Diagnostic performance of posterior: Anterior urethra ratio on postoperative micturating cystourethrogram for residual posterior urethral valves: A systematic review and meta-analysis.

BACKGROUND: Posterior urethral valves (PUV) remain an important contributor to childhood chronic kidney disease. After endoscopic valve ablation, residual valves may perpetuate obstruction and worsen renal and bladder outcomes. The posterior: anterior urethral ratio (PAR) on postoperative micturating cystourethrogram (MCUG) is a simple quantitative measure that may help detect residual valves, but reported thresholds and accuracies vary widely. We aimed to evaluate the diagnostic performance of PAR on postoperative MCUG for detecting residual PUV, using cystoscopy as the reference standard.

METHODS: This review was conducted in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guideline extension for diagnostic test accuracy reviews and a protocol was a priori registered in PROSPERO (CRD420251010994). PubMed, Scopus, EMBASE and Web of Science were searched on 23 June 2025 for English-language studies in which PAR on postoperative MCUG was used to diagnose residual valves after ablation, with check cystoscopy as reference standard. The risk of bias among the included studies was assessed using QUADAS-2 tool. Two reviewers independently performed data extraction and constructed 2 × 2 tables for each study. Pooled sensitivity and specificity were estimated, and a summary receiver operating characteristic (sROC) curve was constructed using a bivariate random-effects model (Stata 'midas').

RESULTS: Seven studies (n = 565; 398 PUV, 167 controls) met the inclusion criteria for the systematic review; six were included in the meta-analysis. Reported PAR cut-offs for residual valves ranged from 1.2 to 3.5. Pooled sensitivity was 0.77 (95% credible interval [CrI] 0.54-0.90), pooled specificity was 0.95 (95% CrI 0.78-0.99), and the sROC area under the curve was 0.91 (95% CrI 0.88-0.93), with high specificity but only moderate sensitivity. Among the included studies, the majority had low risk of bias for the index test (six out of seven studies) and reference standard (all seven studies), but two studies had high risk in the patient selection and three studies had high risk in flow/timing domains. Also, the risk of applicability was low for all studies in most of the domains.

CONCLUSION: Postoperative PAR on MCUG demonstrates a specificity of 95% and a sensitivity of 77% for detecting residual PUV. Given the wide variation in PAR thresholds and heterogeneity among the included studies, the pooled estimates are promising, yet hypothesis-generating. Interpretation of these results should be cautious and cannot be construed as prescriptive. Further high-quality multicentric studies are needed to validate these results.