The effect of intravesical resiniferatoxin in patients with idiopathic detrusor instability suggests that involuntary detrusor contractions are triggered by C-fiber input.

PURPOSE

We evaluated the role of bladder C-fiber input in involuntary detrusor activity in patients with idiopathic detrusor instability.

MATERIALS AND METHODS

Filling cystometry and a voiding chart were done in 13 patients with idiopathic detrusor instability. The first detrusor contraction, maximal cystometric capacity, daily frequency and the number of episodes of urinary incontinence were determined. A 50 nM. solution of resiniferatoxin, a specific C-fiber neurotoxin, was then instilled in the bladder for 30 minutes. Patients were reevaluated 30 and 90 days later.

RESULTS

Resiniferatoxin instillation delayed or suppressed involuntary detrusor contractions during filling cystometry. The mean first detrusor contraction plus or minus standard deviation increased from 170 +/- 109 ml. at baseline to 440 +/- 130 ml. (p = 0.0001) at 30 days and to 391 +/- 165 ml. (p = 0.008) at 90 days. Mean maximal cystometric capacity increased from 291 +/- 160 to 472 +/- 139 ml. (p = 0.01) at 30 days and to 413 +/- 153 ml. (p = 0.1) at 90 days. The mean number of episodes of urinary incontinence daily decreased from 4.3 +/- 2.7 to 0.9 +/- 2.7 (p = 0.001) at 30 days and to 0.7 +/- 0.9 (p = 0.009) at 90 days. Mean frequency daily also decreased from 12 +/- 3.2 to 9.7 +/- 3.2 (p = 0.003) and to 9.9 +/- 3.5 (p = 0.001) times at the same time points, respectively.

CONCLUSIONS

C-fiber input seems to have an important role in the generation of involuntary detrusor contractions and lower urinary tract symptoms in patients with idiopathic detrusor instability. Substances that block C-fiber input may represent a new strategy for treating this bladder dysfunction.