Sixteen patients with absorptive hypercalciuria and nephrolithiasis ate a low-calcium diet and were given cellulose phosphate (5 g twice to three times per day orally). In all 16 cases urinary calcium decreased, usually to values below 200 mg per day, and in 13 cases, the state of saturation of urine with respect to brushite (the nidus of calcium stones) also decreased, often from supersaturation to undersaturation. Clinically, renal-stone formation virtually ceased. The treatment was well tolerated, and no serious side effects have been observed. Serum concentration of parathyroid hormone and bone density by 125 I-photon absorption did not change significantly or remained within the normal range. Thus, in these patients with an enhanced intestinal absorption of calcium, hypercalciuria may be corrected, and stone formation prevented, by a low-calcium diet and inhibition of calcium absorption with cellulose phosphate. THE problem of recurrent nephrolithiasis presents a considerable challenge from the standpoint of both pathogenesis and treatment. The majority of calcium-containing renal stones probably develop by crystal growth from the nidus of brushite (CaHPO4·2H2O), which is formed in an organic matrix, 1 or by spontaneous precipitation. 2 Brushite probably serves as the nidus for stones of calcium phosphate and for certain stones of calcium oxalate. 3 The nidus of brushite may form when the urine specimens are “oversaturated” 4 with respect to brushite — that is, when the extent of supersaturation exceeds the metastably supersaturated state. It cannot form from.
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