Abstract: Abstract: Objective To investigate the characteristics and cytological changes of pleural effusion (PE) before and after drainage in patients with different causes. Methods From April 2016 to December 2017, data of 179 patients with moderate and massive PE were collected from the Pulmonary and Critical Care Medicine of Tianjin Chest Hospital. According to the pathological and physicochemical characteristics of pleural effusion, the patients were divided into tuberculous pleural effusion (TPE) grouop (n=37), malignant effusion (MPE) group (n=87), parapneumonic effusion (PPE) group (n=39) and chronic heart failure caused pleural effusion (CHFPE) group (n=16). The pleural effusion (500-1 000 mL) was drained with a tube through the pleural cavity. Before and after 24 hours of drainage, 4 mL of pleural samples were collected to analyze the changes of albumin, lactic dehydrogenase (LDH), white blood cells, monocytes, multinucleated cells and mesothelial cells. Results The PPE, MPE and TPE groups showed exudate before and after drainage. In CHFPE group, exudate became transudate after drainage in 5 cases (83.33%). Before drainage, the leukocyte counts of pleural fluid were lower in the MPE, PPE, and CHFPE groups than those in the TPE group. After drainage, the leukocyte counts of pleural fluid were still lower in the three groups than those in the TPE group, and the PPE and CHFPE groups were lower than those in the MPE group (P＜0.05). Leukocytes of pleural fluid increased after drainage in the MPE group (P＜0.05). Before drainage, the monocyte counts were lower in the MPE, PPE, and CHFPE groups than those in the TPE group. After drainage, the monocyte counts were still lower in the PPE and CHFPE groups than those in the TPE group, and which was increased after drainage in the MPE group (P＜0.05). There were no significant differences in multinucleated cell counts before and after drainage between the four groups (P＞0.05). Before drainage, the mesothelial cell counts of pleural fluid was higher in the MPE group than those of the other three groups. After drainage, the mesothelial cell count of pleural fluid was still the highest in MPE group (P＜0.05), and the mesothelial cell count decreased after drainage in the MPE group (P＜0.05). Conclusion The characteristics of pleural effusion changed greatly before and after drainage in patients with CHFPE. The cellular composition changed greatly before and after pleural effusion drainage in patients with MPE. The reliability of PE and pathological results should be carefully interpreted in combination with the time of specimen examination.

Key words: pleural effusion, drainage, tuberculosis, pleura, pleural effusion, malignancy, pneumonia, para effusion,
transudate