Radiotelemetered cystometry in pigs: validation and comparison of natural filling versus diuresis cystometry

PURPOSE: Cystometry has previously been performed in awake animals using vesical and abdominal catheters, and artificial bladder filling. Conventional urodynamic recordings may be obtained in this manner, albeit under nonphysiological and potentially stressful conditions. Therefore, we developed a technique to perform continuous, ambulatory cystometric monitoring in pigs. MATERIALS AND METHODS: A dual pressure radiotelemetry device was surgically implanted in 22 large white pigs. Vesical and abdominal pressures were recorded and validated, subtracted detrusor pressures were derived and natural fill and diuresis cystometry was compared. RESULTS: Continuous recordings were obtained for 1 to 24 hours, and the devices remained in the animals for up to 3 months. There were few complications and incrustation of the intravesical catheter tip occurred but it did not appear to affect recorded pressures. The pressure data were validated by comparison with filling pressures during bladder distention and simultaneous conventional cystometry at the end of the experimental period. Comparison of natural filling and diuresis cystometrograms showed that natural bladder filling results in higher maximum detrusor pressure during voiding (38.1 versus 33.9 cm. H2O, p <0.05), higher detrusor pressure after contractions (42.6 versus 32.2 cm. H2O, p <0.05) and more frequent detection of unstable contractions in pigs with detrusor instability secondary to experimental manipulation of the lower urinary tract (77.8% versus 45.0%, p <0.05). CONCLUSIONS: This technique allows continuous cystometric monitoring in less stressed animals under more physiological conditions for relatively long periods and, thus, allows prolonged assessment of bladder function in pigs in response to pathological and pharmacological manipulations. Nonphysiological rates of bladder filling have been shown to result in detrusor inhibition, which emphasizes the importance of ambulatory cystometry when describing bladder function.