Acute respiratory distress syndrome (ARDS) is a serious pulmonary reaction with well-defined clinical parameters in humans triggered by many causes besides bacterial and viral pneumonia. However, there is no definitive definition of ARDS parameters in the experimental animal model. With its 2010 workshop report, the American Thoracic Society defined the main histopathological features that determine the presence of ARDS in laboratory animals, such as changes in parenchymal tissue, altered integrity of the alveolar capillary barrier, inflammation, and abnormal lung function. Understanding these parameters, scoring tissue lesions is used to convert observational pathological data into semi-quantitative or quantitative data for statistical analysis and improved precision.