Urge incontinence involves a strong, sudden need to urinate, followed by a bladder contraction, which results in leakage.

A person's ability to hold urine and maintain continence depends on normal function of the lower urinary tract, the kidneys, and the nervous system. The person must also have a physical and psychological ability to recognize and appropriately respond to the urge to urinate.

The bladder's ability to fill and store urine requires a functional sphincter muscle (which controls the flow of urine out of the body) and a stable bladder wall muscle (detrusor).

The process of urination involves two phases:

• Filling and storage
• Emptying

During the filling and storage phase, the bladder stretches so it can hold the increasing amount of urine. The bladder of an average person can hold 350 mL to 550 mL of urine. Generally, a person feels like they need to urinate when approximately 200 mL of urine fills up in the bladder. The nervous system tells you that you need to urinate, and also allows the bladder to continue to fill.

The emptying phase requires that the detrusor muscle contract, forcing urine out of the bladder. The sphincter muscle must relax at the same time, so that urine can flow out of the body.

The bladder of an infant automatically contracts when a certain volume of urine is collected in the bladder. As the child grows older and learns to control urination, part of the brain (cerebral cortex) helps prevent bladder muscle contraction. This allows urination to be delayed until the person is ready to use the bathroom.

Undesired bladder muscle contractions may occur from neurological problems and bladder irritation.

URGE INCONTINENCE

Urge incontinence is leakage of urine due to bladder muscles that contract inappropriately. Often these contractions occur regardless of the amount of urine that is in the bladder. Urge incontinence may result from neurological injuries (such as spinal cord injury or stroke), neurological diseases (such as multiple sclerosis), infection, bladder cancer, bladder stones, bladder inflammation, or bladder outlet obstruction.

In men, urge incontinence may be due to neurologic disease or bladder changes caused by benign prostatic hypertrophy (BPH) or bladder outlet obstruction from an enlarged prostate.

The majority of cases of urge incontinence are idiopathic, which means a specific cause cannot be identified.

Although urge incontinence may occur in anyone at any age, it is more common in women and the elderly.

• Sudden and urgent need to urinate (urinary urgency)
• Frequent urination, in the daytime and at night
• Abdominal distention or discomfort
• Involuntary loss of urine

A physical examination will include examination of the abdomen and rectum. Women will also have a pelvic exam. Men will also have a genital exam. In most cases the physical exam reveals nothing abnormal.

If there are neurologic causes, other neurologic abnormalities may be found.

Tests include the following:

• Post-void residual (PVR) to measure amount of urine left after urination
• Urinalysis or urine culture to rule out urinary tract infection
• Urinary stress test (the patient stands with a full bladder and coughs)
• Pad test (after placement of a pre-weighed sanitary pad, patient exercises, then pad is weighed to determine urine loss)
• Pelvic or abdominal ultrasound
• X-rays with contrast dye
• Cystoscopy (inspection of the inside of the bladder)
• Urodynamic studies (measurement of pressure and urine flow)
• EMG (myogram) - rarely needed

Further tests will be performed to rule out other types of incontinence. These tests may include the "Q-tip test," which measures the change in the angle of the urethra at rest and when straining. An angle change of greater than 30 degrees often indicates significant weakness of the muscles that support the bladder, which is common in stress incontinence.