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Preventing kidney stones

Created: ; Last Update: May 18, 2017; Next update: 2020.

People who have had a kidney stone are quite likely to get another one. To prevent that from happening, it's usually enough to drink plenty of water and change your diet. Some people will still end up having kidney stones again and again. Medication is then an option.

About 30 to 50 out of 100 people who have had a kidney stone can expect to have another within five years. About 10 out of 100 will regularly develop kidney stones. Many people who are affected want to know what they can do to prevent new kidney stones from forming.

Because kidney stones can have so many different possible causes, the first thing to find out is the chemical composition of the stones. The levels of some substances in your blood and urine may also suggest a particular cause. About 80% of all kidney stones are made of calcium oxalate or calcium phosphate. Uric acid stones make up about 5 to 10% of all kidney stones. The rest are made of struvite, cystine or other less common substances.

Drinking enough fluids and possibly making changes to your diet is usually all you need to do to lower your risk of kidney stones. Medicine for preventing kidney stones may also be a good option for people who have a higher risk.

Does drinking a lot of fluids help?

Kidney stones develop if the urine is no longer able to hold dissolved calcium or uric acid salts because their concentrations are too high. These salts build up and form crystals, which can then develop into stones. The more diluted your urine is, the less likely it is that kidney stones will develop.

One study suggests that you can lower your risk of kidney stones by drinking more fluids. Participants drank enough to produce about 2.5 liters of urine per day. After a period of five years the study showed the following:

  • 27 out of 100 people who drank the same amount as they did before developed another kidney stone.
  • 12 out of 100 people who drank more than they did before developed another kidney stone.

The study participants found it easy to drink more fluids.

Try to avoid soft drinks

Many soft drinks like cola contain phosphoric acid (food additive E338), which may possibly increase the likelihood of kidney stones forming. So researchers have also tested whether cutting out soft drinks can lower your risk of kidney stones. Only one good-quality study has been done on this topic: Over 500 men who had previously all drunk at least 160 milliliters of soft drinks per day were advised to drink less. On average they lowered their consumption to less than 100 milliliters of soft drinks per day. Their risk of kidney stones dropped in comparison to the group who were not advised to drink less. The study showed the following after three years:

  • 41 out of 100 men who continued to drink the same amount of soft drinks had another kidney stone.
  • 34 out of 100 men who reduced their drink consumption had another kidney stone.

Some men dropped out of the study early, possibly because they found it difficult to adjust their drinking habits.

Is changing my diet a good idea?

Low-calcium diets are more likely to be harmful

Calcium stones are mostly made up of calcium oxalate. Both calcium and oxalate are found in many foods, but it's the amount that matters: Studies show that low-calcium food is more likely to increase the risk of kidney stones because more oxalate can enter the bloodstream when there isn't enough calcium in the food. So there is no reason for people who have had a calcium stone to start a low-calcium diet.

It's different when calcium is used as a dietary supplement. Studies show that this increases the risk of kidney stones - at least for women in menopause.

Major change in diet could help

The highest-quality study to date on diet and kidney stones involved men who had high levels of calcium in their blood. They were advised to do the following as part of comprehensive changes to their diet:

  • Drink plenty of fluids
  • Avoid oxalate-rich foods (especially walnuts, spinach, rhubarb, parsley and chocolate)
  • Make sure they get enough calcium (about 1,000 to 1,200 milligrams a day)
  • Eat less animal protein
  • Eat a diet low in salt

The men in the comparison group were only instructed to drink more fluids and to follow a diet low in oxalate and calcium.

The results show that a major change in diet can lower your risk of kidney stones:

  • If they didn't make major changes to their diet, 38 out of 100 men had another kidney stone within five years.
  • If they did make major changes to their diet, 20 out of 100 men had another kidney stone within five years.

Sometimes a fiber-rich diet is also recommended, but there's no scientific evidence that this kind of diet can prevent kidney stones.

The impact of a low-purine diet is not clear

People who develop uric acid stones often have gout or diabetes. Uric acid is a waste product generated by substances called purines. Purines are mainly produced by the body itself, but are also found in some foods. This is the reasoning behind recommending a low-purine diet with less fish, meat and seafood to prevent uric acid stones from forming.

There has not yet been any scientific research to test whether a low-purine diet can lower the risk of developing uric acid stones. So it's not clear what can be expected from this kind of diet.

When is medication for preventing kidney stones a good option?

Medication for preventing kidney stones is an option for people who are at a greater risk of having more kidney stones.

Any of the following things may be a sign of a higher risk:

  • Kidney stones that develop in childhood or early adulthood
  • Family history of kidney stones
  • Medical conditions affecting the kidneys, urinary tract or gastrointestinal tract
  • Overactive parathyroid
  • Kidney stones associated with a urinary tract infection
  • Uric acid stones
  • Cystine stones (caused by a rare inherited metabolic disorder)

The cause will determine what type of medication should be used. These include the following:

  • Potassium citrate: This lowers the acidity of the urine, improving its ability to dissolve salts. Potassium citrate is commercially available in dissolvable tablet, capsule, and powder form. It is used to prevent calcium stones, uric acid stones and cystine stones.
  • Thiazide diuretics: These medications reduce the amount of calcium entering the bloodstream. They promote the production of urine, preventing calcium stones.
  • Allopurinol: This drug inhibits the breakdown of purines to uric acid, lowering the uric acid levels in the urine. Allopurinol is mostly used to prevent uric acid stones.
  • Other medications: Medications that increase the acidity of the urine (L-methionine) can be used to prevent kidney stones caused by urinary tract infections. Dietary supplements with magnesium increase the levels of magnesium in the urine. There it binds with oxalate and is believed to prevent the formation of calcium oxalate stones.

Doctors can use blood and urine tests as well as an analysis of the kidney stones to decide which of the preventive medications would be most suitable.

Medications for preventing kidney stones are taken once a day for life. They're usually only considered if someone has already had kidney stones at least twice.

How effective are the medications used for prevention?

Studies have shown that the commonly used medications effectively prevent more kidney stones from developing.

Potassium citrate

Several studies have shown that potassium citrate is effective in preventing kidney stones:

  • Without potassium citrate, 53 out of 100 people had another kidney stone within two years.
  • With potassium citrate, 13 out of 100 people had another kidney stone within two years.

The possible side effects of potassium citrate are gastrointestinal problems and diarrhea. About 13 out of 100 people in the studies stopped their treatment early due to the side effects.

Thiazide diuretics

Research has also shown that thiazide diuretics are effective:

  • Without thiazide diuretics, 47 out of 100 people had another kidney stone within three years.
  • With thiazide diuretics, 24 out of 100 people had another kidney stone within three years.

Thiazide diuretics can have various side effects, including low blood pressure accompanied by dizziness and drowsiness, a dry mouth and erectile dysfunction. 8 out of 100 people in the studies stopped their treatment early due to side effects.

Allopurinol

Allopurinol is mostly used to prevent uric acid stones. Its effectiveness has only been tested in research involving people with calcium stones though. Those studies showed that allopurinol can prevent calcium stones:

  • Without allopurinol, 55 out of 100 people had another kidney stone within three and a half years.
  • With allopurinol, 33 out of 100 people had another kidney stone within three and a half years.

Allopurinol may cause rashes and sometimes trigger gout attacks. But in the studies, the number of people who dropped out due to side effects was no greater in the group that had the allopurinol treatment than in the group that did not.

Other medications

Other types of medications used for the prevention of specific types of kidney stones, such as magnesium or L-methionine, have not yet been tested in good-quality studies, so it's still not clear whether they can effectively prevent kidney stones.

Sources

  • Fink HA, Wilt TJ, Eidman KE, Garimella PS, MacDonald R, Rutks IR et al. Medical management to prevent recurrent nephrolithiasis in adults: a systematic review for an American College of Physicians Clinical Guideline. Ann Intern Med 2013; 158(7): 535-543. [PubMed: 23546565]
  • Fink HA, Wilt TJ, Eidman KE, Garimella PS, MacDonald R, Rutks IR et al. Recurrent Nephrolithiasis in Adults: Comparative Effectiveness of Preventive Medical Strategies. Agency for Healthcare Research and Quality (AHRQ); July 2012.
  • IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

    Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. We do not offer individual consultations.

    Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

© IQWiG (Institute for Quality and Efficiency in Health Care)
Bookshelf ID: NBK348941

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