Table 1. Cardiorenal syndrome classification system by Ronco et al.

CRS General Definition:

A complex pathophysiologic disorder of the heart and kidneys whereby acute or chronic dysfunction in 1 organ may induce acute or chronic dysfunction in the other organ.

Types of CRS

CRS Type 1 (acute CRS)

Description: Abrupt worsening of cardiac function leading to AKI

Examples: Acute coronary syndrome, acute decompensated heart failure

CRS Type 2 (chronic CRS)

Description: Chronic abnormalities in cardiac function causing progressive and permanent CKD

Examples: Chronic heart failure, ischemic heart disease, hypertension

CRS Type 3 (acute renocardiac syndrome)

Description: Abrupt worsening of kidney function causing acute cardiac disorder

Examples: Postsurgery AKI, acute glomerulonephritis, rhabdomyolysis

CRS Type 4 (chronic renocardiac syndrome)

Description: CKD contributing to decreased cardiac function, cardiac hypertrophy, fibrosis, and/or increased risk for adverse cardiovascular events

Examples: Cardiac hypertrophy/fibrosis in CKD

CRS Type 5 (secondary CRS)

Description: Systemic condition causing both acute cardiac and kidney injury and dysfunction

Examples: sepsis, diabetes mellitus

Abbreviations: AKI: acute kidney injury; CKD: chronic kidney disease; CRS: cardiorenal syndrome.