Kidney Stones

Overview

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Kidney stones are hard, pebble-like pieces of material that form in one or both kidneys when high levels of certain minerals are present in urine. Healthcare professionals may also call this condition nephrolithiasis, urolithiasis, or urinary stones.

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. They may be smooth or jagged and are usually yellow or brown.

A small kidney stone may pass through the 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 the flow of urine, causing severe pain or bleeding. Kidney stones rarely cause permanent damage if treated by a healthcare professional.

Kidney stones are common. Many men and women have kidney stones at least once during their lifetime.

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.

There are four main types of kidney stones:

• Calcium stones: Calcium stones are the most common types. They include calcium oxalate stones and calcium phosphate stones. Calcium from food does not increase the chance of having calcium stones. However, foods high in oxalate, such as cashews and spinach, may increase risk of calcium oxalate stones. Normally, extra calcium that isn't used by our bones and muscles goes to the 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 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 having a urinary tract infection. 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 the kidneys and into the urine.

Kidney stones are not common in children, but the number of children affected has increased during the last several years. The higher rate may be due to changing eating habits, especially the rise in the amount of sodium children eat through processed foods and table salt. The rise in obesity and less active lifestyles may also cause more children to have kidney stones.

Children of all ages can develop kidney stones, including infants, but they occur more often in teens. A family history of kidney stones makes a child more likely to develop them. Children who've had kidney stones in the past have a greater chance of developing another kidney stone. 

Signs and Symptoms

Symptoms include:

• Sharp pains in your back, side, lower abdomen, or groin
• Pink, red, or brown blood in 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

The pain may last for a short or long time or may come and go in waves. Along with pain, symptoms may include: nausea, vomiting, fever, and chills.

If it’s a small stone that easily passes through the urinary tract, the person may not have symptoms at all.

Symptoms in children include the above, plus irritability, especially in young children. A child should see a healthcare professional right away when any of these symptoms occur, as they can be caused by a kidney stone or a more serious condition.

Related Health Effects

Complications of kidney stones are rare. But if not treated, kidney stones can cause:

• Hematuria, or blood in the urine
• Severe pain
• Urinary tract infections (UTIs), including kidney infections  
• Loss of kidney function

Causes and Risk Factors

Kidney stones are caused by high levels of calcium, oxalate (an organic compound found in plants), and phosphorus in the urine. These minerals and compounds 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.

Men are more likely than women to develop kidney stones. A family history of kidney stones also raises the risk of developing them. People who have had kidney stones once are also more likely to develop them again. Not drinking enough liquids also raises the risk.

Medical Conditions That Raise Risk

People with the following conditions are more likely to develop kidney stones.:

• A blockage of the urinary tract
• Chronic, or long-lasting, inflammation of the bowel
• Cystic kidney disease 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, 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

Medicines That Raise Risk

People taking one or more of the following medicines over a long period of time are more likely to develop kidney stones. These include:

• Diuretics, often called water pills, help rid the body of water
• Calcium-based antacids
• Indinavir, a protease inhibitor used to treat HIV infection
• Topiramate, an anti-seizure medicine

Prevention Guidance

In most cases, drinking enough liquids each day helps prevent most types of kidney stones. Drinking enough liquids keeps 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.

Diet and Nutrition

Studies have shown that a healthy diet can reduce the risk of kidney stones. Studies have also shown that being overweight increases the risk of kidney stones.  

People who previously had kidney stones may be able to prevent future kidney stones by making changes in how much sodium, animal protein, calcium, or oxalate is in their food.

For Calcium Oxalate Stones:

• Avoid cashews and almonds, rhubarb, spinach, and wheat bran to help reduce the amount of oxalate in the urine.
• Reduce sodium and be aware that sodium is found in many canned, packaged, and fast foods, as well as condiments, seasonings, and meats.
• A healthcare professional may advise limiting limiting animal protein, such as beef, chicken, pork (especially organ meats), eggs, fish, shellfish, milk, cheese, and other dairy products. Consider replacing some animal protein with beans, dried peas, and lentils, which are high in protein and low in oxalate.
• Get enough calcium from foods. In the right amounts, calcium can block other substances in the digestive tract that may cause stones. Get calcium from low-oxalate, plant-based foods such as calcium-fortified juices, cereals, breads, and certain types of vegetables and beans.

For calcium phosphate stones, reduce sodium and limit animal protein as described above. Get enough calcium from foods, including plant-based protein alternatives include legumes, soy foods, nuts and nut products, and sunflower seeds.

For uric acid stones, limit animal protein as described above. Losing weight if you are overweight is especially important for people who have had uric acid stones.

For cystine stones, drinking enough liquid, mainly water, is the most important lifestyle change to prevent cystine stones.

Medicines for Prevention

People who have had previous kidney stones may have to take medicine prescribed by a healthcare provider for a few weeks, several months, or longer. 

Discuss health history with a healthcare professional before taking kidney stone medicines, as some have minor to serious side effects.

Hyperparathyroidism Surgery

People with hyperparathyroidism have too much calcium in the blood and sometimes develop calcium stones. Treatment for hyperparathyroidism may include surgery to remove the abnormal parathyroid gland, which cures the condition and can prevent kidney stones.  

Diagnosis

Healthcare professionals use medical history, a physical exam, and lab and imaging tests to diagnose kidney stones. A healthcare professional will ask about health history that make some people more likely to develop kidney stones, such as a family history of kidney stones, and about what the person typically eats.

Lab Tests

Urine tests can show whether urine contains high levels of minerals that form kidney stones. Urine and blood tests also can help a healthcare professional determine the type of kidney stones.

Imaging Tests

Healthcare 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.  

• Abdominal X-ray: An abdominal X-ray is a picture of the abdomen that uses low levels of radiation and is recorded on film or on a computer. Abdominal X-rays can show the location of kidney stones in the urinary tract, though 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 pictures of the urinary tract. 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.
• Ultrasound: uses specialized sound waves to look at structures inside the body without exposing the child to radiation

Treatment and Management

Healthcare professionals usually treat kidney stones based on their size, location, and type.

Small kidney stones may pass through the urinary tract without treatment. If able to pass and save the kidney stone, a healthcare professional may send it to a lab to find out the type. Drink plenty of liquids to help move a kidney stone along. A healthcare professional may also prescribe pain medicine.

Larger kidney stones or kidney stones that block the urinary tract or cause great pain may need urgent treatment. If vomiting and dehydration occur, the patient may need to go to the hospital and get fluids through an intravenous (IV) line.

Removal Procedures

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

• Shock wave lithotripsy: The doctor uses shock waves to blast the kidney stone into small pieces, which then pass through the urinary tract. A doctor can give 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. During ureteroscopy, the doctor uses a longer and thinner instrument to see detailed pictures of the lining of the ureters and kidneys. Once the stone is found, the doctor can remove it or break it into smaller pieces. These procedures are performed in the hospital under anesthesia, and the patient typically can go home the same day.
• Percutaneous nephrolithotomy: The doctor uses a thin viewing tool called a nephroscope to locate and remove the kidney stone through a small cut made in the patient’s back. For larger kidney stones, the doctor may also use a laser to break the stones into smaller pieces. The patient may have to stay in the hospital for several days after this procedure.

After these procedures, the urologist may leave a thin flexible tube called a ureteral stent in the urinary tract to help urine flow or a stone pass. Once the kidney stone is removed, the doctor sends it to a lab to determine the type of stone.

The healthcare professional may also ask the patient to collect their urine for 24 hours after the kidney stone has passed or been removed to measure the amount of urine and mineral levels produced in a day.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on kidney stones.  

Find Treatment

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

Research

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

NIH supports research on the causes, prevention, diagnosis, and treatment of kidney related diseases and conditions. 

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.