Early Prognostic Value of Serum Creatinine Levels in Children With Posterior Urethral Valves

PURPOSE: We evaluated the prognostic value of serum creatinine level at initial treatment for future renal function in children with posterior urethral valves. MATERIALS AND METHODS: We reviewed the records of 35 patients with posterior urethral valves presenting in the first year of life and treated initially at our institution between 1973 and 1990 with valve ablation or vesicostomy. Initial assessment included serum creatinine determination, urine culture, renal ultrasonography and voiding cystourethrography. After 4 or 5 days of catheter bladder drainage renal ultrasound and serum creatinine measurement were repeated. At the end of followup patients were divided into 2 groups according to glomerular filtration rate calculated by the Schwartz formula: group 1--69 ml. or less per minute per 1.73 m.2 (median 15) and group 2--greater than 70 ml. per minute per 1.73 m.2 (median 110). Median followup was 102 months (8.5 years, range 50 to 219 months). RESULTS: Mean serum creatinine at diagnosis plus or minus standard deviation was 3.60 +/- 2.01 and 1.3 +/- 0.7 mg./dl. in groups 1 and 2, respectively (normal 0.1 to 0.6, p < 0.01). Mean serum creatinine after catheterization was 2.4 +/- 1.1 and 0.6 +/- 0.2 mg./dl. in groups 1 and 2, respectively (p < 0.01). Mean nadir creatinine during the first year of life was 1.7 +/- 0.6 and 0.4 +/- 0.2 mg./dl. in groups 1 and 2, respectively (p < 0.01). All differences were statistically significant. Linear regression analysis of creatinine after catheterization and glomerular filtration rate at last followup demonstrated a correlation coefficient of -0.7 (p < 0.01). CONCLUSIONS: Although it is well known that nadir creatinine in the first year of life correlates with prognosis, the correlation of long-term renal function with creatinine at valve ablation or vesicostomy is more useful to the clinician. These data indicate that serum creatinine level 4 to 5 days after the initial diagnosis correlates strongly with long-term renal function in children with posterior urethral valves.