About Kidney Stones

What is a kidney stone?

A kidney stone is a solid piece of material that forms from crystallization of substances in the urine. The stone may remain in the kidney or break loose and travel down the urinary tract.

A small stone may pass through the body, but a larger stone can get stuck in a ureter, the bladder or the urethra. This may block the flow of urine and cause great pain.

A kidney stone may be as small as a grain of sand or as large as a pearl, and some are as big as golf balls.

Who is at risk for kidney stones?

Approximately 12 to 14 percent of people in the United States have a type of urinary stone. Conditions that may increase the chance of developing kidney stones include: 

  • A family history of kidney stones
  • An inherited condition that causes the body to absorb too much calcium
  • A low level of citrate in the urine, which may contribute to calcium-based stones
  • Overactive parathyroid glands
  • Urinary tract infections
  • Gout
  • Bowel disease
  • High blood pressure

Kidney Stone IllustrationWhat are the symptoms of kidney stones?

  • Extreme, sharp pain in the back or side that will not go away. Changing positions does not help. Pain can come and go.
  • Blood in the urine
  • Nausea and vomiting
  • Cloudy or odorous urine
  • Frequent urination
  • A burning feeling when urinating
  • Fever and chills

The symptoms of kidney stones may resemble other conditions or medical problems. Always consult your physician to determine the cause of any of these symptoms.

Kidney StonesTypes of kidney 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 in urine. In some people, however, the calcium that stays behind joins with other waste products to form a stone.

Struvite stones are a type of stone that contains the mineral magnesium and the waste product ammonia. It may form after an infection in the urinary system.
Uric acid stones may form when there is too much acid in the urine.

Cystine stones are made up of cystine, a building block for muscles, nerves and other parts of the body. Cystine can build up in the urine and form a stone. Cystine stones are rare and often run in families.

Treatment for kidney stones: The Kidney Stone Center »