Kidney stones risk factors: who gets them and why

Signs 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, or a burning feeling when you urinate (MedlinePlus). NIDDK says to seek care right away for severe pain or bleeding (NIDDK definition and facts).

What kidney stones are

Kidney stones are hard, pebble-like pieces of material that form in one or both kidneys when high levels of certain minerals are in the urine. They can be as small as a grain of sand or, rarely, as big as a golf ball. A small stone may pass on its own with little or no pain; a larger one may get stuck, block the flow of urine and cause severe pain or bleeding (NIDDK definition and facts).

About 11 percent of men and 6 percent of women in the United States have kidney stones at least once in their lifetime (NIDDK definition and facts). Kidney stones are not the same as chronic kidney disease; for that, see kidney disease risk factors.

The four main types

• Calcium stones (calcium oxalate and calcium phosphate) are the most common. Calcium oxalate stones are more common than calcium phosphate stones. Calcium from food does not raise the chance of calcium oxalate stones (NIDDK definition and facts).
• Uric acid stones may form when urine contains too much acid. Eating a lot of fish, shellfish and meat, especially organ meat, may raise uric acid in urine (NIDDK definition and facts).
• Struvite stones may form after a urinary tract infection (UTI). They can develop suddenly and grow large quickly (NIDDK definition and facts).
• Cystine stones come from cystinuria, a disorder passed down through families (NIDDK definition and facts).

Who is more likely to get kidney stones

• Men more than women (NIDDK definition and facts).
• A family history of kidney stones (NIDDK definition and facts).
• Having had a stone before. You are more likely to get another (NIDDK definition and facts).
• Not drinking enough liquids (NIDDK definition and facts).
• Obesity. Studies have shown that being overweight raises the risk (NIDDK diet). The BMI calculator shows where your weight falls.

Certain conditions raise the risk, including (NIDDK definition and facts):

• a blockage of the urinary tract, or repeated UTIs
• long-lasting inflammation of the bowel, digestive problems or past gastrointestinal surgery
• cystic kidney diseases and renal tubular acidosis
• gout (see gout risk factors)
• hypercalciuria (too much calcium in the urine, which runs in families and is the most common condition found in people who form calcium stones), hyperoxaluria (too much oxalate) and hyperuricosuria (too much uric acid)
• hyperparathyroidism, where the parathyroid glands cause extra calcium in the blood
• cystinuria

Certain medicines taken over a long time raise the risk: diuretics (water pills), calcium-based antacids, indinavir (an HIV medicine) and topiramate (an anti-seizure medicine) (NIDDK definition and facts). General safety advice: do not stop a prescribed medicine without talking to the doctor who prescribed it.

Diet and fluids

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 six to eight 8-ounce glasses a day; ask yours how much you should drink (NIDDK diet).

• Sodium. The chance of kidney stones rises when you eat more sodium, which is in many canned, packaged and fast foods (NIDDK diet).
• Animal protein. Eating animal protein may raise the chance of kidney stones (NIDDK diet).
• Oxalate. People who have had calcium oxalate stones may be advised to limit high-oxalate foods (NIDDK diet).
• Calcium from food. In the right amounts, calcium from food can block other substances that may cause stones, so cutting it is not the answer (NIDDK diet).
• DASH eating plan. Studies have shown that the DASH diet can lower the risk of kidney stones (NIDDK diet).

Which changes help depends on the type of stone you had, so ask your health care professional which type it was (NIDDK diet).

Symptoms

NIDDK lists these symptoms and says to see a health care professional right away if you have any of them (NIDDK symptoms and causes):

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

Nausea, vomiting, fever and chills can also occur (NIDDK symptoms and causes). Untreated stones can cause blood in the urine, severe pain, UTIs including kidney infections, and loss of kidney function (NIDDK definition and facts).

Blood in the urine has other causes too, including kidney cancer and bladder cancer.

Common questions

Does calcium cause kidney stones?

Calcium from food does not raise the chance of calcium oxalate stones, and in the right amounts it may help prevent them (NIDDK definition and facts) (NIDDK diet). Ask your health care professional how much calcium you need.

If I had one kidney stone, will I get another?

You are more likely to get kidney stones again once you have had one (NIDDK definition and facts). Knowing the stone type helps your doctor suggest changes (NIDDK diet).

How much water should I drink to prevent kidney stones?

Many health care professionals recommend six to eight 8-ounce glasses a day unless you have kidney failure. Talk with yours about the right amount for you (NIDDK diet).