Blood flow, pressure and compliance in the male human bladder

Purpose: The regulation of human bladder blood flow during filling is poorly understood. We characterized changes in bladder blood flow with filling and examined the relationship of bladder compliance and blood flow. Materials and Methods: A total of 17 awake male patients underwent saline cystometry followed by cystoscopy while under local anesthesia, during which a laser Doppler flow probe was placed into the posterior bladder wall detrusor. Systemic blood pressure, bladder blood flow and intravesical pressure were measured with the bladder empty and filled to 25%, 50%, 75% and 100% of awake maximum cystometric capacity as well as immediately after bladder drainage. Results: Mean bladder blood flow was lowest in the empty bladder and increased with bladder filling. A mean peak flow plus or minus standard error of 7.6 +/- 1.1 ml. per minute per 100 gm. tissue was observed at volumes greater than 75% but less than 100% of maximum cystometric capacity. At 100% maximum cystometric capacity mean intravesical pressure increased by 73% from 25.2 to 43.5 cm. water and bladder blood flow decreased by 36%. Rapid bladder drainage was associated with a rebound in mean bladder blood flow to approximately 1.6 times baseline. Bladder compliance calculated for the whole filling curve positively correlated with bladder blood flow (p = 0.025), that is low compliance was associated with low blood flow. Conclusions: Human bladder blood flow tends to increase with increasing volume and pressure, and depends largely on local regulation. At capacity bladder blood flow is significantly decreased. Immediately after bladder drainage there is a rebound in blood flow, allowing reperfusion to occur. Decreased bladder blood flow and decreased bladder wall compliance correlated strongly, suggesting that ischemia may lead to structural changes in the bladder wall.