Clinical utility of estimation of glomerular filtration rate in dogs

BACKGROUND: Glomerular filtration rate (GFR) estimation is the gold standard for assessment of renal function, although the clinical utility of this test is unclear. OBJECTIVES: To describe the clinical utility of GFR estimation in dogs. ANIMALS: Medical records of 132 dogs that had serum iohexol clearance measured between 2012 and 2017. METHODS: Iohexol clearance and clinical records were reviewed and submitting practices contacted to obtain outcome data. Dogs were classified into 4 groups based on the reason for performing GFR estimation: A1 (screening for pre‐azotemic chronic kidney disease [CKD], n = 105), A2 (confirmation of azotemic CKD, n = 3), B (screening for pre‐azotemic acute kidney injury, n = 19), and C (miscellaneous causes, n = 5). Descriptive review of the clinical utility of GFR estimation is provided. RESULTS: For dogs in Group A1, renal disease was diagnosed in 9/9 dogs with a GFR ≥40% decreased below the mean GFR of their body weight category, in 5/6 dogs with a ≥30% but <40% reduction in GFR and in 7/9 dogs with a ≥20% but <30% reduction in GFR. CONCLUSIONS AND CLINICAL IMPORTANCE: Glomerular filtration rate estimation is useful for the diagnosis of CKD before the onset of azotemia.