To develop a noninvasive method to measure urinary flow rate in the mouse. This could be useful for the study of bladder outlet obstruction, as well as processes affecting detrusor function in the awake animal. Genetically engineered mice can improve our understanding of a variety of human bladder diseases.

A metabolic cage without a fecal separation screen was placed above a precision balance that reported the mass of the excreta pan every 100 ms. A computational algorithm identified voids suitable for assessment of uroflow from other excretory events. These algorithms were verified by comparison with a series of images obtained automatically before and during the excretory events. Intraurethral acetic acid was used to induce urethritis and to verify the sensitivity of the measurement technique.

Automatic categorization and characterization of uroflow was successful. Brief exposures of the urethra of the female C57BL6/J mouse to 2% acetic acid decreased uroflow and increased the void duration without a change in the voided volume.

This method will enable studies of urologic function in mice of differing age, sex, strain, and genetic constitution. Murine urethritis can be differentiated from cystitis, known to be associated with a decrease in voided volume. The observed changes were consistent with urethral obstruction induced by local swelling and inflammation.