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Also see:
What Are
Kidney Stones?
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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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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, |
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?
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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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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?
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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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How
Are Kidney Stones Diagnosed?
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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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How Are
Kidney Stones Treated?
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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.
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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?
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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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Prevention
Points to Remember
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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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Foods and
Drinks Containing Calcium and Oxalate
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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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Additional
Reading
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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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Other
Resources
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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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National Kidney and Urologic Diseases Information Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
E-mail: nkudic@info.niddk.nih.gov
The National Kidney and Urologic Diseases Information Clearinghouse
(NKUDIC) is a service of the National Institute of Diabetes and Digestive and Kidney
Diseases (NIDDK). The NIDDK is part of the National Institutes of Health under the U.S.
Public Health Service. Established in 1987, the clearinghouse provides information about
diseases of the kidneys and urologic system to people with kidney and urologic disorders
and to their families, health care professionals, and the public. NKUDIC answers
inquiries; develops, reviews, and distributes publications; and works closely with
professional and patient organizations and Government agencies to coordinate resources
about kidney and urologic diseases.
Publications produced by the clearinghouse are carefully reviewed
for scientific accuracy, content, and readability.
This e-text is not copyrighted. The clearinghouse encourages users
of this e-pub to duplicate and distribute as many copies as desired.
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NIH Publication No. 94-2495
April 1994 e-text posted: 12 February 1998 |
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