Effect of chronic bladder outlet obstruction on blood flow of the rabbit bladder

Purpose: Previous studies have shown that the initial reaction of the rabbi t bladder to partial bladder outlet obstruction is increased blood flow at day 1 and a return to baseline blood flow at 1 week. Mucosal and muscle blo od flow followed this pattern but mucosal blood flow was always 4 to 5-fold greater. In this study we examined the effect of 4 weeks of outlet obstruc tion on bladder blood flow and correlated it with the severity of bladder c ontractile dysfunction. Materials and Methods: A total of 14 male New Zealand White rabbits underwe nt partial outlet obstruction creation by standard methods. After 4 weeks t he rabbits were anesthetized, and blood flow to the muscle and mucosa was d etermined by standard fluorescent microsphere technique. A section of each detrusor was used for in vitro contractility studies. Contractile responses to field stimulation, carbachol and potassium chloride were determined. A section of each detrusor tissue was fixed in formalin and used to determine the smooth muscle volume fraction. Results: Four weeks of partial bladder outlet obstruction caused a signific ant and variable increase in bladder weight and a decrease in blood flow to bladder muscle without changes in the blood flow to mucosa. There was a cl ear correlation between the severity of contractile dysfunction, bladder we ight and the magnitude of the decrease in blood flow in muscle. The smooth muscle volume fraction remained stable at approximately 40%. Conclusions: Bladder decompensation was associated with decreased blood flo w to bladder smooth muscle. Because compensated obstructed bladders with re latively normal contractile function are also hypertrophied but have normal blood flow, decreased blood flow in decompensated bladders is not simply a response to bladder hypertrophy. From this study we hypothesize that decre ased blood flow to bladder smooth muscle is an etiological factor in bladde r contractile dysfunction (bladder decompensation) secondary to partial out let obstruction.