Pressure-monitoring catheters will be inserted into your bladder and rectum, and your bladder function will be checked as the bladder is slowly filled with fluid. Measurements will then be made of your bladder capacity (the volume of urine the bladder can hold), bladder and abdominal (stomach) pressures, and bladder compliance (the bladder's ability to hold urine) throughout the course of this study. This procedure will take about 90 minutes to complete.