When healthy, your kidneys cleanse the blood of waste products by producing urine. They also balance your sodium and potassium, and provide hormones necessary to regulate blood pressure and red blood cell production.
A kidney stone is a solid piece of material that develops from crystals that separate from urine and build up on the inner surfaces of the kidney. Normally, urine contains chemicals that prevent or inhibit the crystals from forming. However, in some people, stones still form. Crystals that remain small enough will travel through the urinary tract and pass out of the body in the urine without even being noticed. Larger stones, however, can get stuck in a ureter, the bladder or the urethra. This may block the flow of urine and cause great pain. Learn more about preventing kidney stones here.
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. They may be smooth, irregular in shape or jagged, and are usually yellow or brown in color.
Different types 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 with the rest of the urine. In some people, however, the calcium that stays behind joins with other waste products to form a stone.
- Struvite stones may form after an infection in the urinary system. They contain the mineral magnesium and the waste product ammonia.
- Uric acid stones may form when there is too much acid in the urine.
- Cystine stones are rare and are caused by a disease (cystinosis) that runs in families.
Who is affected by kidney stones
Kidney stones are one of the most painful disorders, and one of the most common disorders of the urinary tract. The National Institute of Diabetes and Kidney Disease (NIDKD) estimates that about a million people in the United States are treated for kidney stones each year. Those most affected include:
- Men, although the number of women who develop kidney stones has been increasing
- People between age 20 and 40
- Anyone who has previously developed a stone
- Those with a family history of stone formation
Conditions that may increase the chance for developing kidney stones include:
- 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 stones
- Overactive parathyroid glands
- Urinary tract infections
- Chronic dehydration
- Bowel disease
- High blood pressure
- Hyperuricosuria (a disorder of uric acid metabolism)
- Inflammatory bowel disease (Crohn's disease and ulcerative colitis)
- Intestinal bypass or ostomy surgery
Additionally, some diuretics or calcium-based antacids may increase the risk for kidney stones because they boost the amount of calcium in the urine.