BACKGROUND: Up to 15% of children with posterior urethral valves (PUV) will progress to end-stage kidney disease and undergo kidney transplant (KT) during childhood. Progressive kidney function deterioration may be secondary to congenital dysplastic changes, exacerbated by ongoing poor bladder dynamics. Post-KT bladder dynamics in PUV patients are poorly understood, and these patients remain at risk for adverse outcomes. To better understand the potential impact of bladder dysfunction, we compare long-term allograft function (eGFR) of PUV patients against a cohort of children with isolated dysplasia and normal bladder function. We hypothesized that PUV patients would have worse eGFR than isolated dysplasia patients, secondary to the ongoing impact of the “valves bladder.”
METHODS: We reviewed our institutional transplant database (Jan2000- Dec 2023) and identified PUV patients matched 1:1 with males with isolated dysplasia patients, according to age at the time of KT. We excluded other forms of underlying etiology for renal failure. We collected data on age, weight, and BMI at the time KT and time to nadir creatinine, most recent eGFR and eGFR at a censored follow-up time to ensure similar monitoring time between groups. Bedside Schwarts was used for eGFR calculation. We also collected PUV-specific variables, including age and type of initial surgical intervention, pre- and post-KT anticholinergic and alpha-blocker use, videourodynamics (VUDS), and clean intermittent catheterization (CIC) and posterior urethral valve risk of chronic kidney disease (PURK) score.
RESULTS: We included 31 PUV patients (patient demographics Table 1) and 31 matched controls with isolated dysplasia. For PUV patients, primary valve ablation occurred in 58%, creatinine at one year was 150 umols/L(IQR 239), and 66% had a PURK score of > 4. Pre-KT anticholinergics were used in 48%, alpha-blockers in 32% and CIC in 48%. Post KT, anticholinergics, CIC and alpha blockers were utilized in 52% of patients, representing a significant increase in alpha-blocker use(p<0.01). VUDS was carried out in 19% of PUV patients, demonstrating bladder capacity appropriate for age in 66% and smaller in 33%. Compared to dysplasia controls, patient characteristics were similar in both groups(Table 2.), including age at KT, follow-up time, and weight. PUV patients had a significantly longer time to nadir creatinine after KT(19 days +/- 20) than dysplasia patients(10 days+/-9) (p=0.02), and significantly lower eGFR at follow-up PUV(68.9 +/- 30) vs. dysplasia (85.2 +/- 19)(p=0.02).
CONCLUSIONS:
At a similar follow-up time, we noted that children with PUV had significantly lower eGFR than children who underwent KT for isolated renal dysplasia. These data suggest that poor bladder dynamics found in PUV patients may lead to negative consequences for the transplanted kidney. This provides evidence for the importance of close ongoing attention and proactive management of bladder function in PUV patients before and after KT.
