[The relationship between the heart and the kidney in acute heart failure: doubts of the cardiologist and the nephrologist's point of view].

The pathophysiological interactions that link the heart and kidney in heart failure are multiple and complex. This issue constitutes one of the most vexing and difficult challenges facing cardiologists. In the setting of acute decompensated heart failure, worsening renal function has traditionally been directly associated with poor clinical prognosis and complicates treatment. In the last years, many reports suggest that worsening renal failure may represent the final common pathway of several mechanistically distinct processes, with different prognostic implications. In the clinical scenario, the clinical significance of transient worsening of renal function may be different as compared with irreversible or progressive renal failure. In addition, it can represent a relatively normal response to treatment-induced physiological derangements such as a reduction in renal perfusion and/or intravascular volume. We here focus on these highlights, with special reference to the diagnostic criteria of renal dysfunction and the management of fluid overload. Two expert nephrologists were asked to answer a few important clinical questions: how should renal dysfunction be recognized and monitored? Are there therapies to counteract it and when, and more importantly, for whom should be applied? Their answers serve as touchstones for cardiologists to provide better individualized care for their patients with acute heart failure. Only a multidisciplinary and collaborative management of cardio-renal interactions will help to mitigate the difficult day-to-day clinical practice and improve our understanding of this condition through a concerted and constructive approach.