Detection of early renal perfusion changes by contrast-enhanced ultrasonography in dogs with preclinical myxomatous mitral valve disease

Since the prognosis of myxomatous mitral valve disease (MMVD) varies, its characterization is clinically relevant, and renal impairment has been identified as one of its associated factors. Intrarenal Doppler ultrasonography (IRD), an intrarenal hemodynamic assessment method, is useful for predicting cardiac- and renal-related death but cannot detect early changes in dogs with preclinical MMVD. Contrast-enhanced ultrasonography (CEUS), another intrarenal hemodynamic assessment method, may identify earlier changes; however, renal perfusion evaluations using CEUS have not yet been performed on dogs with MMVD. We hypothesized that CEUS detects changes earlier than IRD in dogs with preclinical MMVD. This prospective, cross-sectional study examined renal perfusion in dogs without cardiac disease and preclinical MMVD dogs of different American College of Veterinary Internal Medicine stages using CEUS and compared it with IRD indices. Twenty-three dogs with MMVD (ten stage B1 and thirteen stage B2) and 12 control dogs without cardiac disease were included. The rise times of the renal cortex and medulla were measured from a time-intensity curve. The rise time of the cortex was longer in dogs with stage B2 MMVD than in control dogs, while that of the medulla was shortened in the right ventricular dysfunction group in stage B2. No changes were observed in IRD indices (the resistance index and venous impedance index). In conclusion, CEUS detected changes in renal perfusion in dogs with preclinical MMVD even when IRD indices remained unchanged, suggesting the utility of CEUS in evaluations of renal perfusion in MMVD dogs.