Fast Five Quiz: Kidney Stones (Renal Calculi)

Vecihi Batuman, MD

Disclosures

May 12, 2021

In almost all patients in whom stones form, an increase in fluid intake and, therefore, an increase in urine output is recommended. This is probably the single most important aspect of stone prophylaxis. Patients with recurrent nephrolithiasis traditionally have been instructed to drink eight glasses of fluid daily to maintain adequate hydration and decrease chance of urinary supersaturation with stone-forming salts. The goal is a total urine volume in 24 hours in excess of 2.5 L.

The AUA guidelines state that patients with uric acid stones or calcium stones and relatively high urinary uric acid levels should be counseled that limiting intake of nondairy animal protein may help reduce stone recurrence.

Dietary calcium should not be restricted beyond normal (1000-1200 mg/d) unless specifically indicated on the basis of on 24-hour urinalysis findings. Urinary calcium levels are normal in many patients with calcium stones. Reducing dietary calcium in these patients may worsen their stone disease because more oxalate is absorbed from the gastrointestinal tract in the absence of sufficient intestinal calcium to bind with it. This results in a net increase in oxalate absorption and hyperoxaluria, which tends to increase new kidney stone formation in patients with calcium oxalate calculi. Patients with calcium oxalate stones and relatively high urinary oxalate levels should consider limiting intake of oxalate-rich foods (eg, beans, berries, dark green vegetables) and maintain normal calcium consumption.

Read more about dietary approaches in patients with renal calculi.

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