Urinary Incontinence Overview
Urine is a waste product made as the kidneys filter the blood. Each kidney (one kidney on each side of the abdomen) sends newly made urine to the bladder through a tube called a ureter. The bladder acts like a storage site for urine. It expands to hold the urine until a person decides to urinate. Incontinence is the involuntary loss of urine or feces; this article will be limited to discussing urinary incontinence.
Holding urine and maintaining continence requires normal function of the renal system as well as the nervous system. Also, a person must be able to sense, understand, and respond to the urge to urinate. The process of urination involves two phases: (1) the filling and storage phase and (2) the emptying phase. During the filling and storage phase, the bladder fills with urine from the kidneys. The bladder stretches as it fills with increasing amounts of urine. A healthy nervous system responds to the stretching of the bladder by signaling the need to urinate, while also allowing the bladder to continue to fill.
Upon urination, the muscle holding the stored urine in the bladder (the sphincter muscle) relaxes, the bladder wall muscle (the detrusor) contracts, and urine passes from the bladder to the outside of the body through another tube called the urethra. The ability to fill and store urine properly requires a functional sphincter muscle to control output of urine from the bladder and a stable detrusor muscle. To empty the bladder completely, the detrusor muscle must contract appropriately to force urine out of the bladder and the sphincter must relax to allow the urine to pass out of the body.
Urinary incontinence is defined by the International Continence Society as involuntary loss of urine that is a hygienic or social problem to the individual. Some define urinary incontinence to include any involuntary loss of urine. According to the Clinical Practice Guideline issued by the Agency for Health Care Policy and Research, there are four different types of incontinence: stress, urge, mixed, and overflow. Some doctors also include functional incontinence as a fifth potential type. The treatment of urinary incontinence varies depending on the specific cause of incontinence.
Medically Reviewed by a Doctor on 9/18/2014
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