Duration of increased mucosal permeability of the urinary bladder after acute overdistension: an experimental study in rats

The duration of damage to the mucosal barrier of the urinary bladder after overdistension was investigated in a rat model. Overdistension was induced for 3 h in 48 female Sprague-Dawley rats by forced diuresis and balloon obs truction of the bladder neck. In 24 rats 0.5 mi of 2% solution of Trypan bl ue in 0.9% NaCl solution was instilled into the bladder for 1 h at 0 h, 24 h, 48 h, 7 days and 21 days after overdistension. After dyeing, full-thickn ess samples were taken from the wall of the bladder dome and body immediate ly above the ureteral orifices for histological studies. Inflammatory react ion was investigated histologically without Trypan blue dyeing in 24 rats a t 0 h, 24 h, 48 h, 7 days and 21 days after overdistension. At 0, 24 and 48 h after overdistension the bladder wall was deep blue throughout. The dome and body were similar. At 7 days there was only slight staining of the bla dder surface urothelium and subjacent connective tissue, while at 21 days t here was no longer any dye in the bladder wall or urothelium. Oedema reache d its maximum at 48 h, and large numbers of inflammatory cells were seen in the submucosa at 48 h. These changes had normalized by 7 days. After overd istension urothelial integrity is destroyed for several days, making it pos sible for different substances in the urine to penetrate into the bladder w all. This renders questionable the use of bladder distension in the treatme nt of interstitial cystitis, as it may only increase leakage of the urothel ium and accelerate inflammatory reaction in the bladder wall. However, in t he present study of healthy rat bladders the integrity of the urothelium ha d recovered to a large extent after 1 week and completely after 3 weeks.