Measurement of Bladder Volume Using an Implantable Volume Sensor in Rats

Lee, Dong Sup; Kim, Su Jin; Sohn, Dong Wan; Yoo, Je Mo; Choi, Bum Kyu; Lee, Moon Kyu; Lee, Seung Joon; Kim, Sae Woong

Abstract

PURPOSE
Real-time monitoring of urinary bladder volume can not only provide information on urinary bladder function more precisely in laboratories and in the setting of intravesical pressure monitoring, but can also help areflexic neurogenic bladder patients have notice of the timing for optimal urination to prevent secondary complications. Thus we introduce a new implantable bladder volume monitoring device and its usefulness.
MATERIALS AND METHODS
Ten male Sprague-Dawley rats were used under intraperitoneal anesthesia. Two microelectrodes produced by a micro-electrical-mechanical systems (MEMS) process were stitched onto each side wall of the urinary bladder and 25 G needles were inserted through the bladder dome. The distances between two microelectrodes converted from capacitances recorded by LCR meter were monitored in real-time during cystometry. Urinary bladder volume was estimated with its shape approximated as a sphere.
RESULTS
Estimated bladder volume correlated well statistically with infused volume in (p<0.05 regression analysis). Since the urinary bladder was filled with over 0.6 cc normal saline in each rat, estimated urinary volume was not different than infused saline volume (p>0.05, repeated measures ANOVA).
CONCLUSIONS
In our animal model, an implantable volume-monitoring device produced reliable data. Therefore, we expect that it should be an excellent tool for detecting urinary bladder volume and producing more accurate and useful information during urodynamic laboratory studies with small animals. Furthermore, we expect that this study will be the foundation of research for the clinical application of bladder volume monitoring devices to areflexic neurogenic bladder patients.