Continuous uroflow cystometry in the urethane-anesthetized mouse

In vivo animal cystometry represents an accepted methodology for the study of lower urinary tract physiology. A particular advantage of the mouse model is the availability of genetically modified strains, offering the possibility of linking individual genes to relevant physiological events. However, small voided volumes complicate the ability to obtain reliable pressure-flow data by gravimetric methods, due to non-continuous drop formation and release during voiding. We investigated the feasibility of a simple non-gravimetric continuous urine collection system during cystometry under urethane anesthesia, and compared urethane-anesthetized with awake cystometry.

Cystometry was performed in awake and urethane-anesthetized female mice using a suprapubic tube. A simple, novel non-gravimetric method of urine collection was used in urethane-anesthetized animals to assess voided volume and permit flow rate calculations. Pressure and time-related variables were compared between groups.

Voided urine collection appears to be complete and continuous in this model. Mean voided volume was 0.09 ± 0.020 ml, with an average flow rate of 0.029 ± 0.007 ml/sec. Urethane anesthesia delayed cystometric pressure/volume responses. However, micturition reflexes were intact and otherwise comparable between groups. Female mice void with pulsatile pressurization previously described in rats.

Suprapubic voiding cystometry using a simple and reliable urine collection method under urethane anesthesia is feasible in mice, permitting the integration of voided volumes with pressure and time data. The inclusion of volume and flow data enhances the usefulness of the mouse model for in vivo assessment of detrusor and potentially sphincteric performance.