DIFFERENCES IN DETRUSOR CONTRACTILE FUNCTION IN WOMEN WITH NEUROPATHIC AND IDIOPATHIC DETRUSOR INSTABILITY

Objective To compare urodynamic indices of isometric and isotonic detr usor contractile function between patients with idiopathic detrusor in stability and patients with multiple sclerosis (RIS) and detrusor hype r-renexia and thus determine whether the different types of detrusor i nstability share a common pathophysiological pathway. Patients and met hods Two groups of women were studied; 1139 neurologically normal pati ents with detrusor instability (mean age 55 years, so 17) and 141 with multiple sclerosis (MS) and detrusor hyper-reflexia (mean age 45 year s, so 11), Patients were assessed using static water cystometry, exami ning storage function, isometric and isotonic detrusor contractile fun ction and voiding outflow function, Results Bladder capacities were lo wer in the MS group, with a median of 357 mt, 95% confidence interval (CI) 305-400 mL, compared with the neurologically normal patients (med ian 450 mt, 95% CI 425-450, P<0.001, Mann-Whitney U-test). Voiding was incomplete in the MS group, with a median (95%CI) residual volume of 100 (100-125) mL, but complete in the normal group, at 10 (10-10) mL. Higher median (95% CI) detrusor pressures at urethral opening (P-det o pen) and closing (P-det close) were recorded in the MS group than in t he neurologically normal group, at 35.5 (33.2-46.6) cmH(2)O and 30 (27 .6-31.6) cmH(2)O for P-det open, respectively (P = 0.003), and 25.3 (2 0.9-31.6) cmH(2)O and 16.6 (15.0-18.1) for P-det close, respectively, (P=0.001). In the MS group, the median (95% CI) isometric unstable con tractions were less well maintained, but were more powerful, at 17.6 ( 15.6-18.9) N, compared to the neurologically intact group at 14.4 (14. 0-14.9) N (P=0.002), In the MS group, contractions frequently did not relax back to baseline, whereas in the group with detrusor instability , full relaxation after contraction was more usual. There was no signi ficant difference in the maximum speed of detrusor shortening (isotoni c activity), measured by the velocity constant Q, between the groups (median for both groups 20 mL/s, 95% CI 17-23). Conclusion These resul ts show differences in storage function, isometric detrusor contractil e function and voiding outflow function between detrusor instability a nd detrusor hyper-reflexia, indicating that the two conditions may not share a common pathophysiological pathway.