Step-wise cystometry of urinary bladder. New dynamic procedure to investigate viscoelastic behavior.

Step-wise cystometry has been developed to analyze the pressure-relaxation phenomena of the bladder in mongrel dogs. The results show that a mathematical model consisting of two exponentials and a constant can befitted to the measurements. This model is interpreted in a mechanical model of the bladder wall in terms of viscoelasticity. Recent advances in urodynamics have indicated that to understand better the results of urodynamic investigations, it is necessary to have more information about the mechanical properties of the bladder wall. For example, the properties of the wall can affect the storage capacity and the expulsion-force of the bladder. While the storage-(adaptation) properties formerly were ascribed exclusively to active mechanisms, we now cannot exclude that passive mechanisms are also involved. Qualitatively the same behavior was found in the bladder, in vitro, several hours after death and even in rubber bal1oons.l In this report we describe the over-all behavior of the bladder in terms of viscoelasticity and geometry of the bladder.