Vascular response of the rabbit bladder to chronic partial outlet obstruction

Partial outlet obstruction of the rabbit urinary bladder results, initially , in a rapid increase in bladder mass and remodeling of the bladder wall. P reviously, it was shown that this response was characterized by serosal gro wth (thickening) which was apparent after 1 day of obstruction, before any visible vascularization was observed. After 1 week of obstruction, signific ant microvessel formation was seen in the transition region between the det rusor smooth muscle and the thickening serosa; after 2 weeks the entire ser osa was vascularized. In this study we investigated the effect of chronic (4 week) partial outlet obstruction on microvessel density and distribution in the bladder wall im munohistochemically using CD31 as a marker for vascular endothelium. Transv erse sections of bladder wall were examined after 4 weeks of no surgery, sh am surgery or partial obstruction. The microvessel density of the obstructed rabbit bladder mucosa and detruso r smooth muscle increased relative to augmentation of these compartments wh ile new vessels appeared in the thickening serosa. Although vessel density did not change with obstruction a significant shift in mean vessel circumfe rence to the left occurred indicating a significant increase in the number of microvessels and small vessels consistent with angiogenesis.