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Urge incontinence
Definition:
Urge incontinence involves a strong, sudden need to urinate immediately followed by a bladder contraction, resulting in an involuntary loss of urine. Alternative Names:
Overactive bladder; Detrusor instability; Detrusor hyperreflexia; Irritable bladder; Spasmodic bladder; Unstable bladder; Incontinence - urge
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Causes, incidence, and risk factors:
The ability to hold urine and maintain continence is dependent on normal function of the lower urinary tract, the kidneys, and the nervous system -- plus the physical and psychological ability to recognize and appropriately respond to the urge to urinate. The bladder's ability to fill and store urine requires a functional sphincter (muscle controlling output) and a stable bladder wall muscle (detrusor). The process of urination involves two phases: the filling and storage phase, and the emptying phase. During the filling and storage phase, the bladder begins to fill, stretching to accommodate the increasing amount of urine. The bladder of an average person can hold 350 mL to 550 mL of urine. The first sensation of the need to urinate occurs when approximately 200 mL of urine is stored. The nervous system responds by alerting you to the need to urinate while also allowing the bladder to continue to fill. The emptying phase requires the ability of the detrusor muscle to appropriately contract, forcing urine out of the bladder. The body must also be able to simultaneously relax the sphincter to allow the urine to exit. The bladder of an infant contracts automatically when a certain volume of urine is collected in the bladder. As the individual learns to control urination, bladder muscle contraction is prevented by constant inhibition from the cerebral cortex (part of the brain). This allows urination to be delayed until the individual is ready.
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