Bladder Emptying: Contractility

Abstract

Bladder contractility is a term used to describe the strength of bladder detrusor muscle contractions [1,2]. Since bladder contraction requires parasympathetic stimulation, the detrusor pressure depends on the inherent strength of the detrusor muscle itself, which can be affected by a variety of factors, and intact neural circuitry. Loss of either would clearly impact contractile strength and overall bladder function. Normal detrusor function is initiated by a drop in urethral pressure followed by a continuous detrusor contraction which leads to complete bladder emptying within a normal time span. For many women who void primarily by urethral relaxation, this contraction may be modest or even absent. Detrusor underactivity implies a detrusor contraction of reduced strength and/or duration resulting in prolonged voiding, and/or a failure to achieve complete bladder emptying. An acontractile detrusor identifies the condition where no detrusor contraction is noted, also typically associated with prolonged voids, incomplete emptying, or inability to void altogether. Examples of each of these conditions are demonstrated in urodynamic tracings shown in the remainder of the chapter.Other factors, such as outlet resistance, can also greatly affect bladder contractility. Enhanced outlet resistance, in the setting of bladder outlet obstruction, will result in increased detrusor force for a variable period of time, followed potentially by a loss of force depending on the severity and duration of obstruction. Similarly diminished outlet resistance, for example in the setting of stress urinary incontinence, has been shown to result in lowered detrusor pressures during voiding.