You can know that there is fluid in the pleural cavity after lung nodule surgery by methods such as X-ray, ultrasound and CT examination. After lung nodule surgery, you can know that there is fluid in the chest cavity by X-ray examination. X-ray examination shows that the lungs in the chest cavity are black, and if there is a white part and the angle of the rib diaphragm is blunt, then there may be fluid in the chest cavity. The presence of pleural effusion can be known by ultrasound after lung nodule surgery. Ultrasound has high sensitivity to pleural effusion and accurate localization, which is clinically used for the estimation of the volume and depth of effusion, and can assist in the localization of thoracentesis. CT examination can be used to know that there is fluid in the pleural cavity after lung nodule surgery. CT examination has high sensitivity and density resolution for pleural lesions, and it can easily find a small amount of fluid that is difficult to be shown on X-ray radiographs, and it can determine exudate, blood or pus according to the difference in the density of the pleural fluid. Therefore, patients with pleural effusion after lung nodule surgery do not need to be too anxious, a small amount of effusion can be self-absorbed, if the amount of effusion is large, standardized treatment should be carried out under the guidance of the doctor.