Abstract
The association between cardiac and kidney dysfunction has received attention over the past two decades. A putatively unique syndrome, the cardiorenal syndrome, distinguishing five subtypes on the basis of the chronology of cardiac and kidney events, has been widely adopted. This review discusses the methodologic and practical problems inherent to the current classification of cardiorenal syndrome. The term "disorder" is more appropriate than the term "syndrome" to describe concomitant cardiovascular and kidney dysfunction and/or damage. Indeed, the term disorder designates a disruption induced by disease states to the normal function of organs or organ systems. We apply Occam's razor to the chronology-based construct to arrive at a simple definition on the basis of the coexistence of cardiovascular disease and CKD, the chronic cardiovascular-kidney disorder (CCKD). This conceptual framework builds upon the fact that cardiovascular and CKD share common risk factors and pathophysiologic mechanisms. Biological changes set in motion by kidney dysfunction accelerate cardiovascular disease progression and vice versa . Depending on various combinations of risk factors and precipitating conditions, patients with CCKD may present initially with cardiovascular disease or with hallmarks of CKD. Treatment targeting cardiovascular or kidney dysfunction may improve the outcomes of both. The portfolio of interventions targeting the kidney-cardiovascular continuum is in an expanding phase. In the medium term, applying the new omics sciences may unravel new therapeutic targets and further improve the therapy of CCKD. Trials based on cardiovascular and kidney composite end points are an attractive and growing area. Targeting pathways common to cardiovascular and kidney diseases will help prevent the adverse health effects of CCKD.