ACP releases new recommendations to prevent recurrent kidney stones
In a new evidence-based clinical practice guideline published today in Annals of Internal Medicine, the American College of Physicians (ACP) recommends that people who have had a kidney stone increase their fluid intake to achieve at least two liters of urine per day to prevent another kidney stone from forming. If increased fluid intake fails to reduce the formation of stones, ACP recommends adding medication with a thiazide diuretic, citrate, or allopurinol.
"Increased fluid intake spread throughout the day can decrease stone recurrence by at least half with virtually no side effects," said Dr. David Fleming, president, ACP. "However, people who already drink the recommended amount of liquids, or when increased fluid intake is contraindicated, should not increase their fluid intake."
The evidence did not show any difference between tap water compared to a specific brand of mineral water. The evidence indicated that a decrease in consumption of soft drinks acidified by phosphoric acid, such as colas, is associated with a reduced risk of stone recurrence. (Fruit-flavored soft drinks are often acidified by citric acid.)
The evidence showed that thiazide diuretics, citrates, or allopurinol effectively reduced recurrence of stones formed of calcium—the most common type of kidney stone—in patients with at least two past stones. No studies directly compared the drugs to each other.
The guideline authors note that doctors also recommend dietary changes to prevent recurring kidney stones, including reducing dietary oxalate (e.g., chocolate, beets, nuts, rhubarb, spinach, strawberries, tea, and wheat bran), reducing dietary animal protein and purines, and maintaining normal dietary calcium.
A kidney stone occurs when tiny crystals in urine stick together to form a stone. About 13 percent of men and 7 percent of women in the United States will develop a kidney stone during their lifetime. Studies show that the recurrence rate of kidney stones within five years of an initial stone ranges from 35 to 50 percent without treatment.
ACP's recommendations are based on published literature in the English language on this topic from 1948 through March 2014.