Urinary Incontinence
P.K.Ghatak, MD
Urinary incontinence is the medical term for leakage of urine; the common expression is wetting the underpants or simply an accident.
In children, voiding is brought under control several months (between 12 and 30 months) after birth, about the time the baby learns to walk independently. The nerve fibers in certain areas have delayed myelination. Myelin is a fatty substance that gives the nerve fibers a coat of insulation so the nerve impulse from the center/brain can reach the intended organs/ tissues and not allowed to short out on the way.
The urinary bladder has both involuntary and voluntary muscles. At the apex of the urinary bladder, at the point where the urethra (a tube that carries urine) begins, there is an involuntary muscular sphincter that must relax to permit the urine to flow out of the urinary bladder. Another muscular sphincter, which is made up of voluntary muscles, is present just after it emerges from the pelvic floor, and is called the external sphincter. It is under voluntary control of the Pudendal nerves. It keeps the external sphincter closed until the time to void. It works by withdrawing inhibition and producing contraction of voluntary muscles.
Nerve controlling the urinary bladder.
Three sets of nerves innervate the urinary bladder. Sympathetic, parasympathetic and somatic nerves. Stimulation of the sympathetic nervous system produces holding of urine, the parasympathetic nerve is the nerve of evacuation of urine. Pudendal nerves are the final arbitrator either to void or to hold urine and are totally under voluntary control.
The lumber segment of the spinal cord supplies the sympathetic fibers to the inferior hypogastric ganglion and the hypogastric nerve carries the impulse to the bladder and internal sphincter. Sacral 1 and sacral 2 segments supply parasympathetic fibers to the parasympathetic ganglion, which supply the postganglionic fibers to the bladder and internal sphincter.
Anterior horn cells of the sacral 1 and sacral 2 segment and lower lumbar nerves form the pelvic plexus from which Pudendal nerves arise. The two are mixed nerves, they carry both sensory and motor stimulation.
Micturition reflex.
The center for the micturition is situated in the Pons of the brain.
Sensory information is carried from the bladder to the autonomic nerve center in the hypothalamus, which sends impulses to the pons for action. Somatic sensation is carried to the thalamus via the lateral spinothalamic tract, and then to the sensory cerebral cortex. Information for voluntary actions carried from the micturition center via the pudendal nerves to the bladder and external sphincter.
After voluntary micturition is started, the sensory input continues to flow to the center from the passage of urine through the urethra and the state of the bladder. Voluntary voiding is also helped by contraction of abdominal muscles. Voiding can be stopped and restarted by volition.
With these pieces of information at the back of the mind, it will be a lot easier to understand why a person develops urinary incontinence.
Urinary incontinence has several independent causes, at times more than one reason may be present.
1. Malalignment of the urethra with the bladder.
The urinary bladder rests on a muscular sling made by a group of pelvic muscles. The apex of the bladder continues as the urethra in the same straight line. The bladder is fairly mobile, allowing it to increase and decrease in size as urine is collected continuously and emptied periodically.
Repeated childbirth and loss of muscle mass in menopause, the muscular sling becomes flabby and the bladder sags downwards. Urethra's alignment is altered and results in voiding difficulties and retention of urine in the bladder. A similar situation arises in men with the hypertrophy of the prostate gland. Other conditions are pelvic tumors, fractures of the pelvic bones and hematoma. Sneezing, coughing, laughing and vigorous exercise, etc., produce leakage of urine from a full bladder.
2. Nerve damage.
Sensory nerve damage is often due to diabetes mellitus, both type 2 and type 1. Diabetes can also produce motor nerve damage. In the absence of sensation from an overfilled bladder, the pressure inside the bladder becomes higher than the resistance the internal sphincter can provide and the urine begins to leak. The damage to peripheral nerve in diabetes starts at the far end of the nerve fibers and progressively approaches the nerve cells. Toes and fingers show the damages first, but the process starts in all the systemic nerve fibers. The autonomic nervous system is generally spared unless the process is very aggressive and of longer duration. Other causes of peripheral neuropathy are - alcoholism, vitamin B1 and B12 deficiency, injury to nerve fibers in an accident or surgery, hypothyroidism. Several types of infections produce neuropathy - Lyme disease, HIV, shingles. Other causes of neuropathy generally spare the bladder.
3. Brain and spinal cord vascular events and injury.
The brain instructs the spinal centers for voluntary actions. It also sends inhibitory control over the lower motor neurons situated at the anterior horn cells of the spinal cord. In brain injury, like the middle cerebral artery stroke, that inhibitory control is lost and spasticity of muscles develops due to unopposed reflex contraction of muscles. The urinary bladder becomes small and urine drips continuously. Spinal cord injuries and transverse myelitis are additional conditions producing a similar incontinence. In a few CNS diseases, the urinary incontinence is invariably present, examples - Multiple sclerosis, Parkinson's disease, Alzheimer's disease, Chronic bilateral subdural hematoma and Low pressure hydrocephalus.
4. Muscle diseases.
In inherited muscle diseases, such as Charcot-Marie-Tooth disease, the urinary bladder loses muscles and fails to empty, and incontinence follows. Similarly, spinomuscular atrophy, the bladder loses muscle control and incontinence.
5. Prolonged bed rest and long term placement of urinary catheters.
The capacity of the urinary bladder is 500ml, however, if a lesser volume is used over some duration, the bladder adopts a lower volume. In prolonged use of an indwelling catheter, the sphincters become incontinent.
In prolonged bed rest, the pelvic muscles become flabby from non-use and the alignment of the urethra is altered and urinary retention and incontinence develop.
6. Repeated or chronic urinary bladder infection.
Infection derails normal control of bladder functions, develops an urge to urinate, frequency, a smaller capacity and incontinence.
Functional or emotional causes.
Psychosis and severe depression produce changes in perception of normal senses, and loss of voluntary actions in a timely fashion is lost.
Adverse effects of medication.
Hypnotics, sedatives and anti depression medications have adverse effects on the urinary center and on the bladder and urinary sphincters. In males, Anticholinergic drugs produce dysuria and retention of urine.
Pregnancy.
In normal pregnancy, as the gravid uterus enlarges and grows upwards, it raises the bladder neck with it, the bladder capacity also increases and some retention of urine is normal. In advanced pregnancy, wetting undergarments occurs often.
Incidence of urinary incontinence.
There are about 13 million cases of urinary incontinence in the USA alone. About half of them are nursing home residents. In general, female patients outnumber male patients. Most of the patients are elderly with various chronic illnesses, younger patients are those with developmental delays or have congenital neurological diseases. Spinal cord injury sustained in sports and auto accidents accounts for a handful.
Prevention and Treatment of Urinary Incontinence.
Training at the toilet starts in early childhood. It requires a great deal of patience and love in toilet training. It is important not to threaten or punish a child for an accidental bed-wetting. Fear and intimidation are very counterproductive.
In alcoholism, diabetes mellitus, prompt medical management and timely treatment with antibiotics of infections go a long way to avoid the development of urinary incontinence. Obstruction to the bladder neck by an enlarged prostate gland in males and pelvic tumors in both sexes should be addressed surgically. Prolonged indwelling catheter should be avoided, and various alternative methods to indwelling catheter are available and should be used. Retraining of voluntary voiding should be the goal in all cases where intact bladder innervation is preserved, and that should include CVA and spinal cord injury.
Surgical treatment:
In advanced pelvic malignancy, the bladder may have to be removed. A urinary conduit is created from a loop of the ilium. At times, transcutaneous stents are placed to drain the urine from both ureters. Various other forms of urinary diversion operations are used based on specific circumstances.
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