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| What causes urinary incontinence? |
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Reviewed by Dr Hilary McPherson, consultant obstetrician and gynaecologist and Dr Kate Patrick, specialist registrar
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Stress urinary incontinence (SUI)
It's thought SUI is due to weakness in:
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the pelvic floor muscles that support the organs in your pelvis and abdomen
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the sphincter muscle that keeps the bladder outlet closed.
If they aren’t strong enough to support your bladder, the sphincter opens slightly and urine leaks out.
This means you’re more likely to leak urine when there’s any extra pressure on your abdomen and bladder, for example when you exercise, cough, sneeze or laugh.
Medication such as diuretics don’t cause stress urinary incontinence, but they can make it worse.
The most common causes of SUI are:
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pregnancy - carrying the increasing weight of baby in your pelvis over 40 weeks puts extra stress on your pelvic floor.
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childbirth - if you have a vaginal delivery, it’s possible the nerves around your pelvic floor become stretched and bruised. After delivery, they can’t make the pelvic floor work properly and the muscles may not respond as well.
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pelvic surgery - a hysterectomy is an operation to remove the womb (uterus). It can cause damage to the pelvic floor.
Other factors can contribute to your risk of developing SUI. Obesity, constipation and the chronic cough caused by smoking all increase pressure on the pelvic floor. Hormonal changes after the menopause can also affect the pelvic floor.
Urge urinary incontinence (UUI)
Urge urinary incontinence is thought to be caused by overactivity of the bladder wall (also known as the detrusor muscle).
It can also be caused by:
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medical conditions, such Alzheimer's, stroke, dementia, diabetes or multiple sclerosis. In these cases, the nerve passages along the path from your bladder to your brain are damaged, so you get a strong bladder contraction and can’t stop it.
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smoking. A study by Dallosso et al in 2002 found that smokers were nearly one and a half times more likely to develop an overactive bladder than non-smokers, possibly caused by the effect of nicotine on the detrusor muscle.
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being overweight.
Infections, constipation
and the side-effects of some medication can temporarily cause urge urinary incontinence.
Mixed urinary incontinence (MUI)
Some of the causes of SUI and UUI are similar, for example smoking and being overweight, so lifestyle changes can help both conditions.
The effect of fluids
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Large fluid intake: if you drink more than 1500ml a day, it’s likely to make SUI worse because the volume of the bladder increases and puts more pressure on the pelvic floor. It also makes UUI worse because you pass smaller amounts of urine more frequently.
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Not enough fluids: cutting down too much will make your urine more concentrated, which irritates your bladder and makes UUI worse. It also decreases the effective capacity of your bladder, again making UUI worse.
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Caffeinated drinks: caffeine is a diuretic, which makes your kidneys make more urine, so you pass more water. Caffeine also irritates the detrusor (bladder) muscle. Tea, coffee and cola all contain caffeine.
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Carbonated drinks: if you drink carbonated drinks daily, you’re more likely to have SUI and UUI. This is possibly because the most popular carbonated drinks are colas, which contain caffeine and citric acid.
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Alcohol: alcohol is a diuretic and stimulates your kidneys to produce more urine, which will worsen urinary incontinence.
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References
Dallosso et al: HM Dallosso, CW McGrother, RJ Matthews & MMK Donaldson, The association of diet and other lifestyle factors with overactive bladder and stress incontinence: a longitudinal study in women. BJU International 2003 92 (1), 69.
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Based on a text by Dr Dan Rutherford, GP
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Last updated 11.11.2005
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