Volumetry of the urinary bladder with implantable ultrasound sensors

Experimental studies revealed that the contractile response of the urinary bladder to sacral anterior root stimulation depends on the actual bladder v olume. Furthermore, no clinical relevant technique is available for continu ous monitoring of the bladder wall distension respectively bladder volume i n paraplegic patients. The presented study investigates the reliability of especially developed implantable ultrasound sensors as a sensoric system fo r continuous monitoring of the bladder volume. In six anaesthesized pigs tw o ultrasound sensors, one transmitter and one receiver, were implanted on t he bladder wall at different locations (laterolateral, dorsal-ventral, rost ral-caudal). After closing the abdominal wall, the bladder was filled in 50 mi steps up to 250 ml. After each filling step the running time of the ult rasound signal was measured. In all experiments reproducible results and a high correlation of the measured running times with bladder volume were obs erved. The laterolateral configuration of the sensors seemed to be most con fidental. The presented study indicates that bladder volumetry with implant able ultrasound sensors is possible with minimal technical prerequisites. T his promising technique for continuous bladder volumetry could play an impo rtant role in the development of an intelligent and auto-adaptive neurostim ulator of the urinary bladder in paraplegic patients.