Diagnosis and treatment of calcium kidney stones.

Calcium oxalate nephrolithiasis is a common syndrome that recurs and may be complicated by infection, obstruction, bleeding, and rarely, impairment in renal function. The formation of Ca oxalate stones depends on the state of urinary supersaturation with respect to Ca and oxalate and the action of urinary inhibitors of crystal nucleation, aggregation, and growth. Idiopathic hypercalciuria is the most common cause of Ca oxalate stones and is characterized by hypercalciuria, normocalcemia, and intestinal Ca hyperabsorption with or without elevated serum 1,25(OH)2D3 levels in the absence of other known causes of hypercalciuria. Current diagnostic evaluation of recurrent Ca oxalate nephrolithiasis should be conducted while the patients follow their usual diets and includes the following: 1. Analysis of stone composition by polarization microscopy. 2. Measurement of serum Ca, phosphate, uric acid, 1,25(OH)2D3, and creatinine. 3. Twenty-four-hour urine collection for an analysis of volume, pH, and excretion of Ca, phosphorus, magnesium, uric acid, citrate, sodium, oxalate, and creatinine. Therapy to prevent stone recurrence is designed to reduce urinary supersaturation of Ca oxalate by increasing urine volume, reducing urine Ca to below 200 mg/24 hr with thiazide, maintaining dietary Ca intake at 600 to 800 mg/day, and adding potassium citrate if urine citrate levels are reduced. If elevated, urine oxalate excretion can be reduced by dietary oxalate restriction. Stones less than 2 cm in diameter located in the renal parenchyma or upper urinary tract can be fragmented with ESWL, whereas larger stones or those in the lower urinary tract should be removed by either percutaneous nephrolithotomy or ureteroscopic procedures.