Ionized Hypercalcemia Resolves with Nutritional Modification in Cats with Idiopathic Hypercalcemia and Chronic Kidney Disease

Abstract: Background: Idiopathic hypercalcemia (IHC) and chronic kidney disease (CKD) are two common causes of ionized hypercalcemia in cats. Various nutritional management strategies to address hypercalcemia have been described with little consensus about best practice.
Hypothesis: Feeding a diet with < 200 mg calcium per 100 kilocalories (kcal) and a dietary calcium:phosphorus (Ca:P) ratio < 1.4:1 can effectively manage hypercalcemia in cats.
Animals: Cats with persistent ionized hypercalcemia diagnosed with either IHC (n=7) or CKD (n=2) were included.
Methods: Retrospective case series of cats with ionized hypercalcemia. Cats with neoplasia, primary hyperparathyroidism, or those receiving medications known to affect calcium concentrations (e.g., alendronate, corticosteroids, furosemide) were excluded. Cats were included if nutritional recommendations to address the hypercalcemia were provided and if follow-up ionized calcium (iCa) concentrations were obtained.
Results: Baseline iCa median (range) was 1.56 mmol/L (1.50-1.65 mmol/L). At initial evaluation, 5 cats were fed a diet with > 200 mg calcium/100 kcal, 3 cats were fed a diet with a Ca:P ratio > 1.4:1, and one cat was fed a diet with both > 200 mg calcium/100 kcal and a Ca:P ratio > 1.4:1 (Table 1). Median (range) time from baseline to first recheck of iCa was 10.6 weeks (range, 3.0-20.1 weeks). Ionized hypercalcemia completely resolved in 7/9 cats (78%) and improved in the remaining 2/9 cats (22%). (Figure 1)
Conclusions and clinical importance: Cats with ionized hypercalcemia can return to normocalcemia when fed diets with < 200 mg calcium/100 kcal as well as a dietary Ca:P ratio < 1.4:1.