To review the definition and causes of acute respiratory distress syndrome (ARDS).To show the pathological stages of this nonspecific inflammatory condition of the lung.To illustrate the radiological findings (both on X-ray and CT) of the different phases of the disease. To identify and recognize possible complications related to ARDS with the different imaging tests.To provide the most relevant differential diagnosis.To review the management and prognosis of patients with ARDS in the ICU.

A. ARDS:- Definition (criteria).- Causes and clinical disorders associated with ARDS: direct and indirect lung injury. B. Pathophysiology.- Stages of the disease (exudative, inflammatory and fibroproliferative phases).C. Correlation of imaging findings with pathological stage of the disease.- Exudative or acute phase (1-7 days): anteroposterior density gradient.- Proliferative or intermediate phase (8-14 days): patchy airspace and reticular opacities; thickening of the alveolar septa; bronchiectasis and honeycombing, as signs of poor prognosis.- Fibrotic phase (>15 days): Thick reticular pattern and ground-glass opacifications in the anterior region of the lung; pulmonary cysts and bullae.- Resolution phaseD. Complications:- Barotrauma: pneumomediastinum and pneumothorax- Pneumonia and abscesses.?. Differential diagnosis: cardiogenic edema, diffuse hemorrhage and acute interstitial pneumonia.F. Management and prognosis.