr creatinine, P = 0.005] none of the subjects had enzymuria, overt proteinuria or hyperphosphaturia. Serum bicarbonate levels were lower and urinary pH higher in patients than the controls (23.2 ± 2.1 vs. 24.6 ± 1.9 mmol/L, P = 0.028 and 6.24 ± 0.77 vs. 5.60 ± 0.64, P = 0.004); furthermore, patients had lower urinary osmolality and density (525 ± 214 vs. 743 ± 194 mOsm/L, P = 0.001 and 1011 ± 5.0 vs. 1016 ± 6.8, P = 0.005). When patients were compared among themselves according to presence or absence of renal scarring and when patients without renal scars were compared to healthy controls, similar findings persisted. Conclusions: This study showed that during long-term follow-up of posterior urethral valve patients with normal glomerular filtration rates, even though proximal tubular functions do not seem to be impaired, acidification and concentration defects exist indicating distal tubulopathy.