Kidney stones
Description
An in-depth report on the causes, diagnosis, treatment, and prevention of kidney stones.
Alternative Names
Calcium stones; Nephrolithiasis
Medications
Diuretics.
Diuretics are commonly used in the treatment of high blood pressure and other disorders to eliminate fluid and sodium from the body. Low doses of diuretics known as thiazides are sometimes used to reduce the amount of calcium released by the kidneys into the urine. Thiazides include:
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Hydrochlorothiazide (Esidrix, HydroDiuril)
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Chlorothiazide (Diuril)
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Trichlormethiazide (Metahydrin, Naqua)
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Chlorthalidone (Hygroton)
However, thiazides also cause potassium loss, which reduces citrate levels and can increase the risk for stones. Potassium citrate should be taken with a thiazide to prevent citrate loss. Amiloride (Midamor) is a potassium-sparing diuretic, which may be used if a thiazide does not work.
Citrates.
Citrate salts are often given to people with calcium oxalate or uric acid stones:
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Potassium magnesium citrate is available over the counter. It is proving to be very beneficial in preventing kidney stones. In one study, potassium magnesium citrate reduced the risk for kidney stone recurrence by 85%.
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Potassium citrate (K-Lyte, Polycitra-K, Urocit-K) is given as the only treatment to people with normal urine calcium levels. Between 70 - 75% of patients with recurrent stones have experienced on-going remission with potassium citrate therapy. Some people cannot tolerate potassium citrate because of side effects (stomach problems).
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Magnesium citrate (Citroma, Citro-Nesia) may be useful for people who develop calcium stones from impaired intestinal absorption due to small bowel disease.
None of these products should be used by people with struvite stones, urinary tract infections, bleeding disorders, or kidney damage. Patients who take citrate supplements containing potassium should not take any other medications that either contain the mineral or prevent its loss (such as so-called potassium-sparing diuretics). People with peptic ulcers should avoid them or discuss using non-tablet forms with their doctor.
Phosphates.
Phosphates help reduce the breakdown of bone that releases calcium into the bloodstream. They are also involved in reabsorption of calcium from urine by the kidney.
Phosphate compounds:
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Neutral (nonacidic) sodium or potassium phosphate (K-Phos, Neutral, Neutra-Phos) is usually taken four times a day after meals to prevent kidney stones unless otherwise directed by the doctor. Diarrhea is a possible side effect.
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Cellulose phosphate (Calcibind) is recommended only for severe hypercalciuria caused by excessive absorption of calcium from the intestines that is associated with recurrent calcium stones. However, this drug may increase oxalate levels and decrease magnesium levels, which can lead to stones. Restricting dietary oxalates, calcium, and ascorbic acid, and taking magnesium supplements may help offset these risks. Cellulose phosphate may also cause bloating.
Acidic forms of phosphate should not be used, since they increase the risks for both hypocitraturia and hypercalciuria.
Cholestyramine.
Cholestyramine (Questran, Questran Light) is a drug used to reduce cholesterol levels. However, it also binds with oxalate in the intestine, so it is used to reduce elevated oxalate levels in urine (hyperoxaluria). The drug is usually taken in powder form, dissolved in water, milk, or fruit juice; it is also available as a chewable bar (Cholybar). Bloating and constipation are common side effects of this drug. The drug also interferes with other medications, including digoxin (Lanoxin) and warfarin, and may contribute to calcium loss and osteoporosis. In order to prevent such interactions, other drugs should be taken one hour before or 4 to 6 hours after taking cholestyramine. If the drug is taken for a long period of time, deficiencies of vitamins A, D, E, and K can result. Vitamin supplementation may be necessary.
Medications for Uric Acid Stones
Sodium Bicarbonate.
Patients whose uric acid stones are caused by persistently acidic urine may take sodium bicarbonate to reduce acidity. Patients taking sodium bicarbonate must test their urine regularly with pH paper, which turns different colors depending on whether the urine is acidic or alkaline. Too much sodium bicarbonate can cause the urine to become overly alkaline and increase the risk for calcium phosphate stones. This treatment should not be used by patients who need to restrict sodium for other medical conditions.
Potassium Citrate.
Potassium citrate, which restores citrate to the urine, is useful for patients with high levels of uric acid in the urine.
Allopurinol.
Allopurinol (Lupurin, Zyloprim) is very effective in reducing high levels of uric acid and may be helpful for patients with uric acid stones. Allopurinol will
not
prevent calcium stones from forming. There is also a slight risk for xanthine stones with this drug. Side effects include diarrhea, headache, and fever. More severe complications include blood disorders that may produce fatigue, bleeding, or bruising. About 2% of patients experience an allergic reaction to allopurinol that causes a rash. In rare cases, the rash can become severe and widespread enough to be life threatening. Allergic individuals who had experienced only a mild rash to sodium bicarbonate may be able to build up their tolerance for the drug by undergoing a desensitization process. The drug may also increase the risk for cataracts.
Allopurinol reduces uric acid levels rapidly, so it may trigger an attack of gout in susceptible people. To prevent this, patients taking allopurinol should also take a nonsteroidal anti-inflammatory (NSAID) for 2 or 3 months. Aspirin should not be taken, since it increases uric acid levels. Patients should discuss the appropriate drug with their doctor.
Medications for Struvite Stones
Before any medical treatment is given for struvite stones, the stones must be completely removed with surgery.
Antibiotics for Eliminating Infection.
Persons with struvite stones are given on-going antibiotics to keep the urine free of the bacteria that cause urinary tract infections. Careful follow-up and urine testing is extremely important. (A high pH urine indicates low acidity and an increased risk of infection.)
Acetohydroxamic Acid (AHA).
Acetohydroxamic acid (AHA or Lithostat) is beneficial when used with long-term antibiotics. AHA blocks substances that are released by bacteria and has been effective in preventing stones even when bacteria are present. Side effects, however, can be severe. The drug reduces iron in the body, so anemia is a common problem. Iron supplements may be needed. Other side effects include nausea, vomiting, depression, anxiety, rash, persistent headache, and, rarely, small blood clots in the legs. Experts recommend this drug only for patients with healthy kidneys who have chronic diseases caused by these specific struvite-causing organisms. Alcohol should be avoided. Pregnant women should not take acetohydroxamic acid.
Organic Acids.
Medical treatments to dissolve stones may be useful with in patients who do not respond to other medications, or in combination with surgeries. Acidic urine dissolves struvite stones, so the doctor may wash the urinary tract with a solution of organic acids (e.g., Renacidin). Candidates for irrigation must have sterile urine and healthy kidney function. In surgical patients, irrigation is performed 4 or 5 days after the operation. The urinary tract is washed with saline for 1 to 2 days and, if there are no problems, the organic acid solution is given for another 1 or 2 days until all stones are dissolved. The patient's urine should be tested on a regular basis to be sure that bacteria does not return.
Aluminum Hydroxide Gel.
An aluminum hydroxide gel anti-acid may reduce phosphate levels but it carries a long-term risk of aluminum toxicity. Prolonged depletion of phosphorus can also increase the risk for calcium oxalate stones. Experts recommend limiting phosphorus through a low-protein diet.
Medications for Cystine Stones
The first-line treatment for cystine stones is increasing the alkalization of urine so the stone can dissolve. If alkalization fails, drugs such as d-penicillamine, alpha-mercaptopropionylglycine (tiopronine), or captopril may be used to lower cystine concentration. Fluid intake for cystine stones must be even more voluminous than for regular stones. The patient should uniformly drink at least four quarts of water over a 24-hour period.
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Review Date: 5/22/2006
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Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital
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