Longitudinal Effects of Renal Diet Initiation on Serum Calcium and CKD Progression in Cats

Abstract:

Introduction: Use of renal diets in IRIS stage 1 chronic kidney disease (CKD) has been controversial. Studies have shown improved outcomes but there is concern around increased total calcium (tCa) in some cats on phosphate-restricted diets.

Objective: To compare longitudinal serum tCa trends in cats with IRIS Stage 1 or 2 CKD that initiated a renal diet with those that did not and evaluate disease progression. Animals: Medical records from 1,401 cats diagnosed with CKD by veterinarians in North America were retrospectively analyzed.

Methods: Cats with IRIS Stage 1 or 2 CKD were randomly selected from a retrospective commercial veterinary database. A previous publication demonstrated delayed progression and improved survival with renal diets in this cohort. Serum calcium trajectories were evaluated using a nonlinear mixed effects model with random intercepts. Model-based contrasts assessed differences in slopes and tCa across predefined intervals. CKD progression to a later IRIS stage was assessed using a continuous time multistate model.

Results: Following renal diet initiation, tCa increased significantly compared with untreated cats (mean difference: 0.3357 mg/dL; P < 0.001). tCa was not associated with time spent in CKD stages before progression (Stage 1: P = 0.863, Stage 2: P = 0.400). Conclusions and Clinical Importance: Renal diet initiation in this population of cats diagnosed with CKD in IRIS Stage 1 and 2 improved survival and delayed progression but also is associated with increased tCa. Interestingly, tCa did not negatively impact disease progression in the first 3 years after diagnosis.