Comparative urodynamic patterns of bladder pressure, contractility and urine flow in man and rat during micturition

A urodynamic characterization of the distinctive patterns of normal micturition in man and rat was undertaken. Data were obtained from experimental studies where bladder pressure was measured suprapubically obviating urethral instrumentation. Ambulatory urodynamic studies were conducted with 17 asymptomatic male volunteers. Bladder pressure was monitored via a supra-pubic catheter and abdominal pressure via a rectal balloon using a UPS2020 ambulatory system. Average duration of each monitoring period was 20.5 hours. Detrusor pressure and flow rate records from each subject were identified and consecutive filling and voiding phases were averaged over the entire monitoring period using the onset of micturition as a time marker. The averaged pattern of pressure, flowrate, cumulative volume, and contractility curves for each subject as well each for group was computed and graphically presented. For comparison, the micturition phase of 18 anesthetized rats were used. A continuous CMG was performed and bladder pressure was recorded suprapubically. For each group the averaged parameters of urethral opening pressure, Max Detrusor pressure, Detrusor pressure at Max flowrate, bladder capacity, and WF were extracted and compared statistically. Numerical values are M +/- SE. The urodynamic temporal patterns observed during the micturition phase of the CMG in terms of detrusor pressure and associated flow, in both man and rat posses striking qualitative similarities. These are particularly striking during the onset of micturition in the great majority of animals. Furthermore the pressures generated by the bladder before and during micturition are quantitatively similar. However there were also distinct differences particularly in the pattern observed during voiding when bladder pressure was oscillatory. The temporal sequence of detrusor pressure and flow in man and rat contains many qualitative and quantitative similarities rendering the rat's potential as a particularly useful model in the study of the onset of micturition.