A kidney stone is a solid piece of material that forms in the kidney from substances in the urine. It may be as small as a grain of sand or as large as a pearl. Most kidney stones pass out of the body without help from a doctor. But sometimes a stone will not go away. It may get stuck in the urinary tract, block the flow of urine and cause great pain.

The following may be signs of kidney stones that need a doctor's help:

• Extreme pain in your back or side that will not go away
• Blood in your urine
• Fever and chills
• Vomiting
• Urine that smells bad or looks cloudy
• A burning feeling when you urinate

Your doctor will diagnose a kidney stone with urine, blood, and imaging tests.

If you have a stone that won't pass on its own, you may need treatment. It can be done with shock waves; with a scope inserted through the tube that carries urine out of the body, called the urethra; or with surgery.

Kidney stones are hard, pebble-like pieces of material that form in one or both of your kidneys when high levels of certain minerals are in your urine. Kidney stones rarely cause permanent damage if treated by a health care professional.

Kidney stones vary in size and shape. They may be as small as a grain of sand or as large as a pea. Rarely, some kidney stones are as big as golf balls. Kidney stones may be smooth or jagged and are usually yellow or brown.

A small kidney stone may pass through your urinary tract on its own, causing little or no pain. A larger kidney stone may get stuck along the way. A kidney stone that gets stuck can block your flow of urine, causing severe pain or bleeding. Learn more about your urinary tract and how it works.

If you have symptoms of kidney stones, including severe pain or bleeding, seek care right away. A doctor, such as a urologist, can treat any pain and prevent further problems, such as a urinary tract infection (UTI).

Do kidney stones have another name?

The scientific name for a kidney stone is renal calculus or nephrolith. You may hear health care professionals call this condition nephrolithiasis, urolithiasis, or urinary stones.

Kidney stones are common and are on the rise. About 11 percent of men and 6 percent of women in the United States have kidney stones at least once during their lifetime.

You probably have one of four main types of kidney stones. Treatment for kidney stones usually depends on their size, location, and what they are made of.

Calcium stones

Calcium stones, including calcium oxalate stones and calcium phosphate stones, are the most common types of kidney stones. Calcium oxalate stones are more common than calcium phosphate stones.

Calcium from food does not increase your chance of having calcium oxalate stones. Normally, extra calcium that isn’t used by your bones and muscles goes to your kidneys and is flushed out with urine. When this doesn’t happen, the calcium stays in the kidneys and joins with other waste products to form a kidney stone.

Uric acid stones

A uric acid stone may form when your urine contains too much acid. Eating a lot of fish, shellfish, and meat—especially organ meat—may increase uric acid in urine.

Struvite stones

Struvite stones may form after you have a UTI. They can develop suddenly and become large quickly.

Cystine stones

Cystine stones result from a disorder called cystinuria that is passed down through families. Cystinuria causes the amino acid cystine to leak through your kidneys and into the urine.

Men are more likely to develop kidney stones than women. If you have a family history of kidney stones, you are more likely to develop them. You are also more likely to develop kidney stones again if you’ve had them once.

You may also be more likely to develop a kidney stone if you don’t drink enough liquids.

People with certain conditions

You are more likely to develop kidney stones if you have certain conditions, including

• a blockage of the urinary tract
• chronic, or long-lasting, inflammation of the bowel
• cystic kidney diseases, which are disorders that cause fluid-filled sacs to form on the kidneys
• cystinuria
• digestive problems or a history of gastrointestinal tract surgery
• gout, a disorder that causes painful swelling of the joints
• hypercalciuria, a condition that runs in families in which urine contains unusually large amounts of calcium; this is the most common condition found in people who form calcium stones
• hyperoxaluria, a condition in which urine contains unusually large amounts of oxalate
• hyperparathyroidism, a condition in which the parathyroid glands release too much parathyroid hormone, causing extra calcium in the blood
• hyperuricosuria, a disorder in which too much uric acid is in the urine
• obesity
• repeated, or recurrent, UTIs
• renal tubular acidosis, a disease that occurs when the kidneys fail to remove acids into the urine, which causes a person’s blood to remain too acidic

People who take certain medicines

You are more likely to develop kidney stones if you are taking one or more of the following medicines over a long period of time:

• diuretics, often called water pills, which help rid your body of water
• calcium-based antacids
• indinavir, a protease inhibitor used to treat HIV infection
• topiramate, an anti-seizure medication

Kidney stones are caused by high levels of calcium, oxalate, and phosphorus in the urine. These minerals are normally found in urine and do not cause problems at low levels.

Certain foods may increase the chances of having a kidney stone in people who are more likely to develop them.

Symptoms of kidney stones include

• sharp pains in your back, side, lower abdomen, or groin
• pink, red, or brown blood in your urine, also called hematuria
• a constant need to urinate
• pain while urinating
• inability to urinate or can only urinate a small amount
• cloudy or bad-smelling urine

See a health care professional right away if you have any of these symptoms. These symptoms may mean you have a kidney stone or a more serious condition.

Your pain may last for a short or long time or may come and go in waves. Along with pain, you may have

• nausea
• vomiting

Other symptoms include

• fever
• chills

Health care professionals use your medical history, a physical exam, and lab and imaging tests to diagnose kidney stones.

A health care professional will ask if you have a history of health conditions that make you more likely to develop kidney stones. The health care professional also may ask if you have a family history of kidney stones and about what you typically eat. During a physical exam, the health care professional usually examines your body. The health care professional will ask you about your symptoms.

Health care professionals may use lab or imaging tests to diagnose kidney stones.

Lab tests

Urine tests can show whether your urine contains high levels of minerals that form kidney stones. Urine and blood tests can also help a health care professional find out what type of kidney stones you have.

Urinalysis. Urinalysis involves a health care professional testing your urine sample. You will collect a urine sample at a doctor’s office or at a lab, and a health care professional will test the sample. Urinalysis can show whether your urine has blood in it and minerals that can form kidney stones. White blood cells and bacteria in the urine mean you may have a urinary tract infection.

Blood tests. A health care professional may take a blood sample from you and send the sample to a lab to test. The blood test can show if you have high levels of certain minerals in your blood that can lead to kidney stones.

Imaging tests

Health care professionals use imaging tests to find kidney stones. The tests may also show problems that caused a kidney stone to form, such as a blockage in the urinary tract or a birth defect. You do not need anesthesia for these imaging tests.

Abdominal x-ray. An abdominal x-ray is a picture of the abdomen that uses low levels of radiation NIH external link and is recorded on film or on a computer. An x-ray technician takes an abdominal x-ray at a hospital or outpatient center, and a radiologist reads the images. During an abdominal x-ray, you will lie on a table or stand up. The x-ray technician will position the x-ray machine over or in front of your abdomen and ask you to hold your breath so the picture won’t be blurry. The x-ray technician then may ask you to change position for additional pictures. Abdominal x-rays can show the location of kidney stones in the urinary tract. Not all stones are visible on abdominal x-ray.

Computed tomography (CT) scans. CT scans use a combination of x-rays and computer technology to create images of your urinary tract. Although a CT scan without contrast medium is most commonly used to view your urinary tract, a health care professional may give you an injection of contrast medium. Contrast medium is a dye or other substance that makes structures inside your body easier to see during imaging tests. You’ll lie on a table that slides into a tunnel-shaped device that takes the x-rays. CT scans can show the size and location of a kidney stone, if the stone is blocking the urinary tract, and conditions that may have caused the kidney stone to form.

You have come to the emergency department and the emergency doctor has recommended an imaging test to check for kidney stones. This summary will tell you about two types of imaging tests—a CT scan (computed tomography scan) and an ultrasound.

Kidney Stones and Possible Symptoms

The kidneys are bean-shaped organs that filter the waste chemicals out of your blood and make urine. A kidney stone is a hard piece of material that forms inside your kidney when tiny mineral crystals in your urine stick together.

Symptoms of kidney stones may include:

• Sharp pain in your back, side, lower belly (below your belly button), or groin that may come and go
• Nausea and vomiting
• Blood in your urine
• The feeling of sand or small particles passing through when you urinate
• Pain when you urinate
• Feeling like you need to urinate but cannot

Checking for Kidney Stones in the Emergency Department

First, the emergency doctor will give you medicine to help stop your pain. The medicine may be given by mouth. Or, it may be given through an intravenous (IV) needle placed in a vein in your arm. You may also be given medicine to help stop your nausea and vomiting. If you are dehydrated from vomiting, you may be given liquids through an IV tube.

Next, the emergency doctor will talk with you about your symptoms and medical history. If the emergency doctor thinks you might have a kidney stone, several tests may be done.

These may include:

• Urine Tests: To check for blood or mineral crystals in your urine or for signs of infection.
• Blood Tests: To check the health of your kidneys and for signs of a kidney or blood infection.
• Imaging Tests: To check for kidney stones in your urinary tract (kidneys, ureters, and bladder). Imaging tests may include a CT scan or an ultrasound.

Imaging Tests To Check for Kidney Stones

Two imaging tests to check for kidney stones are a CT scan and an ultrasound. If the first imaging test is not clear, you may need a second test.

In the past, a CT scan was often used as the first imaging test to check for kidney stones. But, because a CT scan exposes people to radiation, the emergency doctor may suggest an ultrasound instead as the first imaging test.

What Researchers Found

Both CT and ultrasound find most kidney stones.

Whether you have an ultrasound or a CT scan first:

• Does not affect the amount of pain you have or how quickly your pain will go away.
• Does not change the risk of having serious side effects or complications from kidney stones.
• Does not change the risk of having to go back to the emergency department or stay in the hospital.

Having an ultrasound first may help you avoid being exposed to radiation from a CT scan.

• If you have an ultrasound first, you may need a second imaging test, which may be a CT scan. But, most people who have an ultrasound first do not need a CT scan.

Note: If you and the emergency doctor decide on a CT scan, ask if it is possible to get a low-dose CT scan. Low-dose CT works as well as normal-dose CT to check for kidney stones and exposes you to less radiation.

Talking with the Emergency Doctor About Your Options for Imaging Tests

Talk with the emergency doctor about whether it might be better to have an ultrasound or a CT scan first to check for kidney stones.

You may want to think about:

• How you feel about being exposed to radiation with a CT scan.
• How you feel about possibly needing a second imaging test.

Next Steps If a Kidney Stone Is Found

If a kidney stone is small enough, it can move or "pass" through your urinary tract and out of your body on its own. If the stone cannot pass on its own, you may need treatment.

Large stones can get stuck in either a kidney or a ureter. A stone that becomes stuck may cause pain that does not go away and may damage the kidney if it is not treated.

If the emergency doctor thinks the kidney stone will pass on its own without any problems:

• You will probably be able to go home.
• You may be given medicines for pain and nausea to take home.
• You may be asked to drink water to help the kidney stone pass.
• You will be asked to watch for the kidney stone when you urinate. You may be told how to strain your urine to catch a stone that passes. If the stone does not pass, call your health care professional.

If the emergency doctor thinks the kidney stone will not pass on its own or may cause problems:

• You may need to stay in the hospital for treatment.
• You may need to see a specialist and may need surgery to remove the stone.

If your nausea and vomiting do not stop:

You may need to stay in the hospital.

Can Kidney Stones Come Back?

After the kidney stone has passed or after it is removed, another stone may form. People who have had a kidney stone in the past are more likely to get another stone in the future.

If you have had a kidney stone, talk with your health care professional about your risk of getting another one. Ask your health care professional what steps you can take to lower your risk of getting another kidney stone.

Complications of kidney stones are rare if you seek treatment from a health care professional before problems occur.

If kidney stones are not treated, they can cause

• hematuria, or blood in the urine
• severe pain
• UTIs, including kidney infections
• loss of kidney function

Health care professionals usually treat kidney stones based on their size, location, and what type they are.

Small kidney stones may pass through your urinary tract without treatment. If you’re able to pass a kidney stone, a health care professional may ask you to catch the kidney stone in a special container. A health care professional will send the kidney stone to a lab to find out what type it is. A health care professional may advise you to drink plenty of liquids if you are able to help move a kidney stone along. The health care professional also may prescribe pain medicine.

Larger kidney stones or kidney stones that block your urinary tract or cause great pain may need urgent treatment. If you are vomiting and dehydrated, you may need to go to the hospital and get fluids through an IV.

Kidney stone removal

A urologist can remove the kidney stone or break it into small pieces with the following treatments:

Shock wave lithotripsy. The doctor can use shock wave lithotripsy to blast the kidney stone into small pieces. The smaller pieces of the kidney stone then pass through your urinary tract. A doctor can give you anesthesia during this outpatient procedure.

Cystoscopy and ureteroscopy. During cystoscopy, the doctor uses a cystoscope to look inside the urethra and bladder to find a stone in your urethra or bladder. During ureteroscopy, the doctor uses a ureteroscope, which is longer and thinner than a cystoscope, to see detailed images of the lining of the ureters and kidneys. The doctor inserts the cystoscope or ureteroscope through the urethra to see the rest of the urinary tract. Once the stone is found, the doctor can remove it or break it into smaller pieces. The doctor performs these procedures in the hospital with anesthesia. You can typically go home the same day.

Percutaneous nephrolithotomy. The doctor uses a thin viewing tool, called a nephroscope, to locate and remove the kidney stone. The doctor inserts the tool directly into your kidney through a small cut made in your back. For larger kidney stones, the doctor also may use a laser to break the kidney stones into smaller pieces. The doctor performs percutaneous nephrolithotomy in a hospital with anesthesia. You may have to stay in the hospital for several days after the procedure.

After these procedures, sometimes the urologist may leave a thin flexible tube, called a ureteral stent, in your urinary tract to help urine flow or a stone to pass. Once the kidney stone is removed, your doctor sends the kidney stone or its pieces to a lab to find out what type it is.

The health care professional also may ask you to collect your urine for 24 hours after the kidney stone has passed or been removed. The health care professional can then measure how much urine you produce in a day, along with mineral levels in your urine. You are more likely to form stones if you don’t make enough urine each day or have a problem with high mineral levels.

To help prevent future kidney stones, you also need to know what caused your previous kidney stones. Once you know what type of kidney stone you had, a health care professional can help you make changes to your eating, diet, and nutrition to prevent future kidney stones.

Drinking liquids

In most cases, drinking enough liquids each day is the best way to help prevent most types of kidney stones. Drinking enough liquids keeps your urine diluted and helps flush away minerals that might form stones.

Though water is best, other liquids such as citrus drinks may also help prevent kidney stones. Some studies show that citrus drinks, such as lemonade and orange juice, protect against kidney stones because they contain citrate, which stops crystals from turning into stones.

Unless you have kidney failure, you should drink six to eight, 8-ounce glasses a day. If you previously had cystine stones, you may need to drink even more. Talk with a health care professional if you can’t drink the recommended amount due to other health problems, such as urinary incontinence, urinary frequency, or kidney failure.

The amount of liquid you need to drink depends on the weather and your activity level. If you live, work, or exercise in hot weather, you may need more liquid to replace the fluid you lose through sweat. A health care professional may ask you to collect your urine for 24 hours to determine the amount of urine you produce a day. If the amount of urine is too low, the health care professional may advise you to increase your liquid intake.

Medicines

If you have had a kidney stone, a health care professional also may prescribe medicines to prevent future kidney stones. Depending on the type of kidney stone you had and what type of medicine the health care professional prescribes, you may have to take the medicine for a few weeks, several months, or longer.

For example, if you had struvite stones, you may have to take an oral antibiotic for 1 to 6 weeks, or possibly longer.

If you had another type of stone, you may have to take a potassium citrate tablet 1 to 3 times daily. You may have to take potassium citrate for months or even longer until a health care professional says you are no longer at risk for kidney stones.

Talk with a health care professional about your health history prior to taking kidney stone medicines. Some kidney stone medicines have minor to serious side effects. Side effects are more likely to occur the longer you take the medicine and the higher the dose. Tell the health care professional about any side effects that occur when you take kidney stone medicine.

Hyperparathyroidism surgery

People with hyperparathyroidism, a condition that results in too much calcium in the blood, sometimes develop calcium stones. Treatment for hyperparathyroidism may include surgery to remove the abnormal parathyroid gland. Removing the parathyroid gland cures hyperparathyroidism and can prevent kidney stones. Surgery sometimes causes complications, including infection.

Drinking enough liquid, mainly water, is the most important thing you can do to prevent kidney stones. Unless you have kidney failure, many health care professionals recommend that you drink six to eight, 8-ounce glasses a day. Talk with a health care professional about how much liquid you should drink.

Studies have shown that the Dietary Approaches to Stop Hypertension (DASH) diet can reduce the risk of kidney stones.

Studies have shown that being overweight increases your risk of kidney stones. A dietitian can help you plan meals to help you lose weight.

Yes. If you have already had kidney stones, ask your health care professional which type of kidney stone you had. Based on the type of kidney stone you had, you may be able to prevent kidney stones by making changes in how much sodium, animal protein, calcium, or oxalate is in the food you eat.

You may need to change what you eat and drink for these types of kidney stones:

• Calcium Oxalate Stones
• Calcium Phosphate Stones
• Uric Acid Stones
• Cystine Stones

A dietitian who specializes in kidney stone prevention can help you plan meals to prevent kidney stones.

Calcium Oxalate Stones

Reduce oxalate

If you’ve had calcium oxalate stones, you may want to avoid these foods to help reduce the amount of oxalate in your urine:

• nuts and nut products
• peanuts—which are legumes, not nuts, and are high in oxalate
• rhubarb
• spinach
• wheat bran

Talk with a health care professional about other food sources of oxalate and how much oxalate should be in what you eat.

Reduce sodium

Your chance of developing kidney stones increases when you eat more sodium. Sodium is a part of salt. Sodium is in many canned, packaged, and fast foods. It is also in many condiments, seasonings, and meats.

Talk with a health care professional about how much sodium should be in what you eat. See tips to reduce your sodium intake.

Limit animal protein

Eating animal protein may increase your chances of developing kidney stones.

A health care professional may tell you to limit eating animal protein, including

• beef, chicken, and pork, especially organ meats
• eggs
• fish and shellfish
• milk, cheese, and other dairy products

Although you may need to limit how much animal protein you eat each day, you still need to make sure you get enough protein. Consider replacing some of the meat and animal protein you would typically eat with beans, dried peas, and lentils, which are plant-based foods that are high in protein and low in oxalate.

Talk with a health care professional about how much total protein you should eat and how much should come from animal or plant-based foods.

Get enough calcium from foods

Even though calcium sounds like it would be the cause of calcium stones, it’s not. In the right amounts, calcium can block other substances in the digestive tract that may cause stones. Talk with a health care professional about how much calcium you should eat to help prevent getting more calcium oxalate stones and to support strong bones. It may be best to get calcium from low-oxalate, plant-based foods such as calcium-fortified juices, cereals, breads, some kinds of vegetables, and some types of beans. Ask a dietitian or other health care professional which foods are the best sources of calcium for you.

Calcium Phosphate Stones

Reduce sodium

Your chance of developing kidney stones increases when you eat more sodium. Sodium is a part of salt. Sodium is in many canned, packaged, and fast foods. It is also in many condiments, seasonings, and meats.

Talk with a health care professional about how much sodium should be in what you eat. See tips to reduce your sodium intake.

Limit animal protein

Eating animal protein may increase your chances of developing kidney stones.

A health care professional may tell you to limit eating animal protein, including

• beef, chicken, and pork, especially organ meats
• eggs
• fish and shellfish
• milk, cheese, and other dairy products

Although you may need to limit how much animal protein you have each day, you still need to make sure you get enough protein. Consider replacing some of the meat and animal protein you would typically eat with some of these plant-based foods that are high in protein:

• legumes such as beans, dried peas, lentils, and peanuts
• soy foods, such as soy milk, soy nut butter, and tofu
• nuts and nut products, such as almonds and almond butter, cashews and cashew butter, walnuts, and pistachios
• sunflower seeds

Talk with a health care professional about how much total protein you should eat and how much should come from animal or plant-based foods.

Get enough calcium from foods

Even though calcium sounds like it would be the cause of calcium stones, it’s not. In the right amounts, calcium can block other substances in the digestive tract that may lead to stones. Talk with a health care professional about how much calcium you should eat to help prevent getting more calcium phosphate stones and to support strong bones. It may be best to get calcium from plant-based foods such as calcium-fortified juices, cereals, breads, some kinds of vegetables, and some types of beans. Ask a dietitian or other health care professional which foods are the best sources of calcium for you.

Uric Acid Stones

Limit animal protein

Eating animal protein may increase your chances of developing kidney stones.

A health care professional may tell you to limit eating animal protein, including

• beef, chicken, and pork, especially organ meats
• eggs
• fish and shellfish
• milk, cheese, and other dairy products

Although you may need to limit how much animal protein you have each day, you still need to make sure you get enough protein. Consider replacing some of the meat and animal protein you would typically eat with some of these plant-based foods that are high in protein:

• legumes such as beans, dried peas, lentils, and peanuts
• soy foods, such as soy milk, soy nut butter, and tofu
• nuts and nut products, such as almonds and almond butter, cashews and cashew butter, walnuts, and pistachios
• sunflower seeds

Talk with a health care professional about how much total protein you should eat and how much should come from animal or plant-based foods.

Losing weight if you are overweight is especially important for people who have had uric acid stones.

Cystine Stones

Drinking enough liquid, mainly water, is the most important lifestyle change you can make to prevent cystine stones. Talk with a health care professional about how much liquid you should drink.