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Kidney
disease is a major health problem in this country, afflicting some
eight million Americans. Kidney and urinary tract diseases together
affect an estimated 20 million people, causing more than 95,000
deaths a year and contributing to an additional quarter of a
million.
Kidney disorders run the gamut from minor
infections to total kidney failure. Kidney disease can cause high
blood pressure, anemia, and elevated cholesterol. When chronic, it
can lead to depression and sexual dysfunction. Kidney stones,
diagnosed in more than one million Americans annually, can be
extremely painful and are a significant cause of hospital stays and
lost work days. But the picture is not entirely bleak.
Thanks to major medical advances, diagnosis and treatment
of kidney problems have improved significantly in the past 30 years. Even people
with complete kidney failure can now lead reasonably normal lives because of
modern dialysis techniques and new successes in transplantation. Today dialysis
keeps alive more than 220,000 Americans who would otherwise perish because of
kidney failure. Kidney transplants, first performed in the U.S. some 30 years
ago, have saved the lives of thousands more.
Why Are Your Kidneys So Vital?
Called the "master chemists" of the body, the
kidneys keep a variety of elements in balance. When the kidneys
become damaged, other organs suffer as well.
It's commonly known that the kidneys remove
waste products and excess fluids from the body via the urine, and
that they maintain a critical balance of salt, potassium and acid.
But most people are unaware that kidneys perform other vital
functions as well. For example, the kidneys produce a hormone --
erythropoietin or EPO -- that stimulates the production of red blood
cells. Other kidney hormones help regulate blood pressure and calcium
metabolism. The kidneys even synthesize the hormones that control
tissue growth.
Anytime the kidneys' ability to remove and
regulate water and chemicals is impaired by disease or blockage,
fluids and waste products accumulate, ultimately resulting in extreme
swelling and symptoms of uremia (an overload of toxic byproducts) or
kidney failure. The kidneys' various functions can each be affected
separately, so urine output may be normal despite significant kidney
disease.
Kidney diseases, which usually involve both
kidneys, are categorized as hereditary, congenital or
acquired.
Inherited kidney disorders usually begin
producing symptoms during the teen to adult years, and are often
serious.
Congenital kidney diseases typically
involve a malformation of the genitourinary tract that can lead to
blockages, which, in turn, can cause infection and/or destruction of
kidney tissue. Tissue destruction may then lead to chronic kidney
failure.
Acquired kidney disorders have numerous
causes, including blockages, drugs, and toxins. However, diabetes and
high blood pressure are by far the most common culprits.
How Your Amazing Kidneys Work
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The two fist-sized kidneys sit on
either side of the spine at the lower end of the rib cage.
Each consists of approximately one million nephrons; each
nephron contains a filtering apparatus called a glomerulus,
which is laced with tiny blood vessels; each glomerulus is
attached to a tubule. After blood is filtered in the
glomerulus, the remaining fluid passes along the tubule,
where chemicals and water are either added or extracted
according to the body's needs. The final product of this
process is the urine we eliminate.
The kidneys filter and return to the
bloodstream about 200 quarts of fluid every 24 hours.
Approximately two quarts are eliminated as urine, which
flows from the kidneys through the ureter to the bladder,
where it is stored for up to eight hours.
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Inherited Kidney Diseases
The most common inherited disorder is
polycystic kidney disease; others include Alport's syndrome,
hereditary nephritis, primary hyperoxaluria, and
cystinuria.
Polycystic kidney disease (or PKD) is
marked by the formation of fluid-filled cysts in the kidney tubules.
These cysts compress functioning kidney tissue, eventually replacing
it. In the most common type of the disease (autosomal dominant PKD),
almost half of the patients develop chronic kidney failure between
the ages of 40 and 60. The rarer form (autosomal recessive PKD)
causes kidney failure in early childhood.
In PKD, both kidneys become enlarged. Patients
experience back pain, blood in the urine, kidney stones, recurring
bladder or kidney infections, and high blood pressure.
Though there is no cure, careful management of
high blood pressure and prompt antibiotic treatment of kidney or
bladder infections can prolong life. Exercise to help maintain good
physical condition is frequently recommended as part of the treatment
program. Since PKD is progressive and often leads to kidney failure,
patients are counseled, given emotional support, and prepared for the
eventuality of dialysis or transplantation.
Congenital Kidney Diseases
There are two types of congenital kidney
disease. In one, malformations present at birth usually lead to some
type of blockage. This disrupts the normal flow of urine, causing it
to back up and exert increasing pressure on the kidneys, ultimately
leading to permanent damage. In the other form, the muscles of the
bladder fail to contract as they should, due to some abnormality in
the muscles or their nerve supply.
Though kidney malformations are common,
affecting up to 15 percent of the population, they generally don't
cause problems. Blockages that can lead to serious kidney
difficulties include the narrowing of the upper urinary tract
(ureteropelvic junction obstruction or ureteral
stenosis), congenital contracture of the bladder outlet
(vesical neck contracture), or narrowing of the channel from
the bladder to the outside of the body (urethral
stricture).
Urinary tract blockages require early
diagnosis, ordinarily accomplished by injecting dye into the
bloodstream or the bladder so that an X-ray can be taken. Specific
diagnostic procedures include intravenous urography and retrograde
pyelography. (The latter procedure sometimes actually relieves the
blockage, eliminating the need for surgery.) Non-invasive diagnostic
techniques include renal scans, ultrasound, and CT scans. Some
urinary tract blockages can be treated by abdominal surgery; others
can be relieved by surgery through the urethra.
Acquired Kidney Diseases
Inflammation of the kidneys, or nephritis, is
the primary characteristic of acquired kidney diseases. In the most
common of these, glomerulonephritis (also known as Bright's disease),
the glomerulus or filtering part of the kidney becomes inflamed. The
disease can be brief and severe, mild and protracted, or rapidly
progressive.
Acute post-streptococcal
glomerulonephritis typically starts about 10 days after the onset
of a strep throat or a skin infection such as impetigo. Though more
common in children, it can occur at any age. Most people recover
fully, but the few who don't may develop chronic kidney failure
within months.
Symptoms include a fall in urine output,
"smoke"- or "rust"-colored urine, and a burning sensation when
urinating. Swelling of the face, eyelids, and hands due to fluid
retention is also common, as are shortness of breath, a cough, and
high blood pressure.
Acute post-streptococcal glomerulonephritis usually heals
completely within three to 12 months after onset. The only treatment is the
relief of symptoms and complications. Accompanying high blood pressure must
be treated with an antihypertensive. Fluid retention is controlled with diuretics
(water pills), including metolazone (Mykrox, Zaroxolyn) or furosemide (Lasix).
Chronic glomerulonephritis is a term
used for a wide variety of diseases that cause progressive scarring
of the kidneys over a long period of time, often without any initial
symptoms. Frequently, the only findings in the early stages of the
illness are an abnormal urinalysis and high blood pressure. Edema
(fluid retention) and persistent high blood pressure appear as the
disease progresses. As with the acute form, the accompanying high
blood pressure must be treated with medication. A diet restricting
protein, sodium, and potassium is also often part of the treatment
plan. Steroids and other drugs have been used to treat this disease;
their success depends on the underlying cause.
Rapidly progressive glomerulonephritis
(RPGN) is characterized by a decrease in urine output and
progressive decline in kidney function over a three to six month
period or less. RPGN has no known cause, appears suddenly, and can
quickly lead to kidney failure. RPGN is irreversible once kidney
function is severely affected, but the kidneys may recover
significantly if treatment is begun early enough.
Nephrotic Syndrome: Though not a disease
in itself, this condition is often the result of other kidney
disorders or more generalized diseases (such as diabetes mellitus and
lupus erythematosus). It is marked by heavy loss of protein in the
urine, a low protein level in the blood, an increase in blood
cholesterol level, and edema (fluid retention). Prognosis is variable
and depends on the underlying cause; in some cases, the condition may
progress to end-stage kidney failure.
Some forms of nephrotic syndrome respond to
corticosteroids, which significantly reduce the amount of protein
lost in the urine. In those cases in which steroids do not help,
treatment consists of diuretics to control high blood pressure and
swelling due to fluid retention.
Acquired Kidney Obstructions: These are
generally mechanical in nature. Common causes include an enlarged
prostate gland in older men, sagging pelvic muscles in older women,
and tumors in the genitourinary organs of both males and females.
Kidney stones and scar tissue that develops as a result of
infections, x-ray treatment, and surgery may also cause blockage of
the urinary tract. Some of these obstructions can be alleviated by
surgery and follow-up medical treatment. Tumors are treated with
surgery, radiation, and appropriate medications.
Kidney Stones: These hard masses appear
when certain chemicals in the urine form crystals that stick
together. The crystals can grow into a stone as small as a grain of
sand or as large as a golf ball. Small stones are passed out of the
body with the urine. The larger ones can block urine flow or irritate
the lining of the urinary tract. Some individuals with kidney stones
have no symptoms, but most usually experience some of the following:
severe pain, nausea, and vomiting; burning and a frequent urge to
urinate; fever, chills, and weakness; cloudy or foul-smelling urine;
blood in the urine; and a blocked flow of urine. Serious infections
can result from a blockage.
Specialized x-rays or sound waves (ultrasound)
can be used to diagnose and identify the location and size of kidney
stones. Since 90 percent of stones are small enough to pass
naturally, treatment usually consists of methods to promote this,
such as drinking a lot of liquid. Medications that may be prescribed
include antibiotics (if an infection develops) and analgesics such as
meperidine (Demerol) for pain. Larger stones are often treated by
passing a telescopic device into the ureter or bladder and either
removing the stones or breaking them into small fragments with lasers
or sound waves. Alternatively, larger stones may be broken down by
high-energy shock waves. Only rarely is surgery necessary.
Drinking large amounts of fluids, taking
certain medications, and changing the diet may help prevent the
formation of new stones.
Treatment of Kidney Failure
As much as 90 to 95 percent of kidney function
can be lost before kidney failure becomes apparent. Symptoms include
loss of appetite, nausea and vomiting, extreme fatigue, difficulty
sleeping, itching and dry skin, muscle cramps, and twitching. Left
untreated, the buildup of waste products in the body can lead to
coma, seizure, and death.
Many years ago, kidney failure was inevitably
fatal. But modern medicine now offers three life-saving
treatments.
In hemodialysis an artificial kidney
machine carries out the vital functions the kidneys can no longer
perform. In this procedure, a person is connected to the machine by
plastic tubing that attaches to special blood vessels in the arm or
leg. The treatment can be done at home or at a dialysis
unit.
In peritoneal dialysis, waste products
from the blood are flushed from the body with fluid instilled and
drained through a catheter that has been surgically placed in the
abdomen. Once the catheter is in place, this technique is usually
done at home.
Since patients with kidney failure are often
anemic, many have to take a substance known as EPO (erythropoietin),
the synthetic form of a hormone that helps make red blood cells. Iron
supplements are also sometimes required.
Kidney transplantation, the third option
for people with kidney failure, has shown increasing success in
recent years. Depending on the quality of the match between donor and
recipient, there is an 80 to 90 percent chance that a transplanted
organ will still be functioning one year after the operation. The
major complication of a transplant, rejection of the organ, is
treated with such medications as steroids, azathioprine, and
cyclosporine. Many transplant patients also need blood pressure
medication, as well as drugs to prevent ulcers and infections.
Source: From the PDR® Family Guide to Prescription Drugs™
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