Urinary bladder volume tracking using a Kalman filter

This study introduced the Kalman filter procedure for tracking urinary bladder filling from intermittent bladder volume measurements taken by an ultrasonic bladder volume monitor. The Kalman filter was based on a double integrator as a model for the bladder filling process between micturitions and included a procedure to reset the filter in the event of a micturition. The performance of the Kalman filter was evaluated experimentally using an ultrasonic bladder volume monitor on seven male urologic patients. During cystometry, saline was infused into the patient's bladder at a constant rate of 30 ml min(-1) until it was full, and the volume of the bladder was recorded every 30 s by the bladder volume monitor. The evaluation showed that the filter significantly improved the precision of the measured volumes in terms of mean absolute errorby 4.2 ml (95% confidence interval: 0.7-7.7 ml) (p = 0.025) without affecting the system accuracy, i.e. slope (p= 0.92) and intercept (p= 0.32). Finally, the micturition reset procedure was verified using simulated data.