About Kidney Transplant
Among patients with ESRD, loss of renal function is often accompanied by disturbances in mineral metabolism, including decreased levels of serum calcium and elevated serum phosphorus, in addition to increased parathyroid hormone (PTH) resulting from secondary hyperparathyroidism. In several observational studies, biochemical parameters have been reported to be associated with poor clinical outcomes, such as mortality and cardiovascular disease (CVD), among patients with ESRD requiring dialysis. In a systematic review published in 2011, Palmer et al. identified 47 cohort studies and described a linear relationship between high serum phosphorus and all-cause mortality in individuals with CKD. In contrast, some studies have demonstrated U-shape or J-shape (nonlinear) associations between serum phosphorus levels and mortality risk in patients with CKD. A number of recent studies have indicated that serum phosphorus levels are independently associated with CKD progression and kidney failure in nondialysis-dependent patients with CKD. Even in individuals with normal renal function, there is evidence that higher serum phosphorus levels are associated with an increased risk of CVD and mortality.
Hypophosphatemia and renal phosphorus wasting are common during several months after renal transplantation, and are associated with inappropriately high PTH and fibroblast growth factor-23 (FGF-23) levels. Renal phosphorus wasting is known to regress by 1 year after successful kidney transplantation. In addition, hyperphosphatemia or hypophosphatemia often persist at 1 year after renal transplantation as the result of deterioration of allograft function, or persistent hyper- or hypoparathyroidism. Studies concerned with the effect of hyper- or hypophosphatemia on graft and patient survival in kidney transplant recipients (KTRs) are scarce. Thus, this multicenter cohort study aimed to evaluate the relationship between post-transplant serum phosphorus levels and graft failure or patient mortality in KTRs.
This study selected a total of 2786 KTRs with recorded serum phosphorus levels at 1 year after renal transplantation from Seoul National University Hospital, Boramae Medical Center, and Asan Medical Center, between January of 1997 and August of 2012. A total of 176 pediatric renal transplant patients and 111 patients with mortality or graft failure at <1 year after transplantation were excluded. Demographic and laboratory data were retrospectively reviewed from medical records. We obtained the laboratory data at 1 year after transplantation, because parameters of mineral metabolism are known to stabilize by 1 year after transplantation. The serum calcium level was adjusted for serum albumin, according to the following equation: corrected calcium = measured calcium + 0.8 × (4.0 − serum albumin in grams per deciliter). The serum phosphorus level was measured by reaction of inorganic phosphorus with ammonium molybdate under acidic conditions to produce the phosphomolybdate complex, which was quantified by spectrophotometry. The eGFR was calculated by the Modification of Diet in Renal Disease equation.
Journal of Nephrology and Urology is an Open Access peer-reviewed publication that discusses current research and advancements in diagnosis and management of kidney disorders as well as related epidemiology, pathophysiology and molecular genetics.
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Journal of Nephrology and Urology