The Modern Realities of Kidney Stones: Preventing Reoccurrence

Q) A patient recently came in after an episode of kidney stones. He said he had never experienced such pain before (and this is a former Army Ranger!) and asked if there was anything he could do to keep it from happening again. I told him what I had learned in school (lots of fluids, no organ meats), but is there anything new?

Your patient has some reason for concern. For people who have had a symptomatic kidney stone, the likelihood of developing another within five years is 35% to 50% if no preventive action is taken. ¹ Certain factors—including family history, younger age at onset, and predisposing medical conditions (eg, hyperparathyroidism, diabetes, obesity, gout)—increase risk for recurrence. ^2,3

In the past, patients were often advised to restrict their dietary calcium intake to prevent calcium oxalate and/or calcium phosphate stones. However, more recent research has proven the opposite to be true: People with lower dietary calcium intake can be at greater risk for kidney stones. ^1-3 Therefore, encourage patients to consume about 800 to 1,200 mg/d of dietary calcium. Oral supplementation does not seem to yield the same protective benefits as dietary calcium. This may be related to absorption. ¹

Diets high in oxalates (eg, chocolate, nuts, spinach) can increase risk for stone formation, particularly in patients who have bowel diseases that cause inflammation or a history of a bowel resection. ² Animal protein in the diet can cause hypercalcinuria and increased uric acid levels, which is particularly problematic for individuals with gout or inflammatory arthritis. High-sodium diets can cause higher urinary calcium oxalate levels, while diets high in phosphorus (particularly dark cola soft drinks) can increase risk for stone formation. Advise your patient to avoid foods high in oxalates, animal proteins, sodium, and phosphorus. ²

Dehydration, either due to exercise or poor fluid intake, can result in concentrated urine, which facilitates stone formation. While opinions differ on the benefits of certain dietary restrictions, most research supports the idea that generous fluid intake is the most successful intervention in preventing recurrence of stone formation (regardless of underlying cause). Diluting the urine decreases the concentration of solutes responsible for stone formation. ^1-3

If the conservative measures of dietary restriction and adequate hydration fail, medications may be beneficial, depending on stone type or underlying metabolic condition. Thiazide diuretics can help lower urinary calcium by enhancing reabsorption of calcium from the distal convoluted tubule and sodium excretion; however, they should be used cautiously due to the risk for adverse effects such as dizziness and lightheadedness. ^1,3 Allopurinol can lower uric acid levels, decreasing recurrence of both uric acid and calcium oxalate stones. Hypocitraturia is prevalent in 20% to 60% of persons with stones; prescribing potassium citrate can inhibit crystal growth of calcium phosphate and calcium oxalate in urine. ²

To help patients prevent stone recurrence, perform a comprehensive assessment of their dietary and lifestyle habits and medical history to identify possible contributing factors. Educate patients on adequate dietary calcium intake, generous water intake to keep urine dilute, and avoidance of dietary triggers.