An encapsulated pleural effusion is a pleuritis in which adhesions between the dirty and mural pleura cause the effusion to be confined to a single part of the chest cavity, usually arising in the lower lateral posterior chest wall. On imaging X-rays, the clinical picture of encapsulated effusion may show a shadow protruding from the chest wall toward the lung field, appearing as a semicircle or a flat mound, with the upper and lower edges of the shadow at an obtuse angle to the chest wall, which can be seen clearly and with a uniform density, often in tuberculosis. In pleurisy, the adhesions produced by the pleura of the dirty wall layer cause the fluid to be confined to one part of the thoracic cavity, forming an encapsulated effusion. Most of them are wrapped in the axillary margin or against the posterior chest wall. When the patient is turned to the tangential position, the film may show a dense shadow projecting from the chest wall into the chest, appearing semicircular or spindle-shaped, with uniform density and clear sharp edges. Subpulmonary effusion is the fluid that accumulates between the base of the lung and the diaphragm. It is mostly unilateral, with the right side being more common. Because the fluid pushes the lower edge of the lung upward, the X-ray shows an increase in density in the lower lung field, which is continuous with the diaphragm shadow, while the upper edge has an upwardly protruding dome shape, which is easily mistaken for diaphragm elevation. However, subpulmonary effusion has the following characteristics: 1) the highest point of the “diaphragmatic dome” is 1/3 lateral, and the angle of the rib diaphragm becomes deeper and sharper; 2) the lower border of the liver is seen in normal position under fluoroscopy; 3) in supine fluoroscopy, the symptoms are reflected in the uniformly increased density of the lung field on the affected side. 4) when tilted 60° to the affected side, the sign of free effusion can be seen; a few patients In a few patients, pleural adhesions may appear at the base of the lung and the fluid cannot flow. The main method of treatment for encapsulated pleural effusion is to combine X-ray or ultrasound imaging with localization, puncture at a specific site, and aspirate the fluid in the cavity or inject drugs.