PERSISTENT POLYURIA AFTER POSTERIOR URETHRAL VALVES

Objective To assess urinary concentrating ability, urine production and glomerular filtration rates in a cohort of boys with previously treated posterior urethral valves. Patients and methods Urinary concentrating capacity was assessed in 51 boys aged 5.4-9.9 years with previously treated posterior urethral valves. They all completed urinary frequency/volume charts, permitting calculation of 24 h urine volumes. The osmolality of an overnight urine collection was measured and, if <800 mOsm/kg (n=40), an intramuscular injection of desamino-cys-1-8-D-arginine vasopressin was given to determine the maximum concentrating ability. The glomerular filtration rate (GFR) was estimated from the plasma clearance of Cr-51- ethylenediamine tetra-acetic acid following a single intravenous injection. Results The mean 24 h urine volume was 1025+/-448 (so) mt. The mean overnight urine flow rate was 28.4+/-17.9 mL/h. Urinary concentrating capacity was impaired (<800 mOsm/kg) in 30 (59%) of the boys and <300 mOsm/kg in eight (16%). The mean GFR was 81+/-38 ml/min/1.73 m(2) SA. Significant correlations were noted between the GFR, the maximum urine concentration and the 24 h urine volume. Conclusion Persistent polyuria after valve ablation occurs in boys with posterior urethral valves. This has implications both in terms of urinary continence and on-going renal impairment.