Kidney Int：3或4期CKD患者使用碳酸钙有质疑

　　美国一项研究表明，3或4期慢性肾脏病（CKD）患者或不应使用碳酸钙作为磷酸盐结合剂，以期减少磷潴留、预防负钙平衡。研究中安慰剂组表现为钙、磷平衡；碳酸钙组表现为正钙平衡，几乎不影响磷平衡，且存在钙软组织沉积（图）。该论文发表于《国际肾脏》杂志。

　　注：（a）CKD患者由于胃肠道吸收功能欠佳，在摄入常规剂量钙时处于负钙平衡，从而导致继发性甲状旁腺功能亢进，并出现进行性骨质脱钙；（b）CKD患者补充大剂量钙，出现正钙平衡，且幅度随时间推移逐渐降低，在大剂量补钙初期，钙质主要沉积于骨，随时间推移，逐渐转为沉积于软组织。

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Oral calcium carbonate affects calcium but not phosphorus balance in stage 3–4 chronic kidney disease
Abstract
Patients with chronic kidney disease (CKD) are given calcium carbonate to bind dietary phosphorus, reduce phosphorus retention, and prevent negative calcium balance; however, data are limited on calcium and phosphorus balance during CKD to support this. Here, we studied eight patients with stage 3 or 4 CKD (mean estimated glomerular filtration rate 36 ml/min) who received a controlled diet with or without a calcium carbonate supplement (1500 mg/day calcium) during two 3-week balance periods in a randomized placebo-controlled cross-over design. All feces and urine were collected during weeks 2 and 3 of each balance period and fasting blood, and urine was collected at baseline and at the end of each week. Calcium kinetics were determined using oral and intravenous 45calcium. Patients were found to be in neutral calcium and phosphorus balance while on the placebo. Calcium carbonate supplementation produced positive calcium balance, did not affect phosphorus balance, and produced only a modest reduction in urine phosphorus excretion compared with placebo. Calcium kinetics demonstrated positive net bone balance but less than overall calcium balance, suggesting soft-tissue deposition. Fasting blood and urine biochemistries of calcium and phosphate homeostasis were unaffected by calcium carbonate. Thus, the positive calcium balance produced by calcium carbonate treatment within 3 weeks cautions against its use as a phosphate binder in patients with stage 3 or 4 CKD, if these findings can be extrapolated to long-term therapy.