Definition & Facts for Kidney Stones

What are kidney stones?

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).

Illustration of a human kidney with several kidney stones blocking the urinary tract.
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.

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 or urolithiasis.

What type of kidney stones do I have?

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.

How common are kidney 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.1

Who is more likely to develop kidney stones?

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:

What are the complications of kidney stones?

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

References

September 2016
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.