ACP Recommendations for Recurrent Nephrolithiasis

A systematic literature review conducted by the American College of Physicians (ACP) to develop a clinical practice guideline for the dietary and pharmacologic management to prevent nephrolithiasis in adults resulted in 2 recommendations [Ann Intern Med. 2014;161:659-667].

To prevent recurrent nephrolithiasis, the ACP recommended increased fluid intake throughout the day to achieve at least 2 liters of urine per day. In patients with active disease in whom increased fluid intake fails to reduce the formation of stones, the ACP recommended pharmacologic monotherapy with a thiazide diuretic, citrate, or allopurinol.

The guideline was developed to present the available evidence to all clinicians on the comparative effectiveness and safety of preventive dietary and pharmacologic management for recurrent (>1 prior kidney stone episode) nephrolithiasis in adults.

Evidence was obtained through a systematic review of the literature that included English-language trials identified through MEDLINE and the Cochrane Database of Systemic Reviews between January 1948 and September 2012, as well as Google Scholar, ClinicalTrials.gov, and Web of Science from January 1984 to March 2014.

Clinical outcomes assessed included pain, urinary tract obstruction with acute renal impairment, stone recurrence, infection, procedure-related illness, hospitalizations, emergency room visits, quality of life, and end-stage renal disease.

Interventions evaluated included dietary (ie, increased fluid intake, increased oligomineral water intake, decreased soft drink intake, multicomponent dietary interventions, high fiber intake, and low animal protein intake) and pharmacologic (ie, thiazide diuretic, citrate, allopurinol, acetohydroxamic acid, and magnesium).

To grade the quality of the evidence, the guideline used the ACP Guideline Grading System. A strong recommendation was based on evidence in which the benefits clearly outweighed the risks and burden or risks and burden clearly outweighed the evidence. A weak recommendation was based on benefits finely balanced with risks and burden.

The recommendation to increase fluid intake was based on low-quality evidence that showed an association between increased fluid intake and reduced stone recurrence. No difference was seen
between tap water and specific brands of mineral water.

Low-quality evidence also showed a reduced risk of stone recurrence and decreased consumption of soft drinks, but only for soft drinks acidified by phosphoric acid, such as colas.

The recommendation for pharmacologic monotherapy with a thiazide diuretic, citrate, or allopurinol was based on moderate-quality evidence that showed these agents reduced the risk of stone recurrence of composite calcium stones. No added benefit was found when combining agents.

The authors of the guideline noted that in the available evidence, higher doses of thiazides were evaluated (ie, hydrochlorothiazide 50 mg, chlorthalidone 25 mg or 50 mg, indapamide 2.5 mg) to prevent recurrent nephrolithiasis. Undetermined from the evidence is whether lower doses are as effective as higher doses to prevent stone recurrence.

Inconclusive from the current evidence is the relationship between pretreatment and in-treatment stone composition and biochemistry with treatment efficacy to prevent stone recurrence, according to the researchers.

As with all guidelines, the authors noted that “clinical practice guidelines are ‘guides’ only and may not apply to all patients and all clinical situations. Thus, they are not intended to override clinicians’ judgment.”—Mary Beth Nierengarten