Stress incontinence is the involuntary loss of urine upon coughing and sneezing, laughing, exercising or any other activity that puts stress on the bladder. The condition is also known as urethral sphincter incontinence, as it is due to an inability of this sphincter to match the pressure inside the bladder and thus prevent voiding of urine. While men may suffer from the condition, it affects half of all women at some time in their lives, especially in those who have given birth, and though it tends to occur in older women, around a quarter of sufferers are under the age of 30. A number of possible treatments exist, ranging from lifestyle changes and medication to surgical techniques.

Why Does It Happen?

The bladder holds urine, and empties out into the big, wide world via the urethra. The urethra has two sphincters, muscles which prevent urine from being released – the urethral sphincter lies just below the bladder and is the important one with regards to stress incontinence.

Continence of urine depends on the urethral sphincter's ability to oppose the pressure inside the bladder. This is helped by the fact that, at rest, the bladder forms an angle so that the urethra is partially protected from the bladder pressure. This angle disappears upon passing urine, with the bladder forming a funnel with the urethra at its base. Also, the urethral sphincter is usually located within the abdomen so that any increase in abdominal pressure (sneezing, coughing and so on) will squeeze the urethra shut as well as squeezing the bladder.

It is thought that these mechanisms have failed in women with stress incontinence: thanks to damage during childbirth or otherwise, the bladder forms a funnel even when at rest; meanwhile, the urethral sphincter has relocated to within the pelvic floor, and is therefore not squeezed shut when the abdominal pressure increases. This combination of defects means that the pressure in the bladder can easily exceed that of the urethral sphincter during coughs, sneezes, laughing and exercise, thus allowing a small amount of urine to pass each time these activities occur. Weakness of the pelvic floor muscles, which surround the urethra, vagina and rectum, also increases the likelihood of urine escaping.

Why Me?

Stress incontinence is a common phenomenon, and while incontinence pad adverts featuring middle-aged women jumping on trampolines aren't as common as tampon adverts featuring young women playing tennis and cycling, the condition isn't as stigmatising as it used to be. Many women are affected, and there are many factors that may lead to stress incontinence:

• Childbirth. Around 12% of women under 65 who have given birth vaginally have stress incontinence, compared with 7% of those who were delivered by caesarean section and 5% of those who had not given birth. The risk increases with the number of children delivered vaginally, with the majority of women who have given birth to three or more children vaginally developing stress incontinence later in life.

• Age. Following the menopause, a lower level of oestrogen leads the vagina to become drier and thinner, leading to an increased risk of urinary tract infections in some women. Meanwhile, the pelvic floor muscles become weaker. Around a third of women over 80 years have stress incontinence.

• Weight. Being overweight or obese puts more strain on the urethral sphincter, as there is more weight pushing down on the bladder.

• Chronic coughing. Illnesses that lead to a lot of coughing can weaken the pelvic floor muscles.

• Chronic constipation. Attempting to defaecate for long periods of time puts pressure on the pelvic floor muscles and can weaken them.

• Smoking. Smokers often have a chronic cough, and it is thought that the chemicals in smoke may damage the pelvic floor muscles.

• Genetic predisposition. Women with a family history of stress incontinence are more likely to develop it themselves.

• Pelvic surgery. Weakness of the pelvic floor muscles is a rare complication of hysterectomy, caesarean section and other forms of pelvic surgery.

It should be reasonably obvious which of the above factors will affect men. Enlargement or inflammation of the prostate more commonly leads to other forms of incontinence, but stress incontinence is particularly common following pelvic surgery to remove the prostate gland.

Diagnosis

Though stress incontinence is widespread and potentially embarrassing, it's useful to let your doctor know about it, especially if it really bothers you. Some women with stress incontinence will also have urge incontinence, a need to pass urine caused by an unstable bladder, or some other cause of incontinence, and this can require a separate form of treatment. Also, women with weakness of the pelvic floor muscles leading to stress incontinence are at risk of prolapse, in which the bladder, uterus or bowel fall downwards into the vagina.

Stress incontinence is usually easily diagnosed from the symptoms; however, as mentioned, some women have a treatable cause, such as constipation, and others have co-existing urge incontinence. A detailed history and examination of the vagina in women and the back passage in both sexes will help rule out underlying causes of incontinence and may reveal contributory factors. Depending upon your symptoms, there are several tests that can be performed:

• Urinalysis. This involves 'dipping' a urine sample with a testing stick to test for infection and other problems.

• Urinary diary. The doctor may ask you to keep a diary for between three days and a week, detailing the times at which you pass urine, how much urine you pass, and how much fluid you drink.

• Pad test. This involves drinking a set amount of fluid and then performing various tasks that might cause urine to leak in those with stress incontinence. A pad with a waterproof backing is worn throughout, and the change in the pad's weight is used to determine the volume of urine passed.

• Cystometry. This test involves filling the bladder with fluid via a catheter while measuring the pressure in the urethra, bladder and abdomen (via the rectum). This helps differentiate between stress incontinence, where the pressure inside the bladder remains level until it is full, and urge incontinence, where the pressure rises too early, thus leading to the urge to pass urine.

• Video cystometrography. This involves the measurement of pressure as per cystometry, but also includes the introduction of x-ray contrast liquid into the bladder so that it can be viewed using an x-ray machine.

• Uroflowmetry. This test measures how quickly you pass urine, and how much is passed. It uses a measuring device fitted to a toilet and can thus be performed in private.

Dealing With Stress Incontinence

Your doctor may suggest some simple things that may help with stress incontinence: giving up smoking, treating a chronic cough or constipation, exercising regularly, and losing weight if necessary. Post-menopausal women who suffer from recurrent urinary tract infections may benefit from eradication of the infection using long-term antibiotics, and may be offered an oestrogen pessary to treat dryness of the vagina. Pelvic floor exercises are of great help if performed correctly, and are described below. Alternatively, women may use weighted vaginal cones – these are placed into the vagina and held in place by the pelvic floor muscles in a similar manner to a tampon, and women should start with the lightest and work upwards.

A relatively new drug, duloxetine, has been shown to reduce the number of incidences of incontinence. The drug acts by stimulating the pudendal nerve and thus strengthening the urinary sphincter. Unfortunately, the drug is associated with side effects such as a possible risk of liver damage and suicidal tendency, and its role in the treatment of urinary incontinence is in doubt.

Three out of five women will find that the above steps are sufficient to solve their problems; for the other two, surgery is an option that should be carefully considered. The most common operation, colposuspension, is one that lifts the neck of the bladder so that it is within the abdomen – this allows the urethral sphincter to be squeezed shut by abdominal pressure. A less invasive technique involves the use of tension-free vaginal tape (TVT), which is passed around the urethra through two cuts in the abdomen and a third in the vagina, and acts as a sling to support the urethra within the abdomen. Surgery has a 90% success rate in the short term, but only 75% of women are continent of urine six years after the operation. An alternative to surgery in elderly women is the bladder neck support prosthesis, which sits in the vagina and holds up the area surrounding the urethra using two forward-jutting prongs.

Pelvic Floor Exercises

Pelvic floor exercises are sometimes mentioned in women's magazines and may be taught by physiotherapists or continence nurses at your local hospital. They help strengthen the muscles that keep the bladder, vagina and rectum in place, and can be of great help for women with stress incontinence. The exercises may take a little effort at first but are easy to perform and, as they are invisible to the outside world, can be performed anywhere.

The basic exercise takes place when seated, and involves tightening the muscles around the vagina as if trying to pull the genitals up off the seat. This should be held for a good five seconds, and repeated ten times. The same exercise can be repeated when standing, and can be repeated as a series of twenty quick tightenings each lasting a second. The woman can check that she is tightening the correct muscles by inserting a finger into the vagina while performing the exercise – the same method can also be used to test the improvement in muscle strength over a period of a couple of weeks.

The exercises should ideally be repeated for the rest of your life, even after the stress incontinence has been cured. Exercising the pelvic floor will also reduce the risk of stress incontinence and of prolapse following childbirth, and should be practised by all women following pregnancy.