Urinary symmetric dimethylarginine: A promising biomarker for acute kidney injury in dogs with pyometra

Abstract Background Symmetric dimethylarginine (SDMA) is a biomarker of renal function derived from arginine methylation, unaffected by muscle mass or diet, and increases after only a 25% reduction in renal function, allowing earlier detection of renal dysfunction compared with serum creatinine. Although serum SDMA is well established in veterinary nephrology, urinary SDMA (uSDMA) remains comparatively underexplored, particularly in dogs with acute kidney injury (AKI). This study evaluated uSDMA concentrations and the uSDMA‐to‐creatinine (uSDMA/Cr) ratio as biomarkers for AKI, using renal histopathology as the reference standard. Methods Twenty‐seven non‐azotemic dogs diagnosed with pyometra were evaluated. uSDMA was measured using ELISA, and renal lesions were histopathologically classified as discrete, moderate or severe. Results Median uSDMA concentrations were significantly higher in dogs with severe lesions (0.43 µg/mL, interquartile range [IQR] 0.40–0.47) compared with those with moderate lesions (0.31 µg/mL, IQR 0.24–0.38) and discrete lesions (0.26 µg/mL, IQR 0.22–0.30) ( p < 0.001). The uSDMA/Cr ratio was lower in the discrete group (0.0031, IQR 0.0026–0.0036) than in the moderate group (0.0039, IQR 0.0032–0.0048) and the severe group (0.0069, IQR 0.0058–0.0080) ( p = 0.0198). Limitations The main limitations include the absence of a healthy control group and lack of serial biomarker measurements, which may restrict the assessment of dynamic changes. Conclusions These preliminary findings suggest that uSDMA and uSDMA/Cr ratio may serve as biomarkers for assessing AKI severity in dogs, supporting earlier detection and monitoring.