Effects of vesical and perfusion pressure on perfusate flow, and flow on vesical pressure, in the isolated perfused working pig bladder reveal a potential mechanism for the regulation of detrusor compliance.

AIMS: Although there is evidence that deficits in bladder blood flow negatively impact bladder function, the effects of vesical, and perfusion pressures on bladder perfusion (perfusate flow), and of perfusate flow on vesical pressure, remain poorly understood. The present study used the isolated perfused working pig bladder model to examine the relationships between blood flow, and vesical and perfusion pressures.
METHODS: Vesical arteries of pig bladders obtained from a local slaughterhouse were cannulated and perfused with Krebs-Henseleit solution at different pressures, and with carbachol to cause bladder contraction. The urethra of each bladder was cannulated to permit filling (10 mL/min), isovolumetric contraction and emptying. A ureter was cannulated with a pressure sensor to monitor vesical pressure.
RESULTS: When at rest (50 mL vesical volume), bladder vesical pressure was 8.06 ± 1.5 mmHg and perfusate flow driven by a pressure gradient of 105 mmHg was 22.5 ± 2 mL/min (58.9 ± 7.8 mL/min-100 g). During filling, vesical pressure increased and flow decreased, but not necessarily in-parallel. Perfusate flow decreased transiently during isovolumetric contraction, and flow increased during emptying. A reduction in perfusion pressure from ∼105 to ∼40 mmHg reduced flow from ∼70 to ∼20 mL/min-100g, and reduced flow correlated with reduced vesical pressure.
CONCLUSION: Perfusate flow is dependent on bladder perfusion pressure, and not necessarily reciprocally dependent on vesical pressure. Vesical pressure is highly sensitive to the level of perfusate flow, which supports the hypothesis that vesical pressure is dependent on the level of detrusor smooth muscle contractile activity (tone), and that compliance is dependent on bladder perfusion.