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Overview
of Kidney Stones 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.
An Introduction to
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.
What Is a Kidney
Stone? 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
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 etext 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.
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.
What Causes Kidney
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.
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.
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.
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. The First Step:
Prevention 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. Surgical Treatment Some type of surgery may
be needed to remove a kidney stone if the stone:
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.
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:
Researchers are also
working to develop new drugs with fewer side effects.
Prevention Points
to Remember
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.
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. Additional Reading Prevention and Treatment
of Kidney Stones. National Institutes of
Health Consensus Program Understanding
Kidney Stones...Management for a Lifetime. .
. Krames Communication, 110 Grundy Lane, San Bruno, CA 94066. (800) 333-3032.
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: Idnetifying 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.
Other Resources American Foundation for
Urologic Disease National Kidney
Foundation National Kidney and
Urologic Diseases Information Clearinghouse Oxalosis and
Hyperoxaluria Foundation For information about
hyperparathyroidism: National Institute of
Diabetes and Digestive and Kidney Diseases For information about
gout: National Arthritis and
Musculoskeletal and Skin Diseases
Hudson Valley
Lithotripsy Associates Hawthorne, NY
10532 |
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