Acute kidney injury in acute heart failure–when to worry and when not to worry?

Acute kidney injury is common in patients with acute decompensated heart failure. It is more common in patients with acute heart failure who suffer from chronic kidney disease. Worsening renal function is often defined as a rise in serum creatinine of more than 0.3 mg/dL (26.5 µmol/L) which, by definition, is acute kidney injury (AKI) stage 1. Perhaps the term AKI is more appropriate than worsening renal function as it is used universally by nephrologists, internists and other medical practitioners. In health, the heart and the kidney support each other to maintain the body's homeostasis. In disease, the heart and the kidney can adversely affect each other's function, causing further clinical deterioration. In patients presenting with acute heart failure and fluid overload, therapy with diuretics for decongestion often causes a rise in serum creatinine and AKI. However, in the longer term the decongestion improves survival and prevents hospital admissions despite rising serum creatinine and AKI. It is important to realize that renal venous congestion due to increased right-sided heart pressures in acute heart failure is a major cause of kidney dysfunction and hence decongestion therapy improves kidney function in the longer term. This review provides a perspective on the acceptable AKI with decongestion therapy, which is associated with improved survival, as opposed to AKI due to tubular injury related to sepsis or nephrotoxic drugs, which is associated with poor survival.