Urinary bladder blood flow changes during the micturition cycle in a conscious pig model

To develop a method using laser Doppler flowmetry in conscious pigs, which allows the accurate simultaneous measurement of cystometric and cardiovascular parameters together with changes in vesical blood flow. The animal model was then used to investigate the changes in blood flow in the urinary bladder which occur during the micturition cycle.

Seven large white female pigs were subjected to chronically implanted vascular access and urodynamic catheters as well as an intramural vesical laser Doppler probe. The animals underwent repeated conscious urodynamics with simultaneous measurement of cardiovascular, urodynamic and vesical blood flow parameters.

The model shows both compliant and low-compliance behavior and allows greater investigation of the effects of intravesical pressure on blood flow. Blood flow is not altered, during compliant filling and voiding transiently decreases flow to 38% of resting levels, with a rapid return to normal. Low-compliance filling results in a progressive fall in blood flow to a minimum of 45% of normal. At all times an inverse relationship between intravesical pressure and blood flow is maintained.

The pig model proved to be well suited to the experimental conditions and provided reproducible results. The principal determinant of blood flow within the wall of the bladder is the pressure within its lumen. During normal filling the blood supply of the bladder is able to adapt to the large increase in surface area which occurs, maintaining blood flow until the pressure increases.