Effects of Illness on Urinary Catecholamines and their Metabolites in Dogs

Background: Urinary catecholamines and metanephrines have been proposed as a diagnostic tool for identifying canine pheochromocytomas, but the effects of critical illness on urine concentrations of catecholamines and metanephrines currently are unknown. Objectives: To examine the effects of illness on urine concentrations of catecholamines and metanephrines in dogs. Animals: Twenty-five critically ill dogs and 25 healthy age- and sex-matched control dogs. Methods: Prospective observational study. Urine was collected from healthy and critically ill dogs, and urine concentrations of epinephrine, norepinephrine, metanephrine, and normetanephrine were measured by high-performance liquid chromatography with electrochemical detection. Urinary catecholamine and metanephrine : creatinine ratios were calculated and compared between groups. Results: Urinary epinephrine, norepinephrine, metanephrine, and normetanephrine : creatinine ratios were higher in critically ill dogs when compared with a healthy control population (P= .0009, P < 0.0001, P < 0.0001, and P < 0.0001, respectively). Conclusions and Clinical Importance: Illness has a significant impact on urinary catecholamines and their metabolites in dogs. Further investigation of catecholamine and metanephrine concentrations in dogs with pheochromocytomas is warranted to fully evaluate this test as a diagnostic tool; however, the findings of this study suggest that the results may be difficult to interpret in dogs with concurrent illness.