Mid-Term Kidney Function in Boys With Posterior Urethral Valves and a Solitary Functioning Kidney

It has been suggested that patients with posterior urethral valves (PUV) and a solitary functioning kidney (SFK) have poorer mid-term and long-term renal function than those with 2 functioning kidneys. We compared the mid-term estimated glomerular filtration rate (eGFR) of PUV patients with and without solitary kidneys.

We used the CIRCUP randomized controlled trial database, which included only patients with prenatally suspected, postnatally confirmed PUV. Standardized follow-up included an early dimercaptosuccinic acid (DMSA) scan performed between 1 and 6 months of age. We retrospectively compared mid-term eGFR (>5 years of age) between those with or without findings of solitary functioning renal unit (<10% differential function of a renal unit). eGFR was calculated using the updated Schwartz formula. Comparison between groups was performed using the Mann-Whitney U test. The study respects our national ethics regulations.

Sixty-eight PUV patients were included, 20 of whom had SFK. There were no differences in baseline characteristics between both groups, nor in timing of DMSA scan or latest follow-up. The median follow-up was 7 years (IQR: 6-8). The median eGFR in each group was SFK 82.5 (IQR: 55-109) vs 2 functioning kidneys 94.5 (IQR: 71-114). There was no significant difference in mid-term eGFR, nor in the proportion of boys with mid-term eGFR < 90 or eGFR < 60 between the 2 groups. However, nadir creatinine was significantly higher in boys with a mid-term eGFR < 90 as opposed to those with a mid-term eGFR > 90 (P < .01).

In boys with PUV, having only 1 functioning kidney on a DMSA study is insufficient to determine decreased renal reserve.