The American College of Physicians (ACP) has issued new, evidence-based guidelines on the comparative efficacy and safety of dietary and pharmacologic strategies to prevent recurrent kidney stones in adults.

The updated recommendations, published by Amir Qaseem, MD, PhD, from the ACP, and colleagues in the November 4 issue of the Annals of Internal Medicine, include dietary changes such as increased fluid intake to achieve at least 2 L of urine per day, which was a weak recommendation based on low-quality evidence.

“Increased fluid intake spread throughout the day can decrease stone recurrence by at least half with virtually no side effects,” ACP President David Fleming, MD, said in a news release. “However, people who already drink the recommended amount of liquids, or when increased fluid intake is contraindicated, should not increase their fluid intake.”

Available evidence showed no difference between intake of tap water or intake of a specific brand of mineral water in preventing kidney stones.

If drinking increased amounts of water is ineffective in preventing kidney stones, the guidelines recommend pharmacologic monotherapy with a thiazide diuretic, citrate, or allopurinol. This is a weak recommendation based on moderate-quality evidence.

Research to date indicates that these three types of drugs effectively reduced recurrence of composite calcium stones in patients who had a history of two or more stones. Combination therapy was no more effective than monotherapy, but there were no head-to-head comparisons of these drugs.

All these drugs were associated with adverse events. For thiazides, these were orthostasis, gastrointestinal upset, erectile dysfunction, fatigue, and muscle symptoms. Citrates were associated with gastrointestinal symptoms and allopurinol with rash, acute gout, and leukopenia.

Other dietary recommendations in the guidelines include the following:

• Patients should reduce intake of colas and other soft drinks acidified with phosphoric acid, as lower consumption is linked to lower risk for stone recurrence. Fruit-flavored soft drinks are preferable, as they are often acidified with citric acid.
• Patients should reduce consumption of dietary oxalate, typically found in chocolate, beets, nuts, rhubarb, spinach, strawberries, tea, and wheat bran.
• Patients should eat less dietary animal protein and purines.
• Patients should maintain normal dietary calcium.

The ACP guidelines panel reviewed published English-language literature from 1948 through March 2014, identified using a search of MEDLINE, the Cochrane Database of Systematic Reviews, Google Scholar, ClinicalTrials.gov, and Web of Science. Evaluated outcomes included symptomatic stone recurrence, pain, urinary tract obstruction with acute renal impairment, infection, procedure-related illness, emergency department visits, hospitalizations, quality of life, and end-stage renal disease.

Lifetime prevalence of kidney stones in the United States is approximately 13% in men and 7% in women. Without treatment, approximately 35% to 50% of those with kidney stones will experience recurrence within 5 years from the first stone.

“Almost all studies analyzed in the evidence review included only patients with calcium stones, which are the most common stone type,” the guidelines authors conclude. “Although biochemistry suggests a relationship between pharmacologic method of action and stone type, no randomized, controlled trials link biochemical testing to outcomes.”

The authors have disclosed no relevant financial relationships.

Ann Intern Med. 2014;161:659-667. Full text

Story Source