Cardiorenal syndrome

In medicine, the cardiorenal syndrome (CRS) is a condition characterized by kidney failure and heart failure. The primarily failing organ may be either the heart or the kidney, and it is often this failing organ that precipitates failure of the other.

Classification
The cardiorenal syndrome is divided by Ronco et al. into five subtypes:
 * Type 1
 * In type 1 (acute) CRS, acute decompensated heart failure leads to acute kidney injury.


 * Type 2
 * Type 2 (chronic) CRS is characterized by chronic heart failure that leads to chronic kidney disease.


 * Type 3
 * Also called the acute renocardiac syndrome, type 3 CRS is due to acute kidney injury that leads to acute cardiac dysfunction such as arrhythmia or heart failure.


 * Type 4
 * Type 4 CRS, or chronic renocardiac syndrome, is characterized by primary chronic kidney disease that contributes to cardiac dysfunction.


 * Type 5
 * Also called secondary CRS, the fifth type of CRS is combined heart and kidney dysfunction due to systemic disorders such as sepsis and systemic lupus erythematosis.

The distinction between CRS type 2 and CRS type 4 is based on the assumption that, also in advanced and chronic disease, two different pathophysiological mechanisms can be distinguished, whereas both CKD and HF often develop due to a common pathophysiological background, most notably hypertension and diabetes. Furthermore, the feasibility of the distinction between CRS type 2 and 4 in terms of diagnosis can be questioned.

Others view the Cardiorenal Syndrome in a more holistic, integrative manner. They defined the Cardiorenal Syndrome as a pathophysiological condition in which combined cardiac and renal dysfunction amplifies progression of failure of the individual organ, by inducing similar pathophysiological mechanisms. Therefore, regardless of which organ fails first, the same neurohormonal systems are activated causing accelerated cardiovascular disease, and progression of damage and failure of both organs.

The NHLBI Working Group on Cardio-Renal Connections in Heart Failure and Cardiovascular Disease has defined the "cardio-renal syndrome" as a syndrome "in which therapy to relieve congestive symptoms of heart failure is limited by further decline in renal function. It is clear that our current understanding of cardio-renal connections is inadequate to explain many of the clinical observations in heart failure or to direct its therapy."