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.