Investigation of association between serum C-reactive protein concentrations and proteinuria in dogs.

OBJECTIVES: Identify if serum C-reactive protein concentrations and specific diseases are associated with proteinuria (defined as urine protein:creatinine ratio >0.2) in dogs without known pathological pre-renal, renal or post-renal causes. MATERIALS AND METHODS: Hypothesis generating retrospective study. Dogs with contemporaneous urine protein:creatinine ratio and serum C-reactive protein concentrations and without known causes of pathological pre-renal, renal or post-renal causes of proteinuria were included. Continuous and categorical variables were compared between groups using non-parametric statistics, and multivariable logistic regression analyses evaluated associations between specific diseases or selected clinicopathological variables (including serum C-reactive protein concentrations) and proteinuria. RESULTS: Seventy-one overtly proteinuric (urine protein:creatinine ratio >0.5), 74 borderline proteinuric (urine protein:creatinine ratio 0.21 to 0.5) and 234 non-proteinuric dogs (urine protein:creatinine ratio ≤.2) were included. Proteinuria (urine protein:creatinine ratio >0.2) was less prevalent in dogs diagnosed with chronic enteropathy (11% [4/35] vs. 41% [141/344]; P < .001) compared to the rest of the population. Proteinuria was more prevalent in dogs with chronic hepatitis (71% [10/14] vs. 37% [135/365]) and tended to be more prevalent in dogs with pancreatitis (57% [12/21] vs. 37% [133/358]; P = .103) compared to the rest of the population. On multivariable analysis, serum C-reactive protein concentration was independently associated with increased odds of proteinuria (OR = 1.031 [95% CI: 1.012 to 1.051]; P = .001) and a diagnosis of chronic enteropathy was independently associated with decreased odds of proteinuria (OR = 0.21 [95% CI: 0.064 to 0.681]; P = .009). CLINICAL SIGNIFICANCE: Systemic inflammation might be associated with proteinuria in dogs, although further investigations to evaluate if proteinuria resolves following the resolution of these conditions are required to confirm any causal association.