Mechanisms and mediators of lung injury after acute kidney injury

Acute kidney injury (AKI) is a common complication in hospitalized patients, associated with >50% mortality in those in intensive care who require renal replacement therapy. Data suggest that AKI is a systemic disease that adversely affects the immune system and organ function, and in this way contributes to the high mortality observed in affected patients. Data from patients and animal models indicate that AKI adversely affects the lungs. Respiratory complications are common in patients with AKI and include pulmonary oedema, respiratory failure requiring mechanical ventilation, prolonged duration of mechanical ventilation, and prolonged weaning from mechanical ventilation. The development of respiratory failure in patients with AKI greatly increases the risk of death. Data from animal models support the notion that cardiogenic pulmonary oedema (from volume overload) and non-cardiogenic pulmonary oedema (from endothelial injury due to inflammation and apoptosis) can occur in AKI. In this Review we discuss the clinical, epidemiologic, and animal data that provide insights into the mechanisms by which AKI can lead to lung injury and respiratory complications. Elucidation of the mechanisms of lung injury and respiratory complications after AKI is essential to develop effective therapies and reduce the high mortality associated with AKI and respiratory failure.