Research Communications of the 27(th) ECVIM-CA Congress: Intercontinental, Saint Julian's, Malta, 14th to 16th September 2017

Disclosures: No disclosures to report. Increased glomerular filtration rate (GFR) and decreased muscle mass make identification of chronic kidney disease (CKD) in hyperthyroid cats challenging. Symmetric dimethylarginine (SDMA) is a promising indirect renal biomarker that correlates closely with GFR in healthy geriatric and CKD cats. The aim of this study was to evaluate SDMA reliability as a renal biomarker in hyperthyroid cats. Forty-seven client-owned hyperthyroid nonazotemic (creatinine <168 lmol/L) cats were prospectively enrolled and treated with radioiodine ( 131 I). Antithyroid medication was discontinued 10 days prior to 131 I treatment. Cats had to be free of any other medication at least for 14 days prior to 131 I treatment and free of any other clinically relevant systemic disease. Creatinine and SDMA (IDEXX SDMA TM Test) were determined before (T0) and 1 month after (T1) treatment. GFR (plasma exogenous creatinine clearance test) was measured at T0 and T1 in 10 of 47 cats. As expected, creatinine significantly increased (P < 0.001) and GFR significantly decreased (P < 0.001) after 131 I treatment. SDMA did not significantly change over time (P = 0.37). Only 1 cat became azotemic (creatinine >168 lmol/L) at T1 while having normal SDMA at both time points. SDMA was elevated (>14 lg/dL) in 6 of 47 cats at T0 and normalized after treatment in 4 cats. GFR was available in 1 of these 6 cats and was within normal limits (SDMA normalized at T1). SDMA at T1 was increased above 14 lg/dL in 1 cat with borderline low GFR which was defined as GFR <1.9 ml/min/kg. Pearson correlation (n = 10) between GFR and SDMA was moderate to low (r = À0.48, P = 0.16 at T0 and r = À0.36, P = 0.31 at T1) and correlation between GFR and creatinine was moderate (r = À0.54, P = 0.11 at T0 and r = À0.51, P = 0.13 at T1). Forty of forty-one cats with pre-treatment SDMA within reference interval remained non-azotemic post-treatment. However, not enough patients became azotemic post-treatment to evaluate if SDMA can predict post-treatment renal azotemia. Previous studies showed that SDMA is a promising renal biomarker but further studies are necessary to more fully assess its utility in feline hyperthyroidism.