Medical Management of Calcium Phosphate Stones

Initial Evaluation

• The American Urological Association recommends obtaining a stone analysis at least once to confirm calcium phosphate composition 3
• Metabolic testing with 24-hour urine collections analyzing volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine should be performed 4
• Review imaging studies to quantify stone burden 3

Dietary Modifications

• Increase fluid intake to achieve urine volume of at least 2.5 liters daily 5, 6
• Limit sodium intake to 2,300 mg (100 mEq) daily to reduce urinary calcium excretion 6
• Maintain normal dietary calcium intake of 1,000-1,200 mg per day (avoid calcium restriction) 6
• Consume ample fruits and vegetables to help counterbalance acid load 7
• Avoid sugar-sweetened beverages which may increase stone risk 6

Pharmacological Management

• Thiazide diuretics are recommended for patients with high or relatively high urine calcium and recurrent calcium stones 1, 7
• Potassium citrate therapy is recommended for patients with low or relatively low urinary citrate 7, 2
• Consider combination of thiazides and potassium citrate for patients with persistent stone formation despite addressing individual metabolic abnormalities 2

Follow-up

• Monitor response to therapy with repeat 24-hour urine collections 4
• Adjust therapy based on changes in urinary parameters and clinical response 2
• Inadequate fluid intake remains a major risk factor for stone recurrence regardless of other interventions 5
• Calcium restriction can worsen stone formation and should be avoided 6