[Postoperative acute kidney injury: confounder or causal link for surgical outcome?]

Demographic change and increase of complexity of diagnostic and surgical procedures lead to an increasing relevance of acute kidney injury as postoperative complication. Postoperative acute kidney injury is associated with higher mortality, morbidity and treatment costs. It has not yet been unequivocally proven that postoperative acute kidney injury is in fact causally linked with worse treatment outcome in surgical patients. This article aims to give an overview of the phenomenon postoperative acute kidney injury, to discuss problems of demonstrating causal relations in biomedical research, and to present arguments for and against the hypothesis that postoperative acute kidney injury is causally linked to worse surgical outcome.