A patient with heart failure and worsening kidney function.

There is high prevalence of CKD, defined by reduced GFR, in patients with heart failure. Reduced kidney function is associated with increased morbidity and mortality in this patient population. The cardiorenal syndrome (CRS) involves a bidirectional relationship between the heart and kidneys whereby dysfunction in either may exacerbate the function of the other, but this syndrome has been difficult to precisely define because it has many complex physiologic, biochemical, and hormonal abnormalities. The pathophysiology of CRS is not completely understood, but potential mechanisms include reduced kidney perfusion due to decreased forward flow, increased right ventricular and venous pressure, and neurohormonal adaptations. Treatment options include inotropic medications; diuretics; ultrafiltration; and medications, such as β-blockers, inhibitors of the renin-angiotensin-aldosterone system, and more novel treatments that focus on unique aspects of the pathophysiology. Recent observational studies suggest that treatments that result in a decrease in venous pressure and lead to hemoconcentration may be associated with improved outcomes. Patients with CRS that is not responsive to medical interventions should be considered for ventricular assist devices, heart transplantation, or combined heart and kidney transplantation.