Urethral instability and sacral nerve stimulation-a better parameter to predict efficacy?

Urodynamic parameters that predict the outcome of sacral nerve stimulation are difficult to define. We studied the predictive value of urethral instability and other urodynamic parameters on the efficacy of sacral nerve stimulation.

Patients with refractory voiding disorders were implanted with a neurostimulator after responding with more than 50% improvement in main symptoms after percutaneous nerve evaluation. Filling cystometry was performed with 3 urethral sensors and 1 bladder sensor at baseline and 6 months after implantation. Urethral pressure variations more than 15 cm H(2)O were considered pathological and defined as urethral instability. Clinical efficacy was evaluated by voiding diary data and defined as successful when greater than 50% improvement was observed.

A total of 19 female patients enrolled in the study. At baseline detrusor overactivity was observed in 9 patients, while 18 showed urethral instability. Sacral nerve stimulation therapy was successful in 13 patients (68%). The number of pads used per day and the severity of leakage decreased significantly. Of the 13 successfully treated patients 12 showed urethral instability at baseline. Detrusor overactivity was present in 4 successfully treated patients. Urethral instability disappeared in 7 of the 13 successfully treated patients and detrusor overactivity disappeared in only 1 of these patients.

In this study urethral instability appeared to be a valuable urodynamic parameter for predicting the outcome of sacral nerve stimulation.