The Basic Science Behind Practical/Clinical Urodynamic Analysis
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While the purpose of the lower urinary tract seems simple, to store and periodically release urine, the physiological control of these functions is quite complex. Normal lower urinary tract function depends on finely coordinated active contraction and active relaxation of different smooth muscle layers across the bladder-urethral unit, with opposing activity states depending on the phase of the micturition cycle (i.e. filling vs. voiding), and governed by the two limbs of the autonomic nervous system. An additional level of storage assurance is afforded by the somatomotor system that controls the rhabdosphincter. All of these are regulated by reflexes organized at the sacral and thoracolumbar spinal cord and the brainstem, with an overlay of conscious (coritcal) control to insure environmental appropriateness of voiding.
Our best tools to directly query the health of this system are urodynamic tests. In order to understand our measurements and their meanings, it is important to understand the anatomy, physiology and biomechanics of the system and the physics behind the measurements. This chapter will provide an overview of these important concepts as a scientific base for the subsequent chapters.
KeywordsUrodynamics Fluid dynamics Cystometry Bladder Urethra Lower urinary tract Biomechanics Physiology Tissue mechanics