[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 volume. Furthermore, no clinical relevant technique is available for continuous monitoring of the bladder wall distension respectively bladder volume in paraplegic patients. The presented study investigates the reliability of especially developed implantable ultrasound sensors as a sensoric system for continuous monitoring of the bladder volume. In six anaesthesized pigs two ultrasound sensors, one transmitter and one receiver, were implanted on the bladder wall at different locations (latero-lateral, dorsal-ventral, rostral-caudal). After closing the abdominal wall, the bladder was filled in 50 ml steps up to 250 ml. After each filling step the running time of the ultrasound signal was measured. In all experiments reproducible results and a high correlation of the measured running times with bladder volume were observed. The latero-lateral configuration of the sensors seemed to be most confidential. The presented study indicates that bladder volumetry with implantable ultrasound sensors is possible with minimal technical prerequisites. This promising technique for continuous bladder volumetry could play an important role in the development of an intelligent and autoadaptive neurostimulator of the urinary bladder in paraplegic patients.