Causes of failed urethral botulinum toxin A treatment for emptying failure

Urethral injection of botulinum toxin A (BTX-A) can reduce urethral resistance in patients with voiding dysfunction. However, some patients do not benefit from this treatment. It is essential to identify the causes for these failed procedures.

A total of 200 patients receiving urethral BTX-A injections for voiding dysfunction refractory to conventional medication during a 5-year period were included in this study. The patients received 50 or 100 U of BTX-A injected into the urethral sphincter. Treatment was considered successful when patients were subjectively satisfied with the outcome and (a) patients with chronic urinary retention resumed spontaneous voiding, (b) patients with a large postvoid residual volume had a reduction in postvoid residual of more than 50%, (c) patients voided with a lower detrusor pressure or lower abdominal pressure to urinate adequately. The therapeutic results and causes of failed treatment were retrospectively analyzed.

The overall success rate was 88.5% (177 patients), including 47.5% (95 patients) with an excellent result and 41% (82 patients) with an improved result. The causes of failed treatment in 23 patients were detrusor underactivity with very low abdominal straining pressure in 7, a tight urethral sphincter in 7, bladder neck obstruction in 7, and psychological inhibition of voiding in 2. Transurethral incision of the bladder neck was performed in 7 patients, and all had an improved result.

BTX-A urethral treatment failed in 11.5% of patients with voiding dysfunction refractory to medical treatment after one session. Careful investigation of the underlying causes of failed treatment is mandatory to achieve a satisfactory outcome.