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Kidney
Stones in Adults
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Overview
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Kidney
stones are one of the most painful disorders to afflict humans.
This ancient health problem has tormented people throughout
history. Scientists have even found evidence of kidney stones
in an Egyptian mummy estimated to be more than 7,000 years old.
Kidney
stones are one of the most common disorders of the urinary
tract. More than 1 million cases of kidney stones were diagnosed
in 1985. It is estimated that 10 percent of all people in
the United States will have a kidney stone at some point in
time. Men tend to be affected more frequently than women.
Most
kidney stones pass out of the body without any intervention
by a physician. Cases that cause lasting symptoms or other
complications may be treated by various techniques, most of
which do not involve major surgery. Research advances also
have led to a better understanding of the many factors that
promote stone formation.
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The
Urinary Tract
The
urinary tract, or system, consists of the kidneys, ureters,
bladder, and urethra. The kidneys are two bean-shaped organs
located below the ribs toward the middle of the back. The
kidneys remove extra water and wastes from the blood, converting
it to urine. They also keep a stable balance of salts and
other substances in the blood. The kidneys produce hormones
that help build strong bones and help form red blood cells.
Narrow
tubes called ureters carry urine from the kidneys to the bladder,
a triangle-shaped chamber in the lower abdomen. Like a balloon,
the bladder's elastic walls stretch and expand to store urine.
They flatten together when urine is emptied through the urethra
to outside the body.
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Kidney
stones in kidney, ureter and bladder
A
kidney stone develops from crystals that separate from urine
and build up on the inner surfaces of the kidney. Normally,
urine contains chemicals that prevent or inhibit the crystals
from forming. These inhibitors do not seem to work for everyone,
however, and some people form stones. If the crystals remain
tiny enough, they will travel through the urinary tract and
pass out of the body in the urine without even being noticed.
Kidney
stones may contain various combinations of chemicals. The
most common type of stone contains calcium in combination
with either oxalate or phosphate. These chemicals are part
of a person's normal diet and make up important parts of the
body, such as bones and muscles.
A
less common type of stone is caused by infection in the urinary
tract. This type of stone is called a struvite or infection
stone. Much less common are the uric acid stone and the rare
cystine stone.
Urolithiasis
is the medical term used to describe stones occurring in the
urinary tract. Other frequently used terms are urinary tract
stone disease and nephrolithiasis. Doctors also use terms
that describe the location of the stone in the urinary tract.
For example, a ureteral stone (or ureterolithiasis) is a kidney
stone found in the ureter. To keep things simple, the term
"kidney stones" is used throughout this e-text document.
Gallstones
and kidney stones are not related. They form in different
areas of the body. If a person has a gallstone, he or she
is not necessarily more likely to develop kidney stones.
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For
some unknown reason, the number of persons in the United States
with kidney stones has been increasing over the past 20 years.
White people are more prone to kidney stones than are black
people. Although stones occur more frequently in men, the number
of women who get kidney stones has been increasing over the
past 10 years, causing the ratio to change. Kidney stones strike
most people between the ages of 20 and 40. Once a person gets
more than one stone, he or she is more likely to develop others.
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Sizes
and Shapes of Various Stones
Doctors
do not always know what causes a stone to form. While certain
foods may promote stone formation in people who are susceptible,
scientists do not believe that eating any specific food causes
stones to form in people who are not susceptible.
A
person with a family history of kidney stones may be more
likely to develop stones. Urinary tract infections, kidney
disorders such as cystic kidney diseases, and metabolic disorders
such as hyperparathyroidism are also linked to stone formation.
In
addition, more than 70 percent of patients with adequate hereditary
disease called renal tubular acidosis develop kidney stones.
Cystinuria
and hyuperoxaluria are two other rare inherited metabolic
disorders that often cause kidney stones. In cystinuria, the
kidneys produce too much of the amino acid cystine. Cystine
does not dissolve in urine and can build up to form stones.
With hyperoxaluria, the body produces too much of the salt
oxalate. When there is more oxalate than can be dissolved
in the urine, the crystals settle out and form stones.
Absorptive
hypercalciuria occurs when the body absorbs too much calcium
from food and empties the extra calcium into the urine. This
high level of calcium in the urine causes crystals of calcium
oxalate or calcium phosphate to form in the kidneys or urinary
tract.
Other
causes of kidney stones are hyperuricosuria (a disorder of
uric acid metabolism), gout, excess intake of vitamin D, and
blockage of the urinary tact. Certain diuretics (water pills)
or calcium-based antacids may increase the risk of forming
kidney stones by increasing the amount of calcium in the urine.
Calcium
oxalate stones may also form in people who have a chronic
inflammation of the bowel or who have had an intestinal bypass
operation, or ostomy surgery. As mentioned above, struvite
stones can form in people who have had a urinary tract infection.
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Usually,
the first symptom of a kidney stone is extreme pain. The pain
often begins suddenly when a stone moves in the urinary tract,
causing irritation or blockage. Typically, a person feels a
sharp, cramping pain the back and side in the area of the kidney
or in the lower abdomen. Sometimes nausea and vomiting occur
with this pain. Later, the pain may spread to the groin.
If
the stone is too large to pass easily, the pain continues
as the muscles in the wall of the tiny ureter try to squeeze
the stone along into the bladder. As a stone grows or moves,
blood may be found in the urine. As the stone moves down the
ureter closer to the bladder, a person may feel the need to
urinate more often or feel a burning sensation during urination.
If
fever and chills accompany any of these symptoms, an infection
may be present. In this case, a doctor should be contacted
immediately.
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Sometimes
"silent" stones--those that do not cause symptoms--are
found on x-rays taken during a general health exam. These stones
would likely pass unnoticed.
More
often, kidney stones are found on an x-ray or sonogram taken
on someone who complains of blood in the urine or sudden pain.
These diagnostic images give the doctor valuable information
about the stone's size and location. Blood and urine tests
help detect any abnormal substance that might promote stone
formation.
The
doctor may decide to scan the urinary system using a special
x-ray test called an IVP (intravenous pyelogram). Together,
the results from these tests help determine the proper treatment.
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Fortunately,
most stones can be treated without surgery. Most kidney stones
can pass through the urinary system with plenty of water (2
to 3 quarts a day) to help move the stone along. In most cases,
a person can stay home during this process, taking pain medicine
as needed. The doctor usually asks the patient to save the passed
stone(s) for testing.
People
who have had more than one kidney stone are likely to form
another. Therefore, prevention is very important. To prevent
stones from forming, their cause must be determined. The urologist
will order laboratory tests, including urine and blood tests.
He or she will also ask about the patient's medical history,
occupation and dietary habits. If a stone has been removed,
or if the patient has passed a stone and saved it, the lab
can analyze the stone to determine its composition.
A
patient may be asked to collect his or her urine for 24 hours
after a stone has passed or been removed. The sample is used
to measure urine volume and levels of acidity, calcium, sodium,
uric acid, oxalate, citrate, and creatinine (a byproduct of
protein metabolism). The doctor will use this information
to determine the cause of the stone. A second 24-hour urine
collection may be needed to determine if the prescribed treatment
is working.
Lifestyle
Changes. A simple and most important lifestyle
change to prevent stones is to drink more liquids--water is
best. A recurrent stone former should try to drink enough
liquids throughout the day to produce at least 2 quarts of
urine in every 24-hour period.
Patients
with too much calcium or oxalate in the urine may need to
eat fewer foods containing calcium and oxalate.
Not
everyone will benefit from a low-calcium diet, however. Some
patients who have high levels of oxalate in their urine may
benefit from extra calcium in their diet. patients may be
told to avoid food with added vitamin D and certain types
of antacids that have a calcium base.
Patients
who have a very acid urine may need to eat less meat, fish,
and poultry. These foods increase the amount of acid in the
urine.
To
prevent cystine stones, patients should drink enough water
each day to reduce the amount of cystine that escapes into
the urine. This is difficult because more than a gallon of
water may be needed every 24 hours, a third of which must
be drunk during the night.
Medical
Therapy. The doctor may prescribe certain medications
to prevent calcium and uric acid stones. These drugs control
the amount of acid or alkali in the urine, key factors in
crystal formation. The drug allopurinol may also be useful
in some cases of hypercalciuria and hyperuricosuria.
Another
way a doctor may try to control hypercalciuria, and thus prevent
calcium stones, is by prescribing certain diuretics, such
as hydrochlorothiazide. These drugs decrease the amount of
calcium released by the kidneys into the urine.
Some
patients with absorptive hypercalciuria may be given the drug
sodium cellulose phosphate. This drug binds calcium in the
intestine and prevents it from leaking into the urine.
If
cystine stones cannot be controlled by drinking more fluids,
the doctor may prescribe the drug Thiola. This medication
helps reduce the amount of cystine in the urine.
For
struvite stones that have been totally removed, the first
line of prevention is to keep the urine free of bacteria that
can cause infection. The patient's urine will be tested on
a regular basis to be sure that bacteria are not present.
If
struvite stones cannot be removed the doctor may prescribe
a new drug called aetohydroamic acid (AHA). AHA is used along
with long-term antibiotic drugs to prevent the infection that
leads to stone growth.
To
prevent calcium stones that form in hyperparathyroid patients,
a surgeon may remove all of the parathyroid glands (located
in the neck). This is usually the treatment for hyperparathyroidism
as well. In most cases, only one of the glands is enlarged.
Removing the gland ends the patient's problem with kidney
stones.
Some
type of surgery may be needed to remove a kidney stone if
the stone:
- does
not pass after a reasonable period of time and causes constant
pain,
- is
too large to pass on its own,
- blocks
the urine flow,
- causes
ongoing urinary tract infection,
- damages
the kidney tissue or causes constant bleeding, or
- has
grown larger (as seen on follow up x-ray studies).
Until
recently, surgery to remove a stone was very painful and required
a lengthy recovery time (4 to 6 weeks). Today, treatment for
these stones is greatly improved. Many options exist that
do not require major surgery.
Extracorporeal
Shockwave Lithotripsy
Extracorporeal
shockwave lithotripsy (ESWL) is the most frequently used surgical
procedure for the treatment of kidney stones. ESWL uses shockwaves
that are created outside of the body to travel through the
skin and body tissues until the waves hit the dense stones.
The stones become sand-like and are easily passed through
the urinary tract in the urine.
There
are several types of ESWL devices. One device positions the
patient in the water bath while the shock waves are transmitted.
Other devices have a soft cushion or membrane on which the
patient lies. Most devices use either x-rays or ultrasound
to help the surgeon pinpoint the stone during treatment. For
most types of ESWL procedures, some type of anesthesia is
needed.
In
some cases, ESWL may be done on an outpatient basis. Recovery
time is short, and most people can resume normal activities
in a few days.
Complications
may occur with ESWL. Most patients have blood in the urine
for a few days after treatment. Bruising and minor discomfort
on the back or abdomen due to the shockwaves are also common.
To reduce the chances of complications, doctors usually tell
patients to avoid taking aspirin and other drugs that affect
blood clotting for several weeks before treatment.
In
addition, the shattered stone fragments may cause discomfort
as they pass through the urinary tract in the urine. In some
cases, the doctor will insert a small tube called a stent
through the bladder into the ureter to help the fragments
pass. Sometimes the stone is not completely shattered with
one treatment and additional treatments may be required.
Percutaneous
Nephrolithotomy
Sometimes
a procedure called percutaneous nephrolithotomy is recommended
to remove a stone. This treatment is often used when the stone
is quite large or in a location that does not allow effective
use of EWSL.
In
this procedure, the surgeon makes a tiny incision in the back
and creates a tunnel directly into the kidney. Using an instrument
called a nephroscope, the stone is located and removed. For
large stones, some type of energy probe (ultrasonic or electrohydraulic)
may be needed to break the stone into small pieces. Generally,
patients stay in the hospital for several days and may have
a small tube called a nephrostomy tube left in the kidney
during the healing process.
One
advantage of percutaneous nephrokithotomy over ESWL is that
the surgeon removes the stone fragments instead of relying
on their natural passage from the kidney.
Ureteroscopic
Stone Removal
Although
some ureteral stones can be treated with ESWL, urethroscopy
may be needed for mid- and lower-ureter stones. No incision
is made in this procedure. Instead, the surgeon passes a small
fiberoptic instrument called a ureteroscope through the urethra
and bladder into the ureter. The surgeon then locates the
stone and either removes it with a cage-like device or shatters
it with a special instrument that produces a form of shockwave.
A small tube or stent may be left in the ureter for a few
days after treatment to help the lining of the ureter heal.
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The
Division of Kidney, Urologic, and Hematologic Diseases of the
National Institutes of Diabetes and Digestive and Kidney Diseases
(NIDDK) funds research on the causes, treatments, and prevention
of kidney stones. The NIDDK is part of the Federal Government's
National Institutes of Health in Bethesda, Maryland.
New
drugs and the growing field of lithotripsy have greatly improved
the treatment of kidney stones. Still, NIDDK researchers and
grantees seek to answer questions such as:
- Why
do some people continue to have painful stones?
- How
can doctors predict, or screen, who is as risk for getting
stones?
- What
are the long-term effects of lithotripsy?
- Do
genes play a role in stone formation?
- What
is the natural substance(s) found in urine that blocks stone
formation?
Researchers
are also working to develop new drugs with fewer side effects.
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- People
who have a family history of stones or who have had more
than one stone are likely to develop another.
- A
good first step to prevent any type of stone is to drink
plenty of liquids--water is best.
- If
a person is at risk for developing stones, the doctor may
perform certain blood and urine tests. These tests will
determine which factors can be best altered to reduce that
risk.
- Some
patients will need medicines to prevent stones from forming.
- People
with chronic urinary tract infections and stones will often
need the stone removed if the doctor determines that the
infection results from the stone's presence. Patients must
receive careful followup to be sure that the infection has
cleared.
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Persons
prone to forming calcium oxalate stones may be asked by their
doctor to cut back on certain foods on this list.
- apples
- asparagus
- beer
- beets
- berries,
various (e.g., cranberries, strawberries)
- black
pepper
- broccoli
- cheese
- chocolate
- cocoa
- coffee
- cola
drinks
- collards
- figs
- grapes
- ice
cream
- milk
- oranges
- parsley
- peanut
butter
- pineapples
- spinach
- Swiss
chard
- rhubarb
- tea
- turnips
- vitamin
C
- yogurt
Persons
should not give up or avoid eating these types of foods without
talking to their doctor first. In most cases, these foods
can be eaten in limited amounts.
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Understanding
Kidney Stones . . . Management for a Lifetime, Krames Communication,
110 Grundy Lane, San Bruno, CA 94066. (800) 333-3032.
Coe,
F.L., et al., The Pathogenesis and Treatment of Kidney Stones,
New England Journal of Medicine, Vol. 327, No. 16,
pp.1141-1152, 1992.
Curhan,
G.C.,etal., A Prospective Study of Dietary Calcium and Other
Nutrients and the Risk of Symptomatic Kidney Stones, New
England Journal of Medicine, Vol. 328, No. 12, pp. 833-838,
1993.
Jenkins,
A.D., Upgrading Extracorporeal Shock Wave Lithotripsy, Contemporary
Urology, October 1991, pp. 11-12.
Lawson,
R.K., Smaller Means Safer Intraureternal Eletrohydraulic Lithotripsy,
Comtemporary Urology, October 1991, pp.51-58.
Lingeman,J.E.,
et al., Kidney Stones: Acute Management, Patient Care,
August 15, 1990, pp.20-42.
Lingeman,
J.E., et al., Kidney Stones: Identifying the Causes, Patient
Care, September 30, 1990, pp.31-46.
O'Brien,
W.M., Rotolo, J.E., Pahira, J.J., New Approaches in the Treatment
of Renal Calculi, American Family Physician, November
1987, pp. 181-94.
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American
Foundation for Urologic Disease
300 West Pratt Street
Baltimore, MD 21201-2463
(800) 242-2383; (410) 727-2908
National
Kidney Foundation
30 East 33rd Street
New York, NY 10016
(800) 622-9010; (212) 889-2210
National
Kidney and Urologic Diseases Information Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
Oxalosis
and Hyperoxaluria Foundation
12 Pleasant Street
Maynard, MA 01754
(888) 712-2432 PIN# 5392; (508) 461-0614
For
information about hyperparathyroidism:
National Institute of Diabetes and Digestive and Kidney Diseases
Building 31, Room 9A04
9000 Rockville Pike
Bethesda, MD 20892
(301) 496-3583
For
information about gout:
National Arthritis and Musculoskeletal and Skin Diseases
Information Clearinghouse
Box AMS
9000 Rockville Pike
Bethesda, MD 20892
(301) 495-4484
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Reference:
from the National Kidney and Urologic Diseases Information
Clearinghouse & the National Institute of Diabetes and
Digestive and Kidney Diseases
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