Combined evaluation of detrusor pressure and bladder wall thickness as a parameter for the assessment of detrusor function: an experimental in vivo study

PURPOSE: We developed a new method for assessing detrusor function, including active detrusor pressure in relation to bladder wall thickness. This parameter should enable the determination of bladder wall tension, defined as detrusor force per cross-sectional area of bladder tissue. MATERIAL AND METHODS: In acute studies in 8 male foxhounds sacral anterior roots S2 to S3 were placed into a modified Brindley electrode. The bladder was stimulated at different intravesical volumes with bladder filling in 50 ml. stages up to 700 ml. and intravesical pressure was measured and registered. The volume of bladder tissue was determined following cystectomy. Bladder tissue volume and bladder wall thickness were correlated with intravesical pressure during stimulation, resulting in the determination of detrusor force per cross-sectional area in N./cm.2 bladder tissue. RESULTS: The curve of the intravesical pressure rise during stimulation between 0 and 700 ml. showed a rapid incline with a maximum mean of 70.8 cm. water at 100 ml., followed by a slow decline. The bladder wall tension curve had an approximately symmetrical course with a slow incline, a maximum mean of 10.15 N./cm.2 at 350 ml. and a subsequent slow decline. CONCLUSIONS: The different curves of intravesical pressure and bladder wall tension show that these parameters are not identical. Combining detrusor pressure with bladder wall thickness enables further information on detrusor function to be obtained. Therefore, the clinical assessment of bladder wall tension may become a promising supplement to standard diagnostic methods with predictive value in patients with disturbed micturition.