Noninvasive monitoring of lower urinary tract dysfunction in rats with bladder outlet obstruction using uroflowmetry and ultrasonography.

Abstract

PURPOSE: This study aimed to characterize the time-dependent changes in lower urinary tract function in a rat model of partial bladder outlet obstruction (BOO) using noninvasive techniques, including uroflowmetry and ultrasound imaging. METHODS: Eight-week-old male rats underwent partial ligation of the urethra to induce BOO. Voiding behavior was assessed preoperatively and at 1, 2, and 4 weeks postoperatively using metabolic cages. Urine flow rate was calculated based on changes in voided volume over time. Average flow rate, maximum flow rate, and voiding time were derived from these metabolic cage data. Bladder capacity and wall thickness were evaluated by high-resolution ultrasonography. RESULTS: Voiding frequency significantly increased at 1, 2, and 4 weeks compared to preoperative values. Mean voided volume per micturition was significantly reduced at 2 weeks. Urinary flow curves showed a sawtooth-like pattern, suggestive of external urethral sphincter bursting that is a characteristic of rat voiding. The maximum flow rate significantly decreased at 1 week postoperatively and remained reduced through 4 weeks. Mean flow rate was significantly decreased at 2 weeks, while voiding time showed a tendency to increase, although the difference was not statistically significant. Ultrasonography revealed significant increases in maximum bladder volume at 2 and 4 weeks and in anterior bladder wall thickness at 4 weeks. CONCLUSIONS: This study demonstrated the feasibility of noninvasively monitoring time-dependent changes in rats with BOO. These findings could be extrapolated to the pathophysiological process during the bladder compensation phase in human BOO.