The effect of intravesical capsaicin on the suburothelial innervation in patients with detrusor hyper-reflexia

Objective To determine the effect of intravesical capsaicin on the suburoth elial innervation in patients with detrusor hyper-reflexia, in whom a singl e dose of intravesical capsaicin (1-2 mmol/L) increases the bladder capacit y for 3-6 months. Patients and methods Thirteen patients with detrusor hyper-reflexia underwe nt cystometry and had flexible cystoscopic biopsies taken before and 6 week s after receiving instillations of intravesical capsaicin (1 mmol/L). Simil ar biopsies were also obtained from a control group of 12 neurologically no rmal patients with microscopic haematuria and normal bladders. Frozen secti ons were stained using antibodies to S100 and PGP 9.5. Using computerized a nalysis, the mean nerve density scores were expressed as nerves/mm(2) for S 100-positive structures and 'red%' and 'red in frame' for PGP 9.5. Results,The mean (sem) functional bladder capacity increased from 193.2 (28 .17) mL, before to 396.3 (41.96) mt at 6 weeks after treatment with capsaic in, in nine of the 13 patients. The mean nerve density of S100-positive str uctures in the control group was 83 (3.18) nerves/mm(2). In hyper-reflexic patients who responded to capsaicin by improved bladder capacity, the mean nerve density of S100-positive structures was reduced from 100 (12.2) befor e to 66 (9.4) nerves/mm2 6 weeks after treatment. In those who did not resp ond to capsaicin there was no significant difference in these scores, Simil arly the 'red%' and 'red in frame' reduced from 3.41 (1.06) to 1.15 (0.32) and 824.7 (246.3) to 297.9 (83.5) units, respectively, before and 6 weeks a fter capsaicin treatment. The difference in those not responding was not si gnificant. Conclusions Intravesical capsaicin causes a reduction in suburothelial nerv e densities in the bladder of patients with detrusor hyper-reflexia. This m ay explain its prolonged beneficial effect in these patients.