Assessment of serum symmetric dimethylarginine and creatinine concentrations in cats with urethral obstruction

Objectives The aims of this study were to evaluate serum symmetric dimethylarginine (SDMA) and creatinine concentrations in cats with urethral obstruction pre- and post-decompression of the obstruction, and to determine if pre-decompression values were predictive of post-decompression renal function, as measured by SDMA and creatinine. Methods This was a prospective observational study. Twenty-five client-owned cats with urethral obstruction were hospitalized for decompression of the obstruction. Serum SDMA and creatinine were prospectively assessed at presentation, 24 h post-decompression and 5-20 days post-decompression. Urinalysis and culture were assessed at presentation and at the final follow-up. Exclusion criteria included positive urine culture, reobstruction or failure to obtain required samples. Results Mean SDMA concentration dropped by 41.8% from an initial pre-decompression concentration of 17.6 mu g/dl to 10.3 mu g/dl 24 h post-decompression (P <0.001). The mean creatinine value dropped by 38.4% from an initial pre-decompression concentration of 2.5 mg/dl to 1.5 mg/dl 24 h post-decompression (P <0.001). There was no association between SDMA concentration at initial presentation and SDMA concentration 5-20 days after urethral catheterization (Spearman's rho = 0.205, P = 0.314). Creatinine concentration upon initial presentation was associated with the 5-20 day values after urethral catheterization (Spearman's rho = 0.583, P <0.002). Twenty percent of cases were excluded due to bacterial growth on initial urine culture. SDMA and creatinine concentrations were significantly higher in these cases (median 59 mu g/dl and 10.9 mg/dl, respectively) compared with those with negative cultures (median 14 mu g/dl and 1.6 mg/dl [P P <0.001], respectively). Conclusions and relevance Both SDMA and creatinine decreased significantly after urethral catheterization, suggesting that renal function post-decompression cannot be predicted by the pre-decompression concentrations of these values.