An animal model of non-obstructive bladder instability.

Eight minipigs with proven normal bladder function have undergone a circumferential supratrigonal bladder transection. Urodynamic studies were performed before, and at various times up to eight months after operation. Over the same period biopsies were taken for physiological and histological studies. By three weeks after transection all animals had developed bladder instability, the abnormal contractions being maintained for the duration of the study. Concomitant with this change was the development, in vitro, of a non-specific detrusor smooth muscle supersensitivity similar to that which occurs in obstructed animals. By contrast with the latter group there was, however, no loss of cholinergic nerve from the transected bladder muscle. The transected (decentralised) minipig may be a useful model for the study of bladder instability not associated with outflow obstruction. The findings suggest that anatomical denervation is not a prerequisite for unstable contractions although a functional loss of nerve may be of importance. Supersensitivity, however, appears to occur in both obstructed and nonobstructed instability.