Myths about Kidney Stones

by National Institute of Health

Kidney stones. Just mention them and people cringe - and for good reason. They are one of the most painful conditions a person can have. Chances are you know someone who's had them. More people are developing kidney stones, and researchers are trying to find out why and what can be done to prevent them.

But what exactly is a kidney stone? Kidney stones are hard masses developed from crystals that build up in the kidney, the organ that makes urine. These crystals can contain various combinations of chemicals, but are most often made of calcium in combination with either oxalate or phosphate. These chemicals are part of a normal diet and make up important parts of the body, such as bones and muscles. The crystals normally remain tiny enough to travel through the urinary tract and pass out of the body in the urine without being noticed. But in some people, the crystals stick together and continue to build up to form kidney stones.

Many people have misconceptions about kidney stones. Some think that stones occur only rarely and mainly in people who are already ill. But now we know that's changing. Get the facts about how research is offering new hope to those who suffer from this increasingly common condition.

Myth: Kidney stones are rare.

Fact: Kidney stones are one of the most common disorders of the urinary tract.

NIH's National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) estimates that up to ten percent of Americans will have a kidney stone at some point in their lives, and most will be between the ages of 20 and 40.

Over the past 20 years, the number of people with kidney stones has been increasing. Scientists don't have an explanation for this, but they think it may be related to diet and lifestyle. "Kidney stones are becoming a common occurrence in adults, and it looks like a combination of environmental and genetic factors may be responsible," says Dr. Thomas Hostetter, director of NIDDK's National Kidney Disease Education Program.

Myth: Only men get kidney stones.

Fact: Women get kidney stones too. Even children can get them.

Although men tend to develop kidney stones more frequently than women, the number of women with kidney stones has been increasing. Even children can have kidney stones, although less often than adults.

"Most children with kidney stones usually have a genetic or metabolic disease that makes them more likely to form stones," explains Dr. Hostetter.

If you have a family history of kidney stones, you are also more likely to develop them. Some people with a family history are believed to have a defective gene that results in excess calcium in their urine. NIDDK researchers are attempting to find out more about the genes responsible for this disorder, and to see if there are any other unusual factors that make these families more susceptible to kidney stones.

Myth: Eating certain foods will cause kidney stones to develop.

Fact: Not usually.

In general, scientists don't think that eating any specific foods causes stones to form in people who are not already susceptible. Dr. Hostetter says that, in some people, a diet high in protein may lead to kidney stones because extra protein causes calcium to be excreted from the body, raising calcium levels in the urine. For a person without any history of kidney stones, a diet with moderate amounts of protein should be followed, he advises.

People with urinary tract infections, kidney disorders such as cystic kidney diseases, and certain rare, inherited metabolic disorders are also more likely to develop kidney stones. In some of these susceptible people, the foods they eat can have an influence on the development of their kidney stones. For example, if you are at higher risk for kidney stones, your doctor may tell you to limit or avoid foods containing higher levels of oxalate, which include chocolate, coffee, beer, dairy products, and some fruits and vegetables.

Myth: Most kidney stones are formed from calcium, so calcium in the diet should be reduced.

Fact: That used to be what doctors thought, but no longer.

For years, doctors thought a low-calcium diet was the best way to prevent kidney stones, especially in those who already had stones. But recent research has reversed that thinking. Dr. Hostetter explains that several studies have shown that low-calcium diets are not effective, and may actually be harmful, since they tend to increase the likelihood of low-bone density and osteoporosis.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.