Cardiorenal syndrome (CRS) is an umbrella term used in the medical field that defines disorders of the heart and kidneys whereby "acute or chronic dysfunction in one organ may induce acute or chronic dysfunction of the other".[1] When one of these organs fails, the other may subsequently fail.[2] The heart and the kidneys are involved in maintaining hemodynamic stability and organ perfusion through an intricate network. Patients who have renal failure first may be hard to determine if heart failure is concurrent.[3] These two organs communicate with one another through a variety of pathways in an interdependent relationship. In a 2004 report from the National Heart, Lung and Blood Institute, CRS was defined as a condition where treatment of congestive heart failure is limited by decline in kidney function.[4] This definition has since been challenged repeatedly but there still remains little consensus over a universally accepted definition for CRS. At a consensus conference of the Acute Dialysis Quality Initiative (ADQI), the CRS was classified into five subtypes primarily based upon the organ that initiated the insult as well as the acuity of disease.[5]

Reference
Wiki: Cardiorenal syndrome type 4