Correlation between histological changes and urodynamic parameters in detrusor instability

Introduction: There are distinct histological changes observed in both neuropaths (N) and patients with idiopathic (I) detrusor instability (DI) where there is a patchy distribution of areas that consist of muscle bundles with hypertrophied muscle cells, increased collagen and elastin infiltration, and decreased nerve counts that are juxtaposed to normal areas. This study correlates the amount and severity of these changes with the urodynamic findings. Patients and methods: Detrusor biopsies from 17 patients with DI (10 IDI and seven N) and four controls (C) removed at open surgery were fixed and stained to detect collagen, muscle and elastin. A Leica Q500 image analyser was used to acquire data concerning fibre diameter and the proportions of collagen, muscle and elastin. Pre-operative urodynamics were used to determine compliance (mL/cniH,0) and mechanical power at maximum flow (Qmaxx Pdex) and these were correlated with the amount and severity of the histological changes. (Nine of 10 patients with I, foru of seven with N and all four controls had filling rates of 50100 mL/min, the rest were filled at 20 mL/min). Results: In nine patients (five IDI. four N) there was no correlation between the total areas of muscle, collagen or elastin. In 13 patients there was no correlation between detrusor power at Qmaxand changes observed in damaged areas. There was a trend between compliance and the elastin and collagen content in the damaged areas, but the only significant correlations were between the compliance and the percentage of muscle in the damaged areas, and the mean fibre diameter in these areas. Conclusions: Changes in areas of damaged tissue and the total amount of damaged tissue is highly variable in DI. Generally, the microscopic changes correlate poorly with urodynamic findings. In the whole bladder it is thought the reduction in compliance in DI reflects increases in collagen deposition. Here, only muscle volume and fibre diameter in the damaged areas correlated significantly with the urodynamics. If the biopsies are representative, one interpretation is that altered compliance may have a myogenic component. © 1998 British Journal of Urology.