Minipig model for the study of voiding parameters in the conscious state and natural posture: normal urodynamic profiles.

OBJECTIVE

To provide baseline data on an animal model in which collecting and voiding can be accurately characterized urodynamically in the conscious state and natural posture.

METHODS

Thirty-one female Yucatan microswines (age 4-8 months, weight 11-43 kg) were used. Portcatheters were placed in the bladder and peritoneal cavity, and reservoirs were implanted under the back skin for easy access. For urodynamic study, conscious pigs were restrained in specially designed adjustable cages. The portcatheter reservoirs were connected by 20-gauge needles and tubings to a UDS-120 digital computer polygraph to measure the total bladder pressure (pves) and abdominal pressure (pabd). A flow meter was placed behind and underneath the animal to measure the uroflow. Diuresis was induced with furosemide, and 2-4 voiding cycles were monitored. Isovolumetric detrusor pressure (pdet, isv) was obtained in the last cycle by manual interruption of flow per vagina. Urodynamic investigations were performed satisfactorily in all animals.

RESULTS

The voided volume was 102-340 ml (mean 181.7 +/- 11.9 ml). Seven pigs had residual urine (4-39 ml, mean 14.3 +/- 4.7 ml). The initial opening pressure at the start of voiding was 19.9 +/- 1.5 cmH2O; detrusor pressure at maximum flow rate was 15.7 +/- 1.3 cmH2O; average flow was 12.6 +/- 0.7 ml/s; maximum flow rate was 20.7 +/- 1.1 ml/s; pdet, isv was 51.6 +/- 2.4 cmH2O; flow time was 15.9 +/- 1.2 seconds; mean resistance factor (R) was 0.06 +/- 0.01 cmH2O ml-2s2; mean urethral resistance factor (URA) was 7.10 +/- 0.51 cmH2O; and mean strength of voiding detrusor contraction was 3.91 +/- 0.20 W/m2.

CONCLUSION

The above model allows reliable measurement of pressure-flow parameters in the conscious state and natural posture, permitting in-vivo urodynamic characterization of obstructive voiding dysfunction and correlation with detrusor structure.