A Conductance-Based Sensor to Estimate Bladder Volume in Felines.

New research tools are essential to help understand the neural control of the lower urinary tract (LUT). A more nuanced understanding of the neuroanatomy of bladder function could enable new treatment options or neuroprosthesis to eliminate incontinence. Here we describe the design, prototyping and validation of a sensing mechanism for a catheter-free fluid volume estimating system for chronic neurophysiological studies of the lower urinary tract and ambulatory urodynamics. The system consists of two stimulation electrodes, one sensing anode, and a microcontroller for control and recording. The packaged device is small enough to be surgically implanted within the bladder lumen, where it does not inhibit bladder function nor inflict trauma. Benchtop evaluation of the conductance-sensing system in simulated bladder-like conditions has demonstrated that the system can predict intra-vesical fluid volume with $< 5$ mL mean error below 40mL and worst-case mean error of 13mL near full-scale volume. These results indicate that conductance-based volume sensing of the urinary bladder is a feasible method for real-time measurement.