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Urinary incontinence (UI) is involuntary leakage of urine. Urine is produced in the kidneys and stored in urinary bladder. Urination is the process of emptying the bladder through the urethra that connects the urinary bladder to the external urethral orifice. There are two sphincters (valves) that keep the urethra closed to prevent leak: internal urethral sphincter located at the neck of the bladder, and external urethral sphincter located below the prostate gland and is supported by the pelvic floor muscles (See Fig. 1).
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Fig.1: Anatomy of male urinary organs. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
When the bladder is full, stretch receptors in the wall of the bladder send a signal to the spinal cord and the brain. At times when it’s not appropriate to urinate, the brain sends back an inhibitory signal to keep the sphincters closed and prevent voiding. When you wish to urinate, this inhibition is removed, the spinal cord instructs the muscle of the bladder (detrusor muscle) to contract and the sphincters to open to let the urine out (Fig. 2).
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Fig.2: Neural control of urine voiding. Sensory nerve sends the signal from the full bladder to the nervous system; motor nerve brings instruction from the nervous system to the muscles. See text for more details. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Causes of urinary incontinence
– Problems with the nervous system: stroke, multiple sclerosis, Pakinson’ s disease and spinal cord injuries may affect the neural control loop illustrated in Fig.2 and cause incontinence.
– Weakness of sphincters, or lack of support from underneath muscles (muscles of the pelvic floor) making the sphincters weak so they can not close properly.
– Blocked or narrowed urethra, weakness of bladder muscles: bladder can not empty, urine builds up and leaks.
Types of urinary incontinence in men and typical cause of each type
1. Stress incontinence: urine leakage while sneezing, coughing, laughing or any activity that creates abdominal pressure on the bladder. This usually occurs because the muscles or tissues underneath the bladder are weakened and can no longer support it. In men, this typically happens after the prostate gland is removed for reasons such as prostate cancer.
2. Urge incontinence: need to void that can not be deferred, inability to hold. This is commonly caused by overactive bladder, a condition in which muscles in the wall of the bladder contract in an uncontrollable manner. The reason why this happens is unclear but it’s likely to involve problems in the nervous system.
3. Overflow incontinence: constant dribbling of urine. This happens when the bladder does not empty properly while voiding making it almost always full and urine overflows. This is due to weak detrusor muscle in the bladder wall or a blocked/narrowed urethra. In men, the major cause for this type of incontinence is a condition called enlarged prostate or benign prostate hyperplasia (BPH) . Click on the link to read more about this condition.
Fig.3: Types of urinary incontinence in men and typical cause in each case. The prostate gland (orange color) is located under the bladder where it wraps around the first part of the urethra. See text for more details. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
