What is a kidney stone?
A kidney stone is a hard, pebble-like deposit that forms in one or both kidneys. It
may travel down through the urinary tract. The stones may be as small as a grain of
sand or as large as a pearl. Rarely, they can be as big as golf balls. A stone may
be smooth, irregular in shape, or jagged. Most are yellow or brown in color. There
are different types of kidney stones:
Calcium stones. Calcium stones are the most common type of stones. Calcium is a normal part of a healthy
diet and is used by bones and muscles. Calcium not used by the body goes to the kidneys
where it is normally flushed out with the urine. In some people, the calcium that
stays behind bonds with other waste products to form a stone.
Struvite stones. Struvite stones contain the mineral magnesium and the waste product ammonia. It may
form after an infection in the urinary tract.
Uric acid stones. Uric acid stones may form when there is too much acid in the urine. This type can
be seen in people who have gout.
Cystine stones. Cystine is one of the building blocks that make up muscles, nerves, and other parts
of the body. It can build up in the urine and form a stone. Cystine stones are rare
and often run in families.
Kidney stones are very painful. They are also one of the most common problems of the
What causes a kidney stone?
A kidney stone develops from crystals that build up in the kidney. Urine normally
contains chemicals that prevent or slow the crystals from forming. But stones still form
in some people. Small crystals can travel through the urinary tract and pass out of
the body in the urine without even being noticed. A larger stone can get stuck in
a ureter. The ureter is the small tube between the kidney and the bladder. A large
stone can also get stuck in the bladder or the urethra. The urethra is the tube from
the bladder that takes urine out of the body. A large stone may block the flow of
urine and cause great pain.
Who is at risk for kidney stones?
You are more likely to get a kidney stone if you:
Are white. Whites are at higher risk than African Americans.
Are male. Kidney stones happen more often in men, but the number of women who get
kidney stones has been growing.
Are age 20 to 40.
Have had a stone in the past. Once you’ve had 1 stone, you are more likely to get
These are factors you can control:
How much fluid you drink. If you don’t drink enough fluids and tend to be dehydrated,
you are at a higher risk for kidney stones.
Your diet. Eating a diet that is high in protein, sodium, and dark green vegetables
(oxalate-rich types of foods) can increase your risk for kidney stones.
Your weight. Being overweight increases insulin resistance in your body. Insulin resistance
increases the amount of calcium filtered into the urine. In turn, that increases the
risk of developing a kidney stone.
Medicines. Some medicines can increase your risk for kidney stones. Common medicines
include water pills (diuretics) and antiviral medicines.
These things you can't control:
Certain diseases that cause ongoing higher levels of calcium in the blood. More calcium
can cause dehydration because you make more urine. The extra calcium in the kidney
solidifies into a stone.
Surgery. Surgeries on the digestive tract including the intestines and gastric bypass
can make you more likely to have long-term (chronic) dehydration. Or you may develop
diseases that cause chronic diarrhea and dehydration. These increase the risk for
Family history. Inherited factors or a family history of kidney stones can raise your
Past urinary tract infections that kept returning
Low estrogen. Women with low estrogen levels after menopause or after removal of the
ovaries are at greater risk for kidney stones.
Gender. Men between the ages of 30 and 50 are the most likely to get kidney stones.
High uric acid level. Diseases that raise uric acid levels (gout) raise your risk
Diabetes. Insulin resistance from diabetes can cause an increase in the amount of
calcium filtered into the urine. That raises the risk for a kidney stone.
What are the symptoms of kidney stones?
These are the most common symptoms of kidney stones:
Extreme, sharp pain in the back, side, lower belly (abdomen), or groin that will not
go away. Changing positions doesn't help. Pain may last for a short or long time and
may come and go in waves.
Blood in the urine
Nausea and vomiting
Cloudy or odorous urine
Can't urinate or you urinate only a small amount
A burning feeling when you urinate
Fever and chills
The symptoms of kidney stones may look like other health problems. Call your healthcare
provider get medical care right away.
How are kidney stones diagnosed?
Your healthcare provider will ask about your health history and do a physical exam.
You may have other tests. These include:
Intravenous pyelogram (IVP). This test is a series of X-rays of the kidney, ureters, and bladder with the injection
of a contrast dye into the vein. It helps find tumors, kidney stones, or blockages.
It can also check blood flow to the kidney.
CT scan. This imaging test uses X-rays and a computer to make detailed images of the body.
A CT scan shows details of the bones, muscles, fat, and organs.
Urinalysis. This lab exam looks at urine for various cells and chemicals, such as red blood cells,
white blood cells, infection, or extra protein.
Blood tests. These are lab exams of the blood to look for substances that might cause a stone to
form. These tests can also assess how well your kidneys are working.
Renal ultrasound. This noninvasive test bounces sound waves off the kidney. It sends a picture of the
kidney to a video screen. This test is used to find the size and shape of the kidney.
It can also see a mass, kidney stone, cyst, or other blockage in the kidney.
How are kidney stones treated?
Treatment will depend on your symptoms, age, and general health. It will also depend
on how severe the condition is.
See your healthcare provider right away if you think you have a kidney stone. Some
kidney stones pass out of the body on their own without treatment. In cases that cause
lasting symptoms or other complications, kidney stones may be treated with one of
Shock waves or extracorporeal shock wave lithotripsy (ESWL). This treatment uses a machine to send shock waves directly to the kidney stone. It
breaks a large stone into smaller stones that will pass through the urinary tract.
There are 2 types of shock wave machines. In one, you sit in a tub of water. In the
other, you lie on a table.
Ureteroscope. A long wire with a camera attached to it is inserted into the urethra. The wire is
passed up through the bladder to the ureter where the stone is located. A tiny cage
is used to grab the stone and remove it.
Tunnel surgery (percutaneous nephrolithotomy). A small cut is made in your back and a narrow tunnel is made through the skin to the
stone inside the kidney. The surgeon can remove the stone through this tunnel.
Potassium citrate. Your healthcare provider may prescribe potassium citrate tablets to treat stones
made of calcium and uric acid that aren't causing a blockage. You take the tablets
with plenty of fluids. The citrate may help dissolve and drain the stone with the
Can kidney stones be prevented?
The best ways to prevent kidney stones are:
Drink more water to prevent dehydration. Up to 12 glasses of water a day, or as your
healthcare provider advises, can help to flush away the substances that form stones
in the kidneys. Ginger ale, lemon-lime sodas, and fruit juices are also OK. But water
Limit coffee, tea, and cola to 1 or 2 cups a day. The caffeine may cause a rapid loss
Talk with your healthcare provider or a dietitian about any diet changes.
Take medicines prescribed to prevent calcium and uric acid stones from forming.
When should I call my healthcare provider?
Call your healthcare provider or seek immediate medical attention if your symptoms
get worse or you have new symptoms.
Key points about kidney stones
A kidney stone is a piece of hard sediment that forms in the kidney. It develops when
certain substances that are filtered in the urine crystallize and stick together in
the kidney creating a stone.
Most stones are made of calcium, although stones can be formed from other substances.
Dehydration and certain medicines also increase the risk for kidney stones.
Kidney stones cause pain with urination as the stone passes through the urinary tract.
Some kidney stones can't be passed out of your body because they are too large and
become stuck in the urinary tract. This causes great pain. It may also block the flow
of urine. This needs medical care right away.
You may be able to prevent kidney stones by staying away from certain foods and drinking
plenty of water.
Once you have had a kidney stone, you are more likely to have another stone.
Tips to help you get the most from a visit to your healthcare provider:
Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your provider tells
At the visit, write down the name of a new diagnosis and any new medicines, treatments,
or tests. Also write down any new instructions your provider gives you.
Know why a new medicine or treatment is prescribed and how it will help you. Also
know what the side effects are.
Ask if your condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if you do not take the medicine or have the test or procedure.
If you have a follow-up appointment, write down the date, time, and purpose for that
Know how you can contact your provider if you have questions.