Correlation of in vivo bladder blood flow measurements with tissue hypoxia

Obstructive bladder dysfunction is in part due to reduced blood flow and the resulting ischemia of the bladder smooth muscle and mucosa. Our aim was to determine if the severity and localization of ischemia could be determined by measuring blood flow to the bladder with a non-invasive probe placed on the surface of the urothelium.

Twenty-four adult male rabbits (5 months, 3.5-4.0 kg) were divided into three groups: 1-controls; 2-2 h of bilateral ischemia; and 3-partial outlet obstruction, and were evaluated after 2 weeks. Each rabbit received an intraperitoneal injection of Hypoxyprobe-1. In vivo real-time monitoring of blood flow was measured at five sites within the bladders with a laser Doppler flowmeter.

For all groups, the blood flow readings showed no significant differences among the five sites. The ischemic bladders showed significant decreases in blood flow. The obstructed bladders had significantly lower blood flow than the ischemic bladders. The hypoxyprobe studies demonstrated that there was no hypoxia present in the control bladders; the mucosa of the ischemic bladders showed even hypoxia at an intermediate concentration; the obstructed bladders showed dense but even staining.

We have demonstrated that we can determine the severity of ischemia by surface measurement of blood flow.