Cardiorenal Syndrome: An Updated Classification Based on Clinical Hallmarks

Cardiorenal syndrome (CRS) is defined as progressive, combined cardiac and renal dysfunction. In this mini review, a historical note on CRS is presented, the pathomechanisms and clinical hallmarks of both chronic heart failure and chronic kidney disease are discussed, and an updated classification of CRS is proposed. The current consensus classification relies on the assumed etiology and the course of the disease, i.e., acute or chronic CRS. Five types are described: type-I CRS presenting as acute cardiac failure leading to acute renal failure; type-II CRS presenting as chronic cardiac failure leading to chronic renal failure; type-III CRS presenting as acute kidney injury aggravating heart failure; type-IV CRS presenting as chronic kidney failure aggravating heart failure; and type-V CRS presenting as concurrent, chronic cardiac and renal failure. For an updated classification, information on the presence or absence of valvular heart disease and on the presence of hyper- or hypovolemia is added. Thus, CRS is specified as acute (type-I, type-III or type-V CRS) or chronic (type-II, type-IV or type-V) CRS, as valvular or nonvalvular CRS, and as hyper- or hypovolemia-associated CRS if euvolemia is absent. To enable the use of this updated classification, validation studies are mandated.

Automated summary

Cardiorenal syndrome (CRS) refers to progressive dysfunction of both the heart and the kidney. This mini review discusses the pathomechanisms and clinical hallmarks of chronic heart failure and chronic kidney disease, and proposes an updated classification for CRS. This classification takes into account the etiology, course of the disease, presence of valvular heart disease, and volume status.