Secondary prevention
Metabolic abnormalities contributing to stone formation may be detected in the 24-hour urine stone risk profiles and may be modified by diet or medications. Dietary modifications may be suggested in an attempt to prevent future calculi. No studies on dietary or medical therapy have been performed specifically on patients with MSK given the rarity of this condition. The only randomised controlled trial (RCT) of a diet successful for prevention of stones in patients with hypercalciuria consisted of significantly restricting sodium (to limit calcium excretion), restricting animal protein, restricting oxalate, and increasing dietary calcium to at least 1200 mg daily. This diet decreased stone recurrence by nearly 50% compared with the control group, which was dietary calcium and oxalate restriction alone.[42] Additionally, one study of individuals with and without a history of kidney stones found that a Dietary Approaches to Stop Hypertension (DASH)-style diet may reduce stone risk by increasing urinary citrate and volume.[49] Thiazide diuretics decrease stone recurrence in hypercalciuric patients.[45][46] Thiazides and diet have not been compared for their relative success or adherence. Patients with hyperoxaluria should avoid both high-oxalate foods and severe dietary calcium restriction (may be inadvertent in low-cholesterol diets, lactose intolerance, and kosher diets), which will decrease binding of oxalate in the gastrointestinal tract, promoting hyperoxaluria and increased stone formation. Successful studies of diet for hyperoxaluria are still lacking; increasing dietary calcium may be more important than restricting dietary oxalate intake. Hypocitraturic patients may be treated with potassium citrate. This therapy has been shown in one RCT to decrease calcium stone recurrence in hypocitraturia.[40] Citrate supplementation may be successful even if hypocitraturia is not present and may be useful when adherence to higher fluid intake or dietary restrictions has failed. Hyperuricosuric patients with calcium stones may be treated with dietary purine restriction and allopurinol or febuxostat if urine uric acid >800 mg/day.[41] Patients with distal renal tubular acidosis have impairment in acid excretion, leading to metabolic acidosis with alkaline urine, which predisposes to calcium phosphate stone formation. Hypercalciuria should be addressed with salt restriction and thiazides, and hypocitraturia, with potassium citrate.
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