Quantitative Assessment of Urea Generation and Elimination in Healthy Dogs and in Dogs with Chronic Kidney Disease

摘要

Background: Kinetic assessment of urea, the main end product of protein metabolism, could serve to assess protein catabolism in dogs with chronic kidney disease (CKD). Protein malnutrition and catabolism are poorly documented in CKD and they often are neglected clinically because of a lack of appropriate evaluation tools.Hypothesis: Generation and excretion of urea are altered in dogs with CKD.Animals: Nine dogs with spontaneous CKD (IRIS stages 2–4) and 5 healthy research dogs.Methods: Endogenous renal clearance (Cl_renal) of urea and creatinine was measured first. Exogenous plasma clearance (Cl_plasma, total body clearance) of the 2 markers then was determined by an IV infusion of urea (250–1,000 mg/kg over 20 minutes) and an IV bolus of creatinine (40 mg/kg). Extrarenal clearance (Cl_extra) was defined as the difference between Cl_plasma and Cl_renal. Endogenous urea generation was computed assuming steady-state conditions.Results: Median Cl_renal and Cl_extra of urea were 2.17 and 0.21 mL/min/kg in healthy dogs and 0.37 and 0.28 mL/min/kg in CKD dogs. The proportion of urea cleared by extrarenal route was markedly higher in dogs with glomerular filtration rate extra remained plasma.Conclusion: Extrarenal pathways of urea excretion are predominant in dogs with advanced CKD and justify exploring adjunctive therapies based on enteric nitrogen excretion in dogs. A trend toward increased urea generation may indicate increased catabolism in advanced CKD.