Setting the speed limit: a pilot study of the rate of serum creatinine decrease after endoscopic valve ablation in...

In neonates with a posterior urethral valve serum creatinine is increased. It decreases after successful relief of obstruction. Clinicians consider urinary diversion if serum creatinine remains increased. However, the optimal rate of decrease of serum creatinine is not defined. We generated useful data on the rate of serum creatinine decrease in neonates with a posterior urethral valve by introducing the idea of a prediction curve.

We reviewed the medical charts of 15 consecutive children treated for a posterior urethral valve in the neonatal period at our institute between 2002 and 2007. The 11 children with a delayed diagnosis of a posterior urethral valve were excluded from analysis. Serial serum creatinine levels in the cohort of 15 patients were analyzed to estimate 1) the rate of decrease after valve ablation and 2) the time needed to achieve a nadir.

One child died of renal insufficiency on day 10 of life and was excluded from study. Serum creatinine attained a nadir at about age 6 months but 73% of the total decrease occurred within the first 2 months of life, which was also equal to a 45% decrease from the peak values recorded soon after birth. The rate of decrease did not appear to be influenced by the peak values. Children with normal peak creatinine or intercurrent problems did not follow the trend.

The rate of decrease in serum creatinine in the first few months of life may provide useful information on the adequacy of valve ablation.