AN ASSESSMENT OF THE CONTRIBUTION OF VISCOELASTIC FACTORS IN THE ETIOLOGY OF POOR COMPLIANCE IN THE HUMAN NEUROPATHIC BLADDER

Objective To compare the mechanical properties of full-thickness bladd er strips from poorly compliant neuropathic bladders with controls and to determine the overall contribution that mechanical factors might h ave in the aetiology of the poor compliance of medium-fill cystometry. Patients and methods The visco-elastic properties of full-thickness b ladder strips from 11 neuropathic patients (with poorly compliant blad ders during medium-fill cystometry) were compared with strips from 11 control bladders. A strip (measuring 2 cm long and 0.5 cm wide) was mo unted in an organ bath and stretched by 1 cm at a slow and at a fast r ate. The stretches were repeated in modified Krebs solution containing zero calcium and 12 mM magnesium. The final experiment involved stret ching the strip by 1 cm in <1 s (instantaneous stretch). Results 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 neuropath s 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, inte rmediate and slow components of viscous decay (derived from the rate o f tension decay following the instantaneous stretch) were not signific antly different in neuropaths compared to controls (P = NS). Conclusio n 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 betw een neuropathic and normal patients during medium-fill cystometry. Thi s implied that neurogenic rather than mechanical factors were more imp ortant in the aetiology of the observed poor compliance in these patie nts.