Cystometry in mice--influence of bladder filling rate and circadian variations in bladder compliance

Meaningful interpretation of cystometric measurements in experimental animals requires detailed analysis of factors that could affect the results. In the present study, the effect of catheter size and bladder filling rate were studied in detail; in addition, the influence of (day) time on bladder compliance was assessed by cystometry in mice. Bladder reservoir function was independent of the catheter size, when i.v. cannulae with outer diameters of 0.6 and 0.8 mm. were used, but leakage pressure and leakage volume were increased with the larger catheter. Neither the storage capacity nor the bladder wall resistance showed dependence on filling rates above 0.1 ml./min. Below this rate, bladder capacity increased and wall resistance decreased with decreasing filling rate. Furthermore, leakage eventually occurred below 20 mm. Hg with the lower filling rates. Marked diurnal variations in bladder compliance and wall resistance were observed. Maximum storage capacity was observed at 7 p.m. and the reservoir function subsequently decreased to a plateau between 1 a.m. and 1 p.m.