Acute lung injury/acute respiratory distress syndrome (ARDS) may be induced by a variety of disease entities. Apart from supportive treatment including lung protective ventilation, identification of the underlying process is of crucial importance for optimal therapeutic results. Usually the cause of ARDS can be identified by history, laboratory and radiologicial tests. In some cases a diagnosis cannot be made in spite of an extensive, less invasive diagnostic work-up. In these situations the risks of empirical treatment have to be balanced against the procedural risk of invasive diagnostics, namely open lung biopsy. Today, reports on more than 500 lung biopsies performed in selected ARDS patients are available showing a relevant diagnostic yield at an acceptable procedure-associated risk. Intensive care physicians should be aware of this diagnostic instrument, which can represent the decisive diagnostic step in patients with ARDS of unknown origin.
