Factors associated with survival in dogs with chronic kidney disease.

Background: Chronic kidney disease (CKD) is associated with morbidity and mortality in dogs. Plasma fibroblast growth factor-23 (FGF-23) concentration is an independent predictor of CKD progression and survival in cats and people with CKD. Objectives: To investigate the relationship among FGF-23, parathyroid hormone (PTH), vitamin D metabolites, and other clinical variables with survival time in dogs with CKD. Animals: Twenty-seven azotemic CKD dogs. Methods: Dogs were recruited prospectively into the study and followed until death or study conclusion. Dogs were International Renal Interest Society (IRIS) staged into stage 2 (n = 9), stage 3 (n = 12), and stage 4 (n = 6) CKD. Survival times were calculated from the date of study inclusion. Univariable Cox regression was used to assess variables associated with survival including body condition score (BCS), muscle condition score, hematocrit, creatinine, CKD stage, serum phosphorus, urine protein:creatinine ratio (UPC), calcium phosphorus product (CaPP), PTH, 25-hydroxyvitamin D, 1,25--dihydroxyvitamin D, and FGF-23 concentrations. Results: Significant hazard ratios (hazard ratio; 95% confidence interval; P value) were as follows: BCS < 4/9 (1.579; 1.003-2.282; P = .05), muscle atrophy (2.334; 1.352-4.030; P = .01), increased creatinine (1.383; 1.16-1.64; .01), hyperphosphatemia (3.20; 1.357-7.548; P = .005), increased UPC (3.191; 1.310-7.773; P = .01), increased CaPP (4.092; 1.771-9.454; P = .003), and increased FGF-23 (2.609; 1.090-6.240; P = .05). Survival times for each IRIS CKD stage were significantly different (P = .01). Conclusions and Clinical Importance: Multiple variables, including FGF-23, were associated with duration of survival in CKD dogs. FGF-23 could be a prognostic marker in dogs with CKD.