Decortication in treatment of mesothelioma

Decortication is a medical procedure involving the removal of part or all of the outer surface layer, membrane, or fibrous cover of an organ such as the lung, kidney, or brain. It is most commonly performed on the lungs. There is a cavity between the lung and the chest wall called the pleural space or cavity. Decortication is done to remove the lining of the pleural cavity, called the pleura, when this lining becomes thick and inelastic, restricting lung expansion. It is also done to remove tumors in the pleura. The goals of the operation are to re-expand the lung and fix the problems affecting the pleural space to improve lung function.

Decortication may be necessary to help patients with pleurisy, empyema, fibrothorax and mesothelioma. Pleurisy is an inflammation of the lining of the pleural cavity surrounding the lungs, which can cause painful respiration and other symptoms. Pleurisy can be generated by a variety of infectious and non-infectious causes.

Fibrothorax, a form of pleurisy, is defined as the presence of abnormal fibrous tissue within the pleural space, resulting in entrapment of the underlying lung tissue (a state also referred to as trapped lung, restrictive pleurisy, or encased lung). Although any injury to the pleura can result in the inflammatory response with fibrous deposition that leads to fibrothorax, blood accumulation in the pleural cavity and bacterial infections remain the most common causes of fibrothorax.

An empyema is a pus within a natural body cavity. In humans, the pleural space surrounding the lungs is most commonly affected. Typically, empyemas evolve over a 4- to 6-week period as the infection progresses throughout the pleural space. This condition is called pyothorax and is usually caused by a bacterial infection of the lungs or pneumonia. The first phase is characterized by a thin, fibrous fluid accumulating. The second phase is characterized by a heavy fibrous deposit over the pleural surface with the development of fibrous debris. The third phase, which begins at about 3 to 5 weeks, is characterized by the formation of a thick fibrous peel imprisoning the lung and preventing expansion. When fully developed, this peel has three distinct layers: (1) an outer layer consisting of blood vessels, (2) a middle layer consisting of fibrous tissue that is mostly without blood vessels and cells, and (3) an inner layer with dying tissue and fibrous masses. Generally, if there is a small amount of blood accumulated, it will be reabsorbed. However, if there is relatively large amount of blood, if there is continued bleeding, or if bacteria are present, there is a high likelihood that a fibrous peel will eventually form. Decortication is the surgical procedure to peel away this restrictive fibrous layer from the lung.

Malignant mesothelioma is a form of cancer that is almost always caused by previous exposure to asbestos. In this disease, tumors develop in the protective lining that covers most of the body's internal organs; the most common site is the outer lining of the lungs and chest cavity. Decortication is performed to remove the tumors.

Decortication Procedure

Decortication is performed under general anesthesia. It is a major operation requiring an incision of the chest wall. This small incision is made in the chest cavity at the appropriate predetermined space between ribs (usually the fifth or sixth space). Surgeons may also insert an instrument fitted with a lighting system and telescopic attachment, designed to permit visual inspection within the chest cavity through this incision in the chest wall.

When the disease has lasted longer than 6 weeks, the pleural layers are often fused together making decortications more challenging. When adhesions are present between the pleural layers but the pleural layers are not fused together the adhesions may be torn apart.

An incision is made in the outside layer of the pleura, and the appropriate place to start decortication is identified. The fibrous peel is grasped with a clamp, and dissected over a broad area to separate the peel from the underlying pleura. During this part of the procedure, it is possible for injuries to occur to the fragile underlying lung tissue, causing air leaks. This operation often becomes tedious since for an optimal outcome, all portions of the lung encased by the peel should be addressed. So, it is often necessary to follow the peel into the opening, down onto the diaphragm, and into the grooves. At times, a second entry point into the chest may be needed to remove all the peel and this second incision is made through another space between the ribs. All of the outside pleural peel with fibrous tissue is removed and any pus present is drained from the pleural space.

Once removed, the pleural peel is sent for laboratory evaluation. The lung is tested to confirm that it is capable of complete re-expansion. Any large air leaks that are noted may be sewn up, but this step often is not necessary. Instead, sealants are used that control air leaks in the lung tissue. Chest tubes are placed along the diaphragm and provided that the lung is satisfactorily re-expanded, air leaks will seal promptly.

Risks

There are a times when decortication is not suitable, such as when a patient is unfit to undergo surgery or there is an underlying lung or bronchial disease that would prevent lung re-expansion. The mortality to be expected after decortication depends on the severity of the underlying illness and on the occurrence of complications. In 1985, mortality was less than 8%. Complications tend to be either infection related or technique related (e.g., hemorrhage, and persistent air leakage); some of them may necessitate additional surgeries. As with all chest operations, close attention to detail and proper surgical technique are critical for minimizing complications.

Outcome

Decortication for mesothelioma, alone or in combination with other therapies is disappointing, with a 5 year survival rate of less than 10%. Successful decortication depends on whether the patient was suitable for surgery, using correct techniques, and quickly addressing any complications after surgery. If any of these principles are overlooked, decortication may not achieve any significant improvement for the patient, potentially leaving him or her worse than before.