The lungs lie in the chest cavity inside a bony cage made up of ribs. The inside of the chest cavity and the outer surface of the lungs are lined by a thin membrane called the pleura. The pleural lining produces a small amount of fluid that acts as a lubricant.
A pleural effusion is a buildup of fluid between the layers of pleura – around the lung. Two different types of effusions can develop:
Transudative pleural effusions: These are caused by fluid leaking into the pleural cavity. This is caused by increased pressure in, or low protein content in, the blood vessels. Heart failure is the most common cause of this type of pleural effusion.
Exudative effusions: These are caused by blocked blood vessels, inflammation such as tuberculosis, lung injury, and drug reactions. In addition, cancers arising in the lung or spreading to the chest cavity from other organs also produce such a fluid collection – malignant pleural effusion.
Hemothorax: This is the collection of liquefied blood or bloody fluid in the chest cavity. This may occur trauma to the chest.
Pleural Effusion
If after a physical examination, the doctor suspects a pleural effusion one of the following tests are ordered to confirm it.
Chest x-ray
Blood tests to determine the likely cause of the fluid
CT scan of the chest
Pleural fluid analysis: A small amount of fluid is drawn with the help pf a needle and sent for analysis for its composition as well as examination under a microscope to look for bacteria and presence of cancer cells.
Chest x-ray showing large pleural effusion on left side
The treatment of fluid in the chest is directed at the underlying disease causing it. For example, in heart failure medicines are administered to improve the function of the heart and clear the fluid. Sometimes it becomes necessary to remove a substantial quantity of fluid so that the lung can expand well and the breathing can improve. At times, a tube may have to be placed in the chest cavity for a few days / weeks to drain the fluid out.
A chest tube placed to drain fluid from the chest
Thoracoscopic surgery of video-assisted thoracoscopic surgery (VATS) is a form of “key hole’ procedure that allows doctors to see inside the chest cavity to help in the diagnosis and treatment of fluid in the chest.
For diagnosis: At times, despite several investigations the cause for the accumulation of fluid may not be clear and the fluid keeps filling up after it is removed. In such cases thoracoscopy can be performed for looking inside the chest cavity and obtaining biopsy samples which can confirm the precise diagnosis. The biopsy may confirm an infection or a cancerous process as the underlying cause.
The operation is performed under general anaesthesia. During thoracoscopic operations the surgeon makes two to three small (about 1-cm) incisions and places tube called cannulas through the chest wall. To look inside the chest, the surgeon passes a telescope connected to a miniature video camera through one of the cannulas. The video camera picks up the picture of the inside of the chest cavity and transmits it to a television screen. The surgeon then carries out the operation with the help of special instruments introduced inside the chest through other cannulas and by observing the picture of the operative site on the television screen. At the end of the surgery usually a thin tube is placed in the chest cavity through the small incisions used for placing the cannulas. This tube drains out the fluid or air that may collect inside after surgery. The tube is removed after a few days.
For evacuation of fluid: When the fluid collecting in the chest cavity is liquefied blood, it does not often drain well through a tube. Such a collection may get infected and delay recovery. Thoracoscopic surgery allows the surgeon to clear out all the blood and a film that often forms over the lung so that the lung can expand again.
Chemical pleurodesis: This literally means coming together or fusion of the two layers of the pleura so that the space is obliterated and no further fluid can collect in the space. This is achieved by spraying an irritant such as talc powder or a chemical like povidone iodine or bleomycin in the pleural cavity under the control of thoracoscopic vision. The inflammatory reaction caused by the chemical makes the two layers of the pleura stick together. A tube has to be left in place for a few to several days till drainage of fluid stops completely.
