Preventing Kidney Stones

The American College of Physicians has just released recommendations for people who have had kidney stones (Ann Intern Med, November 4, 2014;161(9):659-667). Thirteen percent of North American men and seven percent of women suffer from kidney stones, which can be incredibly painful as stones pass from the kidneys to the outside. Those who get one stone have a 50 percent chance of passing another stone in five years.

Eighty percent of kidney stones contain calcium oxalate, calcium phosphate, or both. Other stones consist of struvite, uric acid, or cystine. Surprisingly, a review of 36 studies shows that stone recurrence is not prevented by assessing the chemical type of stone or doing blood and urine chemistries other than calcium levels. Here are the current recommendations for preventing kidney stones:



• Drink enough water to make you urinate at least eight cups of urine per day. Strong evidence shows that this is the most effective step in preventing kidney stones. Do not waste your money on expensive low-mineral waters; they offer no advantage over ordinary tap water.



• Avoid soft drinks that contain phosphoric acid, which increases stone formation. Read the labels. Drinks that are acidified with citric acid (fruit-flavored sodas) are far less likely to cause stones.



• Restrict animal proteins (meat, poultry and fish); they contain purines that can bind to calcium to form stones.



• Restrict salt



• Restrict foods high in oxalates, such as chocolate, beets, nuts, rhubarb, spinach, strawberries, tea, and wheat bran. Oxalates can bind to calcium to form calcium oxalate stones.



• People who have had more than one attack of painful kidney stones may want to consider taking thiazide diuretics, citrate or allopurinol. Taking all three drugs has not been shown to be more beneficial than taking just one. No data exist to show that one thiazide diuretic is better than any other. Thiazide diuretics can cause dizziness, belly cramps, fatigue, and muscle cramps. Citrates can cause belly cramps, and allopurinol can cause a low white blood cell count. Check with your doctor.



• Magnesium pills have not been shown to prevent kidney stones.



• We have no data to show that a high-fiber diet helps to prevent kidney stones, although it may.



• Check blood and urine levels of calcium. Having high blood  or urine calcium can cause kidney stones. It may also be a good idea for people with recurrent kidney stones to get a blood test called parathyroid hormone to check for a highly-curable parathyroid tumor.

See NIH's Diet for Kidney Stone Prevention

Checked 8/1/18

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