Pleural effusion. Coloured side X-ray of the lungs of a 60-year-old patient with a pleural effusion of the left lung. The front of the body is at left, with the spine at right. The lungs are in the space between the spine and the breast bone (upper left). The patient has a pleural effusion, an accumulation of fluid (lower left, pink) in the chest cavity. Below the fluid is the diaphragm and upper abdomen (white). The liquid is compressing the left lung, which leads to breathing difficulties. An effusion is treated by aspiring (draining) the fluid, which relieves the pressure.