A new method of noninvasively measuring bladder leak point pressure in female rats

Stress urinary incontinence is diagnosed by decreased leak point pressure (LPP), the bladder pressure at which urine leaks from the bladder. The authors have developed a method to measure LPP in animals. The purpose of this project is to test a device for noninvasive measurement of LPP against the authors´ standard invasive method of LPP testing in rats. Four female rats underwent suprapubic bladder catheter implantation. Two days later, the bladder was filled with saline to 1/2 capacity. Pressure was applied to the abdomen while bladder pressure was measured. Pressure was increased until saline leaked from the urethra, to measure LPP. A platform on a force transducer allowed the authors to measure the externally applied force. The study was repeated with the platform of the device over the abdomen. The force was increased until saline leakage occurred. When abdominal pressure was increased in the absence of the device, bladder pressure increased in 7.2±1.1s to a LPP of 32.5±6.7 cmH₂O, giving an increase in bladder pressure of 27.2±7.3 cmH₂O from baseline. These values were not significantly different from the duration (5.2±0.7s), LPP (42.2±10.6 cmH₂O), or increase in bladder pressure (30.1±12.5 cmH₂O) measured when both force and pressure were recorded, indicating repeatability of the experiment. A linear regression fit to bladder pressure v. force data demonstrated linearity in most cases. Thus, the authors have demonstrated ease of use, repeatability, and reliability of a new device for noninvasively measuring leak point pressure in laboratory rats