Ability of obstructed bladders to empty is dependent on method of stimulation

To correlate pharmacologic changes that occur in the bladder after a partial outlet obstruction with the bladder's ability to perform work and empty.

After 2 weeks of partial outlet obstruction, rabbit bladders were stimulated in vitro both isovolumetrically [field stimulation (FS)] and to empty (FS, bethanechol, and KCl).

The obstructed bladders were separated into two groups according to their ability to empty when stimulated with FS. Compensated bladders were those that could empty as much as controls. Decompensated bladders emptied significantly less than controls. With FS and bethanechol, the compensated obstructed bladders showed no difference from the control bladders in their ability to empty. In contrast, with KCl, the compensated bladders generated significantly less pressure, performed less work, and emptied less than controls. When the decompensated bladders were stimulated with all three types of stimulation, all parameters, including emptying ability, were significantly decreased.

The reduction in the response of compensated bladders to KCl stimulation suggested that the initial defects to the bladder after an outlet obstruction involved the interaction of smooth muscle proteins with calcium and ATP. In contrast, the response of decompensated bladders to all three forms of stimulation was equally reduced, suggesting that the degenerative processes were directly related to significant cellular damage to metabolic processes involved in energy synthesis, storage, and utilization.