BOVINE BLADDER COMPLIANCE INCREASES WITH NORMAL FETAL DEVELOPMENT

In this study we characterized the elastic properties of the normal bo vine bladder throughout fetal life, the newborn period and into adulth ood. The elasticity of the bladder was measured with a novel circularl y clamped bladder testing system. Pressurization of a circularly clamp ed bladder tissue sample caused the tissue to deflect upward repetitiv ely in the shape of a spherical cap. If the centerline deflection is m uch larger than the tissue thickness, the elastic modulus, considered the inverse of compliance, can be determined using linear regression t echniques. The results of our analyses showed that the elastic modulus decreases in direct proportion with increasing gestational age. These data suggest that during normal development of the bovine fetal bladd er there is a progressive change from a rather stiff noncompliant blad der characterized by a high elastic modulus to a compliant bladder wit h a lower elastic modulus. Moreover, the increase in compliance appear s in the developmental period when urine production first occurs. Thes e observations suggest that volume work may be a significant event in the normal development process of the bovine bladder and results in an increase in bladder compliance. Conversely, the poorly compliant feta l bladder may explain some of the transient dilatations of the upper u rinary tract which have been documented in utero. Finally, from the ne wborn period to the mature adult bovine we documented a relatively mod est increase in the elastic modulus or decrease in bladder compliance which may reflect the normal aging process.