The Relationship between Serum Calcium Concentration and Outcome in Horses with Renal Failure Presented to Referral Hospitals

Background: Hypercalcemia is common in horses with renal failure, but it is not known whether it impacts prognosis. Hypothesis/Objectives: The primary objective of this study was to determine whether hypercalcemia was associated with decreased likelihood of survival to discharge in horses with renal failure. Secondary objectives were to determine whether hypercalcemia was more common in acute (ARF) or chronic renal failure (CRF), whether feeding alfalfa was associated with hypercalcemia, and whether serum creatinine concentration was associated with survival. Animals: Medical records of 63 horses presented to referral hospitals for renal failure were evaluated. Cases were classified as ARF or CRF based on historical and clinical findings. Methods: The distribution of hypocalcemic, normocalcemic, and hypercalcemic cases in the ARF and CRF groups was determined. Mean serum calcium and creatinine concentrations for survivors and nonsurvivors, and for ARF and CRF cases, were compared. Mean serum calcium concentrations for cases fed alfalfa or not fed alfalfa were compared. Results: Hypercalcemia was significantly more common in CRF than ARF cases. CRF cases fed alfalfa were significantly more likely to be hypercalcemic. There was no significant difference in serum calcium concentration between survivors and nonsurvivors. Serum creatinine concentration was significantly higher in nonsurvivors and in ARF cases. Conclusions and Clinical Importance: Horses with CRF are more likely to be hypercalcemic than horses with ARF. Hypercalcemia was not associated with outcome in renal failure cases in this study. Additional research on the impact of dietary calcium on long-term well-being in horses with CRF is warranted.