Urge
Incontinence involves a strong, sudden need to urinate immediately
followed by a bladder contraction, resulting in an involuntary
loss of urine.
Causes, incidence, and risk factors
The ability to hold urine and maintain continence is dependent
on normal function of the lower urinary tract, the kidneys, and
the nervous system -- plus the 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 controlling output) and a stable bladder wall
muscle (detrusor).
The process of urination involves two phases: the filling and
storage phase, and the emptying phase.
During the filling and storage phase, the bladder begins to fill,
stretching to accommodate the increasing amount of urine. The
bladder of an average person can hold 350 mL to 550 mL of urine.
The first sensation of the need to urinate occurs when approximately
200 mL of urine is stored. The nervous system responds by alerting
you to the need to urinate while also allowing the bladder to
continue to fill.
The emptying phase requires the ability of the detrusor muscle
to appropriately contract, forcing urine out of the bladder. The
body must also be able to simultaneously relax the sphincter to
allow the urine to exit.
The bladder of an infant contracts automatically when a certain
volume of urine is collected in the bladder. As the individual
learns to control urination, bladder muscle contraction is prevented
by constant inhibition from the cerebral cortex (part of the brain).
This allows urination to be delayed until the individual is ready.
Undesired bladder muscle contraction may occur as the result
of a break in the neurological pathway from the brain to the bladder.
It can also occur if the bladder is irritated and the normal neurological
impulses to inhibit urination are insufficient to keep the bladder
relaxed as it fills.
Urge
Incontinence is basically a storage problem in which the bladder
muscle contracts 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.
The majority of cases are classified as idiopathic -- 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. It is second only to stress incontinence
as the most common cause of urinary incontinence (involuntary
loss of urine). Approximately 1% to 2% of adult females are affected
by urge
incontinence.
In men, Urge
Incontinence may be due to secondary bladder injuries caused
by benign prostatic hypertrophy (BPH) or bladder outlet obstruction
from an enlarged prostate.
