Cardiorenal syndromes.
The purpose of the present review is to identify the mechanisms involved in the syndrome related to combined heart-kidney dysfunction. The bidirectionality of the syndrome and the various time frames involved in the different clinical pictures have induced to generate a new definition of the cardiorenal syndrome, focusing on five specific subtypes (acute cardiorenal syndrome, type 1; chronic cardiorenal syndrome, type 2; acute renocardiac syndrome, type 3; chronic renocardiac syndrome, type 4; and secondary cardiorenal syndrome, type 5). The new definition allows to characterize the various clinical scenarios and to identify patients with different subtypes in which the primary disorder and the sequelae are clearly described. Biomarkers for early diagnosis of heart and kidney dysfunction may further contribute to a clearer definition of the disorder. The new classification will allow to test diagnostic tools and prevention strategies as well as therapeutic measures that in the past might not have been applied properly due to the lack of a consistent classification of the syndrome.