Urinary (or bladder) incontinence is when you are not able to keep urine from leaking from your urethra, the tube that carries urine out of your body from your bladder. It can range from an occasional leakage of urine, to a complete inability to hold any urine.

The three main types of urinary incontinence are:

• Stress incontinence -- occurs during certain activities like coughing, sneezing, laughing, or exercise.
• Urge incontinence -- involves a strong, sudden need to urinate followed by instant bladder contraction and involuntary loss of urine. You don't have enough time between when you recognize the need to urinate and when you actually do urinate.
• Overflow incontinence -- occurs when the bladder cannot empty completely, which leads to dribbling.
• Mixed incontinence -- involves more than one type of urinary incontinence.

Bowel incontinence, a separate topic, is the inability to control the passage of stool.

Incontinence is most common among the elderly. Women are more likely than men to have urinary incontinence.

Infants and children are not considered incontinent, but merely untrained, up to the time of toilet training. Occasional accidents are not unusual in children up to age 6 years. Young (and sometimes teenage) girls may have slight leakage of urine when laughing.

Nighttime urination in children is normal until the age of 5 or 6.

NORMAL URINATION

Normally, the bladder begins to fill with urine from the kidneys. The bladder stretches to allow increasing amounts of urine.

The first urge to urinate occurs when around 200 mL (just under 1 cup) of urine is stored in the bladder. A healthy nervous system will respond to this stretching sensation by alerting you to the urge to urinate, while also allowing the bladder to continue to fill.

The average person can hold around 350 to 550 mL (more than 2 cups) of urine. Two muscles help control the flow of urine:

• The sphincter (the circular muscles around the opening of the bladder) must be able to squeeze to prevent urine from leaking.
• The bladder wall muscle (detrusor) must stay relaxed so the bladder can expand.

When it is time to empty the bladder, the bladder wall (detrusor) muscle contracts or squeezes to force urine out of the bladder. Before this muscle squeezes, your body must be able to relax the sphincter to allow the urine to pass out of the body.

The ability to control urination depends on having normal anatomy, a normally functioning nervous system, and the ability to recognize and respond to the urge to urinate.

Causes include:

• Problems with the anatomy
• Blockage
• Brain or nerve problems
• Nerve and muscle disorders (neuromuscular disorders)
• Dementia or other psychological problems that affect the ability to recognize and respond to the urge to urinate

Incontinence may be sudden and temporary, or ongoing and long-term. Causes of sudden or temporary incontinence include:

• Bedrest -- for example, when recovering from surgery
• Certain medications (such as diuretics, antidepressants, tranquilizers, some cough and cold remedies, and antihistamines for allergies)
• Mental confusion
• Pregnancy
• Prostate infection or inflammation
• Stool impaction from severe constipation, causing pressure on the bladder
• Urinary tract infection or inflammation
• Weight gain

Causes that may be more long-term:

• Alzheimer's disease
• Bladder cancer
• Bladder spasms
• Depression
• Large prostate in men
• Neurological conditions such as multiple sclerosis or stroke
• Nerve or muscle damage after pelvic radiation
• Pelvic prolapse in women -- falling or sliding of the bladder, urethra, or rectum into the vaginal space, often related to having had multiple pregnancies and deliveries
• Problems with the structure of the urinary tract
• Spinal injuries
• Weakness of the sphincter, the circular muscles of the bladder responsible for opening and closing it; this can happen following prostate surgery in men, or vaginal surgery in women