Serum fibroblast growth factor-23 and magnesium concentrations in cats with acute kidney injury: association with disease pathophysiology.

Cats with acute kidney injury (AKI) have a high mortality rate and are at risk of progression to chronic kidney disease (CKD). Fibroblast growth factor-23 (FGF-23) and magnesium, which are involved in mineral homeostasis and AKI outcomes, may contribute to this progression. This study aimed to evaluate serum FGF-23 and magnesium concentrations at diagnosis in cats with AKI and to investigate their associations with clinical outcomes. This retrospective study included client-owned cats with AKI. Serum FGF-23 and magnesium concentrations were measured at diagnosis, and their associations with AKI outcomes were analyzed. Forty-five cats were enrolled. Serum FGF-23 (P=0.01) and magnesium (P=0.01) concentrations were elevated. Serum FGF-23 tended to increase with prior CKD severity, although differences among CKD groups were not significant (P=0.10). Serum FGF-23 was significantly associated with treatment duration (P=0.008) and changes in serum creatinine during hospitalization (P=0.003), independent of prior CKD status and serum creatinine at diagnosis. A 10-fold increase in FGF-23 was associated with an approximately 47% decrease in the hazard of reaching the lowest serum creatinine concentration. Magnesium was not significantly associated with these outcomes. Measurement of serum FGF-23 at the time of AKI diagnosis may help predict hospitalization duration and renal function decline. Although the role of serum magnesium in the pathophysiology of AKI could not be clearly determined, further investigation of its relationship with FGF-23 may contribute to the development of novel therapeutic strategies.