Overcoming diagnostic uncertainty in late-childhood posterior urethral valves: Validation of the bladder outlet obstruction index in male children

Objective Posterior urethral valves (PUV) are the most common cause of congenital bladder outlet obstruction (BOO) in male children. Late presentations of PUV pose a diagnostic challenge due to nonspecific symptoms and the absence of a standardized diagnostic algorithm. The aim of this study was to assess the use of the BOO index in children diagnosed with PUV in late childhood. Methods A retrospective review included male patients aged 5–15 years diagnosed with and treated for PUV between January 2002 and December 2023. Detrusor pressure at maximum flow rate (P det Q max ) was plotted against the maximum flow rate, and cluster analysis was used to identify the axis that best differentiated obstructed (pre-endoscopic valve ablation [EVA]) from unobstructed (post-EVA) cases. Results We identified 53 patients with PUV presenting in childhood. Cluster analysis of P det Q max and maximum flow rate (Q max ) values suggested an axis of P det Q max =2×Q max +40 as the best separator between obstructed and unobstructed cases, similar to adult males with prostatic BOO. Conclusion Diagnostic tests for congenital PUV presenting in childhood are lacking. Our data suggest that the BOO index threshold of >40 used to diagnose adult BOO is also valid to diagnose PUV in children when combined with voiding fluoroscopy, though further validation in larger and independent cohorts is warranted.