Symmetric dimethylarginine (SDMA) has been proposed as a sensitive and specific renal biomarker whose concentration increases earlier than serum creatinine (SCr) as glomerular filtration rate decreases. SDMA is a promising parameter in the diagnosis and management of chronic kidney disease (CKD), and it is included into the International Renal Interest Society (IRIS) guidelines.

The aim of the study is to assess the usefulness of a single determination of SDMA in the evaluation of renal status in dogs at risk or affected with CKD, and to evaluate its correlation with SCr and other parameters of renal function.

Ninety-five dogs were consecutively selected within the patients referred to the University Veterinary Hospital of Milan. On the first clinical examination, all these dogs underwent physical examination, haematology and blood chemistry (including serum SDMA and SCr). Urinalysis and urinary protein:creatinine ratio (UPC) were performed in 89 cases while ultrasound examination was done in 60 dogs. All the dogs were staged according to the IRIS guidelines. Statistical analysis was performed by JMP 7 software (SAS Institute Inc., Cary, USA).

SDMA showed, as expected, a significant correlation with SCr, urine specific gravity (USG) and UPC ratio (p<0,05). IRIS staging, according to SCr, resulted as follows: 26 (27,4%) dogs were included in stage 0, 39 (41%) in stage 1, 12 (12,6%) in stage 2, 17 (17,9%) in stage 3 and 1 (1,1%) in stage 4. SDMA evaluation modified IRIS staging in 12 (12,6%) dogs. SDMA was increased in 51 (53,7%) dogs; in 8 (15,7%) of these, SDMA was equal to the cut-off value (14 µg/dL). In 29 (56,9%) of the "high SDMA" cases, SCr was >1,4 mg/dL, while in the other 22 (43,1%) there were already one or more alterations: decrease of USG in 14 (63,6% of 22) cases, increase of UPC ratio in 15 (68,2%) cases, ultrasound features suggestive of CKD in 9 (40,1%) cases. SDMA was the only altered parameter in 4 (4,2%) dogs. SDMA was normal and creatinine slightly increased in 1 (1,1%) dog.

SDMA is a useful and reliable parameter for the diagnosis and management of CKD, but the evaluation of other markers of renal function and diagnostic imaging are essential in order to correctly approach the patient from the diagnostic and therapeutic point of view, especially at the first clinical presentation. Furthermore, patients with normal SCr and altered SDMA require further evaluations to confirm the development of CKD.

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