An assessment of the contribution of visco‐elastic factors in the aetiology of poor compliance in the human neurophathic bladder

Abstract

To compare the mechanical properties of fullthickness bladder strips from poorly compliant neuropathic bladders with controls and to determine the overall contribution that mechanical factors might have in the aetiology of the poor compliance of medium-fill cystometry. The visco-elastic properties of full-thickness bladder strips from 11 neuropathic patients (with poorly compliant bladders during medium-fill cystometry) were compared with strips from 11 control bladders. A strip (measuring 2 cm long and 0.5 cm wide) was mounted in an organ bath and stretched by 1 cm at a slow and at a fast rate. The stretches were repeated in modified Krebs solution containing zero calcium and 12 mM magnesium. The final experiment involved stretching the strip by 1 cm in < 1 s (instantaneous stretch). Only modest differences in the peak tensions of both tissues were uncovered by the slow and fast stretches (fast stretch: 14.6 +/- 5.5 in neuropaths vs 10.1 +/- 4.1 g in controls, P = NS; slow stretch: 9.6 +/- 3.5 in neuropaths vs 6.7 +/- 2.5 g in controls, P < 0.05). Stretches carried out in modified Krebs solution resulted in lower tensions. Fast, intermediate and slow components of viscous decay (derived from the rate of tension decay following the instantaneous stretch) were not significantly different in neuropaths compared to controls (P = NS). The differences in the mechanical properties between neuropathic and control bladder strips were small and could not alone have accounted for the large differences in bladder compliance that was observed between neuropathic and normal patients during medium-fill cystometry. This implied that neurogenic rather than mechanical factors were more important in the aetiology of the observed poor compliance in these patients.