Measurement of urinary urea nitrogen content as an estimate of the amount of total urinary nitrogen loss in dogs in intensive care units

Abstract

Objective To investigate whether urinary urea nitrogen (UUN) content can be used to accurately estimate total urinary nitrogen content in hospitalized dogs. Design Prospective, cohort study. Animals 24 client-owned dogs admitted to an intensive care unit of a veterinary teaching hospital. Procedure Indwelling urinary catheters and closed collection systems were placed for the purpose of monitoring urine output. Urine was collected during a 24-hour period from each dog. For each collection, the total volume was measured. Urine was analyzed for urea nitrogen content at an in-house laboratory, using standard methods for determination of BUN content. Total urinary nitrogen content was determined by another laboratory, using Kjeldahl's method. Correlation between UUN content and total urinary nitrogen content was evaluated by use of linear regression analysis. Results Total urinary nitrogen content adjusted for metabolic body weight ranged from 0.21 to 2.21 g/ kg0.75/d (mean ± SD, 0.81 ± 0.46 g/kg0.75/d). Adjusted UUN content ranged from 0.05 to 1.50 g/kg0.75/d (0.54 ± 0.38 g/kg0.75/d). Total urinary nitrogen content was highly correlated with UUN content (R2, 0.88; P < 0.001). Clinical Implications Measurement of UUN content can be used to estimate total urinary nitrogen content in a clinical setting. Furthermore, critical illness in dogs is associated with substantial catabolism of endogenous proteins. (J Am Vet Med Assoc 1997; 210:356–359