In order to reduce his risk of forming more stones, you tell him to incorporate all of the following lifestyle changes EXCEPT:
ExplanationThe correct answer is A. To prevent recurrent urolithiasis, restricted calcium intake was encouraged in the past. Now, moderate calcium intake (1 g/day) is recognized as beneficial and should be encouraged. Patients should take calcium with meals, which will bind oxylate and prevent its absorption. A low-calcium diet permits greater absorption of oxalate in the intestines, possibly leading to hyperoxaluria and an increased risk of urolithiasis. Increases in urine oxalate greatly increase the risk of stone formation. Restriction of oxalate (answer B) in the diet may help to reduce the risk of recurrent urolithiasis. Unfortunately, oxalate is also the end product of numerous metabolic pathways, and significant reduction in urinary oxalate levels often proves difficult. Increased fluid intake (answer C) to achieve a urine volume >2 L/day reduces stone formation. Water and citrus juices are traditionally recommended, but most fluids consumed are associated with a positive effect, including drinks with caffeine. Meat, fish, and poultry are sources of purine, which is metabolized to uric acid. A uric acid crystal can form a pure uric acid stone or serve as a nidus for calcium stone formation. Therefore, a general recommendation to avoid recurrent urolithiasis is to reduce purines in the diet by reducing meat, fish, and poultry consumption (answer D). Urinary citrate inhibits calcium stone formation. Hypocitraturia is a common cause of recurrent urolithiasis.
