Kidney Stones in Adults
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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 certain
metabolic disorders such as hyperparathyroidism are
also linked to stone formation.
In addition, more than 70
percent of people with a rare hereditary disease
called renal tubular acidosis develop kidney stones.
Cystinuria and hyperoxaluria
are two other rare, inherited metabolic disorders
that often cause kidney stones. In cystinuria, too
much of the amino acid cystine, which does not
dissolve in urine, is voided. This can lead to the
formation of stones made of cystine. In patients
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.
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Shapes of various stones. Sizes are usually
smaller than shown here. |
Hypercalciuria is inherited.
It is the cause of stones in more than half of
patients. Calcium is absorbed from food in excess
and is lost 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 which is a disorder of uric acid
metabolism, gout, excess intake of vitamin D,
urinary tract infections, and blockage of the
urinary tract. Certain diuretics which are commonly
called 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. People who take the
protease inhibitor indinavir, a drug used to treat
HIV infection, are at risk of developing kidney
stones.
What are the
symptoms?
Kidney stones often do not
cause any symptoms. Usually, the first symptom of a
kidney stone is extreme pain, which occurs when a
stone acutely blocks the flow of urine. 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 in
the back and side in the area of the kidney or in
the lower abdomen. Sometimes nausea and vomiting
occur. Later, pain may spread to the groin.
If the stone is too large to
pass easily, 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 appear in the urine. As the stone moves
down the ureter closer to the bladder, you 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, you should contact a doctor
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. If they
are small, these stones would likely pass out of the
body 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 test called a CT
(computed tomography) scan or an IVP (intravenous
pyelogram). The results of all these tests help
determine the proper treatment.
How are kidney
stones treated?
Fortunately, surgery is not
usually necessary. 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.
Often, you can stay home during this process,
drinking fluids and taking pain medication as
needed. The doctor usually asks you to save the
passed stone(s) for testing. (You can catch it in a
cup or tea strainer used only for this purpose.)
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