Decortication

Decortication is a surgical procedure that removes a restrictive layer of fibrous tissue overlying the lung, chest wall, and diaphragm. The aim of decortication is to remove this layer and allow the lung to reexpand. When the peel is removed, compliance in the chest wall returns, the lung is able to expand and deflate, and patient symptoms improve rapidly. ^[1]

In most people, the pleural space is less than 1 mm thick. When this space is violated by any number of pathologic disorders, the distribution of certain cells and fluid can be altered, with serious medical consequences. ^[2]  One common pathologic process that affects the pleural space is fibrothorax, which is an abnormal accumulation of fibrous tissues over the lung or visceral pleura. The deposition of fibrous tissues over the lung parenchyma can be so intense that the underlying lung fails to expand. Over time, the lung becomes entrapped or encased. ^[1]

Although decortication is an effective surgical procedure for this condition, its success depends on careful selection of patients. As in all thoracic surgery procedures, the preoperative workup should be thorough, and the surgery should be done at a particular timed interval. Moreover, the surgeon should also be technically skilled at entering the chest and removing the peel. In some cases, the intercostal space is fused, and it is almost impossible to enter the chest cavity.

The primary indication for decortication in a patient with fibrothorax is presence of symptoms due to lung restriction resulting from development of a thick fibrinous peel. ^[3]  The timing of surgery is vital for success. In many cases, the peel may spontaneously resolve, and the symptoms may subside. ^[4]  Most surgeons will perform a decortication for the following conditions:

• The pleural peel has been present for more than 4-6 weeks
• Lung symptoms are disabling
• There is radiologic evidence of a trapped lung

Decortication is frequently necessary when other minor interventions (eg, chest tube) have not resulted in clearance of the infection or hemothorax. Tuberculous empyema is usually first treated with drugs, and decortication is only undertaken after long-term drug therapy fails.

Pleurectomy-decortication has been described in the treatment of malignant pleural mesothelioma. ^{[5, 6, 7, 8]}  Pleurectomy-decortication may be defined as consisting of total parietal and visceral pleurectomy with sparing of the pericardium and the hemidiaphragm, whereas extended pleurectomy-decortication may be defined as the above plus resection of the pericardium and the hemidiaphragm when required. ^[9]

Other than physiologic unfitness on the part of the patient, there are no absolute contraindications for decortication. In some patients who also have underlying lung disease, removal of the peel may not help the lung expand, and thus surgery would be futile.

Other conditions that may make decortication futile include the presence of a pleural-space infection and large-airway stenosis. In such cases, the lung will not expand to fill the pleural space. A more extensive pleuropneumonectomy may be the sole available option, but only if the patient has been worked up preoperatively. Pleuropneumonectomy is a major undertaking with a very high mortality.

Decortication may not be possible in the presence of uncontrolled lung infection or contralateral lung disease or for a chronically debilitated patient. Medical optimization may be required before surgery is undertaken in these patients. Ideally, the patient's nutritional status should first be normalized (with nasogastric feedings if necessary), and sepsis should be controlled with appropriate antibiotic therapy.

Other relative contraindications include coagulopathy, severe chest-wall infection, and terminal disease.

Anatomy

The boundaries of the pleural space are the visceral pleura, which envelops the lungs, and the parietal pleura, which is the inner lining of the thoracic cavity. ^[10]  The goals in performing decortication are to remove all the fibrinous peel and necrotic tissue, to help the lung reexpand, and, equally important, not to leave any residual air spaces. ^[11]

The two most common problems encountered in performing decortication are pleural-cavity infection and fibrosis. ^[12]  It is difficult for the underlying lung to expand when there is a thick peel overlying the parenchyma. Consequently, there is a large residual space left in the chest cavity that almost always becomes infected. Therefore, for the surgeon to have good success with decortication, the timing of surgery is crucial.

If the disease has been chronic, the rib spaces are often fused, and the chest cavity is severely constricted. Entry into the chest can be very difficult. If the peel is very thick and adherent, injury to the lung parenchyma can occur with moderate air leak. If the lung has an inherent disorder, the possibility of reexpansion may not occur. Finally, decortication is not a trivial procedure and can be very bloody; thus, the patient must also be physiologically fit enough to undergo the procedure. All these factors must be considered in planning a decortication. ^[13]

Moreover, once the chest cavity has been entered, no lung may initially be visible because of the thick fibrous peel. The peel can vary in thickness from a few millimeters to few centimeters. One may also find necrotic debris and abscess along the chest cavity. It is important to avoid dissection along the medial border of the lung because the heart chambers are close by. The dissection should be started on lateral aspects or near the fissures. In most cases, the lower lobe is fused with the diaphragm, and one can easily enter the abdominal cavity if the dissection is too deep.

For safe decortication, the chest cavity is best entered at the fifth or sixth intercostal space, and dissection should be started where the peel is the thinnest and easily removed. It is important to reassess the anatomy every few minutes to prevent injury to the organs. Blind digital peeling should be avoided, especially near the apex of the lung. This area is best approached when the upper lobe can be retracted inferiorly and the lung apex is visible. Severe bleeding from injury to the subclavian vessels and pulmonary artery has been reported.

Because extensive decortication or radical pleurectomy can be associated with air leaks, methods have been described for reconstructing the diaphragm so as to help lower the incidence of postoperative complications. ^{[14, 15, 16]}

When performing video-assisted thoracoscopic surgery (VATS), one must be aware of the adjacent structures to avoid injury. On the superior aspect, the subclavian vessels can be found lying deep to the pleura but clearly visible. Along the medial border, one may come across the thymus, the trachea, the heart, the phrenic nerve, the aorta (on the right), the vena cava (on the left), and the esophagus (posteriorly). In the posterolateral chest, one may come across the sympathetic chain, the azygos vein, and the diaphragm (inferiorly). ^{[1, 10]}

Procedural planning

Decortication gives the best results in patients who seek early treatment. Fibrothorax is a time-dependent process and can be prevented. Depending on the cause, insertion of a chest tube to remove an effusion or hemothorax may prevent the development of fibrothorax.

Among patients with chest trauma who have a hemothorax, placement of a chest tube and complete drainage usually prevents development of fibrothorax. Numerous studies have shown that early and complete evacuation of clotted hemothorax and parapneumonic effusions leads to decreased morbidity and mortality.

Some of the reasons that may explain an incomplete return of lung volume include elevation of the diaphragm, mediastinal shift, intercostal muscle fibrosis, or decrease in size of the thoracic cavity. Some experts believe that the longer the empyema is allowed to progress, the lower the likelihood that lung function will return back to normal. Although some authors report an association between shorter course of disease and improved outcomes, this is not a universal finding among all surgeons.

Although studies have not explained failure of the lung to expand after so-called successful decortication, the most likely reason is either technical difficulties or incomplete removal of the peel. In many cases, the plane of dissection can be difficult. Too much persistence in removing the thin peel can also injure the underlying lung parenchyma and result in massive air leaks.

Inability to define the plane of dissection between the peel and the visceral pleura is an especially troublesome technical challenge that can adversely affect results. If visceral pleurectomy is performed, air leakage and postoperative hemorrhage may compromise pulmonary function. Care must be taken throughout the operation to protect the phrenic nerve from injury; fortunately, this usually is not an issue, because the mediastinal pleura is rarely involved in the inflammatory process. Incomplete parietal pleurectomy or inability to free the diaphragm may also compromise results.

If patients are appropriately selected, complete reexpansion of the lung after decortication can usually be achieved. Occasionally, however, an issue related to residual pleural space might arise after an otherwise technically satisfactory decortication. If this space is not obliterated, failure is inevitable.

The results after decortication are often fruitful. Morbidity and mortality after this procedure are dependent on patient age, underlying comorbidities, and development of complications from the surgery. In general, decortication has an excellent outcome in young people.

In younger patients with benign causes of fibrothorax, outcome is typically excellent and quality of life much improved. ^[17]  Most patients begin to feel relief of symptoms soon after surgery. In elderly patients with multiple comorbidities, recovery is often slow, but symptom relief is also better. The majority of patients regain their previous exercise endurance and are able to return to their original work.

However, when the procedure is done in patients with compromised lung function, morbidity can be high. Besides surgery itself, the thoracic incision and general anesthesia also carry a high morbidity in people with no lung reserve. Older data suggest that overall mortality in healthy people is less than 1% but may run as high as 4-6% in individuals with underlying lung disease. With VATS, however, mortality figures have tended to be slightly lower. ^{[18, 19, 16]}

To avoid complications, the surgeon must pay attention to detail. The peel should be removed with great care, and injury to nearby organs should be avoided. If the decortication is done adequately, lung function improves remarkably. However, the ultimate return of lung function depends on preoperative lung disease.

If the lung parenchyma was normal prior to surgery, then complete reexpansion of the lung and obliteration of the pleural space is certainly possible. In most cases, lung volumes improve after decortication, but it is rare to see a return to preoperative values.