Urethral ratio on voiding cystourethrogram: a comparative method to assess success of posterior urethral valve ablation.

OBJECTIVE: To develop a simple, objective and reproducible quantitative measurement to assess success of posterior urethral valve ablation.

METHOD: In 30 patients with posterior urethral valves the diagnosis was confirmed by voiding cystourethrogram (VCUG). Our protocol was to perform valve ablation, and repeat VCUG at 12 weeks postoperatively. Urethral ratio was calculated by dividing the posterior urethral diameter by the anterior urethral diameter. Thirty males undergoing VCUG for urinary tract infections were evaluated as normative controls.

RESULTS: Median age of controls was 12 months (2 days-6 years) and of study group was 13 months (1 day-11 years). Mean urethral ratio in pre-fulguration group was 4.94 (+/-2.97) and in post-fulguration group was 2.134 (+/-1.19) (P<0.001). The mean urethral ratio in the control group of 1.73 (+/-0.577) was significantly different from the pre-fulguration group result (P<0.001), but not significantly different in comparison to the post-fulguration group (P=0.104).

CONCLUSION: Calculation of urethral ratio on VCUG as a method of assessment of outcome of fulguration is objective, reproducible, and allows preoperative and postoperative VCUG from different facilities to be compared. A post-fulguration urethral ratio of 2.5-3 represents an acceptable result postoperatively.