INFLUENCE OF TRANSIENT OVERDISTENSION ON BLADDER WALL MORPHOLOGY AND ENZYME-HISTOCHEMISTRY

Bladder overdistension has been found to cause transitional morphologi cal changes in innervation which correlate with changes in micturition and bladder contractility. We investigated the influence of overdiste nsion on bladder wall morphology using histological and enzyme histoch emical methods. Overdistension was induced in female rats for 3 h by f orced diuresis and balloon obstruction of the bladder neck. Oedema was seen beneath the mucosa at 12 h, with hyperemia and haemorrhages. The urothelium was mostly intact, although enzymes leaked out of the epit helial cells. The changes were increased at 24 h. The urothelium also showed some disruptions and degenerative vacuolization. The oedema rea ched its maximum at 48 h, and large numbers of inflammatory cells were also seen. The urothelium was disruptured in many places and vacuolat ed, but the subendothelial capillaries remained normal. Damage to some musele cells was seen. After 7 days the oedema had disappeared and th e urothelium was continuous. Enlarged nuclei were seen as white spots in the epithelial cells. Numbers of inflammatory cells were similar to those in the controls. Overdistension causes damage primarily to the bladder urothelium, and to a lesser extent to the muscular layer. Urot helium integrity is destroyed for several days, which makes it possibl e for various substances to penetrate the bladder wall and allows for bacterial adherence. The damage however is, almost completely healed w ithin one week.