Prevention of Recurrent Nephrolithiasis in Adults

TO THE EDITOR:

Qaseem and colleagues' (1) recommendation to drink at least 2 L of fluid per day and use thiazide diuretics, citrate, or allopurinol when fluids alone are insufficient mirror a recent guideline released by the American Urological Association. However, several features of the American College of Physicians' recommendations disagree with those of the American Urological Association. For example, Qaseem and colleagues do not recommend baseline evaluation of stone composition or 24-hour urine analysis for stone risk factors. Kidney stone analysis by infrared spectroscopy is relatively inexpensive; very precise; and, in our opinion, essential to properly diagnose the form of kidney stone disease. A thiazide diuretic would not be helpful for a patient with uric acid kidney stones or someone with cystinuria, both of which can be determined by stone analysis alone. Furthermore, 24-hour urine analysis can help to guide logical therapeutic choices and specific dietary advice for an individual patient. For example, pharmacotherapy may not help persons in whom a very low urine volume is the only major risk factor and those with enteric hyperoxaluria need specific therapy geared toward dietary measures to reduce oxalate loads. In these cases, allopurinol or thiazide would probably not have any benefit.