Evaluation of the diagnostic value of the renal resistive index as a marker of the subclinical development of cardiorenal syndrome in MMVD dogs

Myxomatous mitral valve disease (MMVD) in dogs inevitably causes renal dysfunction. These interactions are known as the cardiorenal syndrome (CRS). The main aims of the study were to evaluate whether renal resistive index (RRI) may be useful as a non-invasive marker in subclinical stage of kidney injury in dogs with MMVD and to compare RRI with SDMA and Cyst C.Methods: Forty-four dogs were divided into two groups: control—15 healthy dogs and the heart group—29 dogs with MMVD (ACVIM class Cc). Study protocol included: anamnesis, clinical examination, electrocardiography, echocardiography, chest radiography, abdominal ultrasonography with measurements of the renal resistive index (RRI), urine, and blood analysis.Results: The RRI in the heart group was significantly higher 0.725 ± 0.035 versus control group 0.665 ± 0.028 ( p < 0.00085). The RRI cut-off point in dogs with stable chronic heart failure (CHF) under 8 years is 0.775, in older 0.64. RRI was similar in MMVD dogs treated with ACE-I + furosemide and dogs treated ACE-I + torasemide + pimobendan + spironolactone. There was no correlation between RRI and SDMA or Cyst C.Conclusion: RRI is more sensitive than creatinine, SDMA and Cyst C to reveal kidney injury in MMVD dogs class Cc younger than 8 years.