The study of urinary incontinence has revealed two main types of incontinence.

The commonest is called stress incontinence - when the bladder sphincter just gives way under pressure and a small amount of urine escapes on straining, for example when coughing, laughing, sneezing or doing physical exercise.

In severe cases it can happen while walking or when getting up from a sitting position. Stress incontinence is usually the result of weakening of the muscles in the pelvic floor that surround the bladder. This often happens during pregnancy, following childbirth or after the menopause.

The second type of urinary incontinence is called urge incontinence. This happens when the urge to pass urine becomes overwhelming and urine is passed before a toilet can be reached. Urge incontinence is caused by the bladder sending a message to the brain that it is full, often too early and the bladder muscle starts to contract too early (also called bladder instability).

This may be caused by cystitis (urinary infection) or an overactive or unstable bladder, which can sometimes be related to nerve problems including stroke, dementia, multiple sclerosis, or spinal cord injury.

The two types may occur together, but treatment is quite different.

Incontinence can also be associated with narrowings (strictures) of the urethra.

Incontinence can also be caused as a side effect of some kinds of drugs or medicines.