Pop-off mechanisms as renoprotective mediators in children with posterior urethral valves: A systematic review and meta-analysis

Abstract Background Pop-off mechanisms are potential pressure-relieving mediators in patients diagnosed with posterior urethral valves (PUV). These mechanisms include, among others, urachal persistence, urinomas, bladder diverticula and unilateral high-grade vesicoureteral reflux. The aim of this systematic review was to synthesize the existing evidence regarding the protective effect of pop-off mechanisms on renal function in children with PUV. Methods We conducted a systematic review of the literature that involved an extensive search in the main databases of medical bibliography. Three independent reviewers selected the relevant articles based on the previously defined inclusion and exclusion criteria. Methodological quality of the selected article was rated using the Newcastle Ottawa Scale index. Data extraction was performed by three independent reviewers. We used random meta-analyses to compare different outcomes (serum creatine, Nadir serum creatinine, and renal failure) between children with PUV and pop-off mechanisms and those with PUV but without pop-off mechanisms. Results 10 studies with data from 896 participants were included in this review. The age of the participants ranged from 0 to 25 years. Seven articles reported serum creatinine values for each group and 3 of them found significant differences between groups. The random-effects meta-analysis for serum creatinine showed significant lower mean (diff=-52.88 µmol/L [95% CI -73.65 to -32.11]) in the group of children with pop-off mechanisms, and the random-effects meta-analysis for Nadir serum creatinine showed a marginally significant lower mean in the group of children with pop-off mechanisms (diff=-12.00 µmol/L [95% CI -24.04 to 0.04]). The random-effect meta-analysis for renal failure resulted in a significant risk reduction on the group of children with pop-off mechanisms (odds ratio = 0.48 [95% CI 0.23 to 0.98]). Conclusions Children with PUV and pop-off mechanisms show better renal function and lower risk of renal failure than those with PUV but without pop-off mechanisms suggesting these mechanisms may act as renoprotective mediums. The high heterogeneity between studies in the assessment of renal function and long-term outcomes compel to interpret these findings with caution. Future studies that stratify by the different types of pop-off mechanisms and use standardized metrics, such as Nadir creatinine are needed.