Cardiorenal syndrome.

Very often, physicians confront with patients who have concomitant heart and kidney failure. The coexistence of kidney and heart failure carries an extremely bad prognosis. The exact cause of deterioration of kidney function and the mechanism underlying this interaction are complex, multifactorial in nature, and still not completely understood. Both the heart and the kidney act in tandem to regulate blood pressure, vascular tone, diuresis, natriuresis, etc. An extension to the Guytonian model of volume and blood pressure control is proposed called cardiorenal connection. Regulating actions of Guyton's model were coupled to their extended actions on structure and function of the heart and the kidney changes in the rennin-angiotensin-aldosterone system, the imbalance between nitric oxide and reactive oxygen species, the sympathetic nervous system, and inflammation are the cardiorenal connectors to develop cardiorenal syndrome. Imbalance in this closed complex will often lead to deterioration of both cardiac and kidney function. The World Congress of Nephrology emphasized vast interrelated derangements that can occur in cardiorenal syndrome and proposed that the recent definition of cardiorenal syndrome be modified into categories whose labels reflect the likely primary and secondary pathology and time frame. For management, drugs that impair kidney function are undesirable, particularly in a population with already compromised or at risk of kidney function. In severe volume-loaded patients who are refractory to diuretics, management of cardiorenal dysfunction is challenging. In the absence of definitive clinical trials, treatment decision must be based on a combination of patient's condition and understanding of individual treatment options.