This distressing and common condition can be the source of much embarrassment. The causes are many and most are not serious and are capable of cure or effective management.
Control of the Bladder
The bladder collects urine from the kidney and stores it until it is appropriate for it to be passed. Urine enters the bladder via two ureters, one from each kidney. When the bladder is full a reflex action is triggered and the bladder empties via the urethra.
This reflex action is under the control of the autonomic (automatic) nervous system and causes the detrusor muscle of the bladder to contract and the inner bladder sphincter (situated at the neck of the bladder) to relax and allow the urine to flow out.
If this were the whole story we would all be incontinent. There is an external sphincter in the urethra which is normally, in almost everyone other than young infants, under voluntary control. Signals from the full bladder travel to the brain and give the sensation of wanting to pass urine. If it is appropriate the external sphincter is released, the bladder muscle contracted and urine is passed. Anything which interferes with this complex system of neuromuscular control can lead to urinary incontinence.
Causes of Incontinence
These fall into three major categories: Malfunction of the nervous control of the bladder, weakness of bladder muscles and or surrounding tissues, and localised obstruction in or around the urinary tract.
Malfunction of Nervous Control
This can be due to physical or psychological reasons. Any disease which damages nerve cells can affect control of the bladder.
- Brain or spinal cord damage: conditions such as multiple sclerosis and Alzhiemer's disease and spinal injury can all produce incontinence either due to impaired awareness of a full bladder or loss of neuromuscular control of the bladder and its sphincters.
- Urge incontinence: having the desire to pass urine which is then followed shortly afterwards by uncontrolled voiding of urine. Can be due to local irritation from bladder tumours or infections. It can also occur with brain and spinal cord disease. Sometimes it is triggered simply by hearing running water. In such cases no disease process is normally found.
- Enuresis: this is bed wetting, which starts in childhood but sometimes extends into adulthood. It can result from organic disease but in most cases the cause is thought to be psychological. Often responds to bladder training.
Muscular Weakness
- Stress Incontinence: the involuntary passage of urine when coughing, laughing or lifting. Due to laxity of muscles in and around the bladder (pelvic floor muscles). More common in women after childbirth, usually responds to pelvic floor exercises, occasionally surgery required.
- Incontinence in the elderly: probably due to a combination of weak muscles and poor functioning nervous control. Very common but responds well to specific exercises.
Obstruction in or Around the Bladder
Obstructions by tumours, enlarged prostate or stones can result in overflow incontinence. Usually evident by small amounts of urine leaking at night.
This article is for information only. If you have any health concerns you should consult your doctor.
Resources
Essential Medicine eds.Read and Vann Jones Pub. Churchill Livingstone 1998
A Dictionary of Symptoms by Joan Gomez Pub. Granada Books
An Introduction to Human Physiology by Green. Pub. Oxford University Press.
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