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Long-term prevention of kidney stones is possible for most patients. For starters, patients must drink a lot of water and follow low sodium, normal calcium diets.
People who have had more than one kidney stone are likely to form another. Without proper treatment to prevent recurrence, the rate is as high as 50% in the first five years and 80% in ten years. Fortunately, there are things that can be done to dramatically improve the odds.
The first step is to identify the stone. The four types are:
| Type |
Incidence |
Cause |
| Calcium |
75 to 80% of cases |
Calcium and/or oxalate or phosphate |
| Struvite |
10 to 15% of cases |
Infection in the urinary tract |
| Uric acid |
5 to 10% of cases |
Uric acid (a by-product of protein metabolism) |
| Cystine |
1% of cases |
Cystinuria (a hereditary condition) |
A doctor will do in-depth family and medical histories, a physical exam, common urine and blood tests and a 24-hour urine collection test to measure urine volume and levels of acidity, calcium, sodium, uric acid, oxalate, citrate and creatinine. If the patient was able to catch a stone when it passed, it can be analyzed.
The most important step to prevent kidney stones of any type is to drink enough liquid throughout the day to produce at least 2 quarts of urine in every 24-hour period. Water is best. Soft drinks may acidify the urine and contribute to stone formation. More fluid is needed after exertion, during warm weather and during times of stress.
In addition, once the cause of the stone is found, medications or changes in diet may be used to help prevent new stones.
In general, scientists don't think that eating any specific foods causes stones to form in people who are not already susceptible. In susceptible people, however, diet changes appear to help. Depending on the type of stone, recommended changes might include:
- Limiting meat protein to eight ounces a day
- Reducing foods high in oxalate, such as spinach, okra, beets and rhubarb
- Increasing fiber-rich foods
- Restricting salt intake to less than 2,000 mg per day
Restricting calcium intake is NOT recommended. In fact, doing so might actually increase the risk of forming kidney stones since dietary calcium helps to bind up oxalate in the colon. Doctors generally recommend a diet with normal amounts of calcium.
Some people will need medication to prevent stones from forming. The choice of medicine depends on the type of kidney stone.
- Thiazides reduce the amount of calcium in the urine, which may prevent calcium kidney stones.
- Calcium carbonate and calcium citrate may be used to prevent kidney stones in people with high levels of oxalate.
- Orthophosphate helps prevent calcium stones that do not contain a lot of oxalate.
- Medications that prevent the urine from becoming too acidic help prevent uric acid stones.
The good new is that doctors have achieved very high success rates at preventing kidney stones with patients who are compliant (they faithfully follow fluid intake, diet and medication regimens).
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