Urethral ratio in predicting residual valve following ablation of posterior urethral valve.

OBJECTIVE

The aim of this study is to evaluate the use of urethral ratio as a tool for predicting residual valve following ablation.

MATERIALS AND METHODS

This is a prospective observational study conducted in our center for a period of one year. Forty-nine patients were diagnosed with case of Posterior Urethral Valve (PUV) by Micturating Cystourethrogram (MCUG) and confirmed with cystoscopy along with ablation of the valve in same setting. At three months follow up, MCUG and cystoscopy were done to check for residual valve. Posterior:anterior urethral ratio (PUR) was calculated from MCUG at the time of diagnosis and at three months follow up. PUR before ablation and at three months follow up were compared. PUR at three months follow up was compared to the clinical features and cystoscopic findings for confirmation of residual valve.

RESULTS

A total of 49 patients admitted with the diagnosis of PUV were included in the study. Out of 49 patients, four (eight%) had residual valve after ablation diagnosed on cystoscopy at three months. On MCUG, all had dilated posterior urethra with irregular outline of bladder prior to ablation. The mean of Posterior:anterior urethral ratio (PUR) prior to ablation was 2.71 ± 0.46, and after ablation at three months was 1.90 ± 0.30, which was statically significant (p < 0.001). On subgroup analysis of the group without residual valve (n = 45), the mean PUR was 2.66 ± 0.43 and 1.85 ± 0.25 before and after ablatio respectively, while in those with residual valve (n = 4) the mean was 3.32 ± 0.31 and 2.48 ± 0.19 before and after ablation (p = 0.362). An ROC curve was plotted to find the cut off for presence of residual valve. The cut off value was 2.41 with a sensitivity of 95 %, specificity of 100 %, positive predictive valve of 33.33 % and negative predictive value of 100 %.

CONCLUSION

Posterior:anterior (PUR) calculated from MCUG is predictor of presence of PUV. It can also be a valuable tool for evaluation of success or failure following ablation. PUR above 2.41 should be evaluated with cystoscopy.