Mechanical Properties and Functions of the Urianry Bladder II. Mechanical Properties of the Bladder Evaluated by Cystometrogram as a Urine Reservoir and in Expulsion

Abstract

Cystometry may be considered as a stretch test for the bladder wall. In the 1st report, it was stated that the properties of the bladder were well explained as a visco-elastic model proposed by Glantz and a formula for the stress-strain curve was proposed. In this 2nd report, another formula representing theoretical cystometrogram derived from the former formula, is proposed. Using this formula, the three constants (α, β, γ) of a normal living bladder, extirpated bladder and pelvic nerve-cutting bladder were calculated by computer analysis. They corresponded well to those obtained from the actual stress-strain curve of the bladder. Thus one can obtain these constants by computer analysis from an ordinary clinical cystometrogram without performing stretch test of the bladder. The three constants in the formula at voiding were also calculated by the same computer analysis of voiding cystometrogram. Among the three, only the proportional stiffness (α) elevated 10 times higher at bladder contraction than that at relaxation. This fact suggests that the bladder can void automatically by its mechanical properties, when the proportional stiffness (α) is changed by the switching of nerve stimulation. The detailed theory on the formula will be published in English elsewhere. © 1991, THE JAPANESE UROLOGICAL ASSOCIATION. All rights reserved.