Kidney Week

Abstract: TH-PO146

Phosphate Loading per Nephron Predicts CKD Progression and All-Cause Death in Patients with Nondialysis-Dependent CKD: The Fukuoka Kidney Disease Registry (FKR) Study

Session Information

• CKD-MBD: Clinical
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Bone and Mineral Metabolism

• 502 Bone and Mineral Metabolism: Clinical

Authors

• Yamada, Shunsuke, Kyushu University, Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Fukuoka, Japan

Shunsuke Yamada, MD, PhD

• Tanaka, Shigeru, Fukuoka Dental College, Department of Medicine, Fukuouka, Japan

Shigeru Tanaka, MD, PhD

• Tsuruya, Kazuhiko, Nara Medical University, Department of Nephrology, Nara, Japan

Kazuhiko Tsuruya, MD, PhD

• Kitazono, Takanari, Kyushu University, Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Fukuoka, Japan

Takanari Kitazono, MD, PhD

• Nakano, Toshiaki, Kyushu University, Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Fukuoka, Japan

Toshiaki Nakano, MD, PhD

Background

CKD-MBD develops in the early stages of CKD and contributes to the increased risk of end-stage kidney disease and death. Thus, it is critical to identify new indicators that reflect early events of CKD-MBD and initiate appropriate interventions in the non-dialysis CKD population.

Methods

We examined 3,320 patients enrolled in the FKR study, a prospective observational study of patients with non-dialysis CKD stages G1–G5. We focused on the urinary phosphate excretion per nephron as an indicator of early CKD-MBD pathogenesis. Urinary phosphate excretion per nephron was determined by using the estimated urinary phosphate excretion divided by eGFR as a proxy for nephron number. Estimated phosphate excretion was calculated using estimated 24-hour creatinine (Cr) excretion and urinary Cr and phosphate concentrations. After patients were divided into quartiles(Q1-Q4) according to the baseline urinary phosphate loading per nephron, we determined the association of phosphate loading per nephron with the risk of all-cause death and composite kidney event using longitudinal data. The composite kidney event was defined as the development of end-stage kidney failure and/or a 1.5-fold increase in serum creatinine concentrations.

Results

Over 5 years, 1,132 patients developed a composite kidney event, and 295 died. Urinary phosphate loading per nephron elevated as early as an eGFR of 70 mL/min/1.73m² and preceded the changes in serum PTH, calcium, and phosphorus concentrations. Multivariate-adjusted Cox proportional hazard regression analyses revealed a significant association between an increased phosphate loading per nephron and a heightened risk of developing a composite renal event and all-cause death. The hazard ratios (95%CI) for all-cause death and composite kidney events in Q4 were significantly higher than those in Q1: 1.70 (1.01-2.85) and 1.57 (1.16-2.10), respectively. These associations were independent of the serum PTH, calcium, and phosphorus concentrations.

Conclusion

Phosphate loading per nephron may reflect the early stage of CKD-MBD pathophysiology and predict CKD progression and all-cause death in patients with non-dialysis CKD. Early intervention for phosphate overload may retard the progression of CKD and decrease the death risk in this population.