Pro/Con debate: the calculation on calcium balance in dialysis lowers the dialysate calcium concentrations (pro part)

Prior to the advent of calcitriol therapy, haemodialysis (HD) patients were often in negative calcium (Ca) balance between dialyses because of severely impaired Ca absorption [1] that led to the recommendation of dialysate inlet Ca concentration (CdiCa++) 3.0–3.5 mEq/L, higher than plasma concentration [2]. Over the past 25 years since the advent of calcitriol, virtually all haemodialysis patients absorbed a substantial portion of dietary and phosphate binder calcium ingested between dialyses and yet CdiCa++ 3.0 mEq/L has continued to be widely used. The total Ca absorbed between dialyses (CaAbsT) must be removed by the dialyser (JdCaT) to achieve net zero Ca mass balance over the dialysis cycle and prevent chronic Ca overload that likely contributes to the high rate of vascular calcification in haemodialysis patients [3–5]. From this perspective, it follows that the CdiCa++ prescribed should result in neutral Ca mass balance and thus total Ca removed during dialysis (JdCa++), the sum of diffusive (JDiffCa++) and convective Ca++ (JConvCa++) removal, should equal CaAbs in accordance with