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Kidney Stones Fact Book
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Overview
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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An Introduction to the Urinary Tract
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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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What Is a Kidney Stone?
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Kidney stones in kidney, |
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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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Who Gets Kidney Stones?
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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What Causes Kidney Stones?
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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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What Are the Symptoms?
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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How Are Kidney Stones Diagnosed?
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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How Are Kidney Stones Treated?
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.
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Extracorporeal Shockwave
Lithotripsy | 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.
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Percutaneous
nephrolithotomy | 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.
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Uteroscopic stone
removal | 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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Is There Any Current Research on Kidney Stones?
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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Prevention Points to Remember
- 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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Foods and Drinks Containing Calcium and Oxalate
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.
Keeping on Top of Your Condition
Keeping in tune with your disease or condition not only makes treatment less intimidating but also increases its chance of success, and has been shown to lower a patients risk of complications. As well, as an informed patient, you are better able to discuss your condition and treatment options with your physician.
A new service available to patients provides a convenient means of staying informed, and ensures that the information is both reliable and accurate. If you wish to find out more about HealthNewsflash's innovative service, take the tour.
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Additional Reading
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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Other Resources
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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