Fibrothorax

Fibrothorax is often a complication of other diseases that cause inflammation of the pleura. These include infections such as an empyema or tuberculosis, or bleeding within the pleural space known as a haemothorax. Exposure to certain substances, such as asbestos, can cause generalised fibrosis of the lungs, which may involve the pleura and lead to fibrothorax.[7] Less common causes of fibrothorax include collagen vascular diseases such as systemic lupus erythematosus, sarcoidosis, and rheumatoid arthritis; kidney failure leading to uraemia; and side effects of certain medications.[3][8] The medications most commonly associated with pleural fibrosis are the ergot alkaloids bromocriptine, pergolide, and methysergide.[3] Fibrothorax may also occur without a clear underlying cause, in which case it is known as idiopathic fibrothorax.

A technique called pleurodesis can be used to intentionally create scar tissue within the pleural space, usually as a treatment for repeated episodes of a punctured lung, known as a pneumothorax, or for pleural effusions caused by cancer. While this procedure usually generates only limited scar tissue, in rare cases a fibrothorax can develop.[6]

Fibrosis can affect one or both of the two layers of tissue forming the pleura—the visceral pleura adjacent to the lung and the parietal pleura adjacent to the ribcage. The term fibrothorax implies severe fibrosis affecting both the visceral and the outer (parietal) pleura, fusing the lung to the chest wall.[2] The condition starts as an undrained pleural effusion. Over time, the undrained pleural effusion causes sustained inflammation of the pleura, which can then lead to deposition of fibrin in the pleura and the development of a fibrotic scar. Eventually, a "peel" that is rich in collagen forms around the fluid collection. From this point, the illness can no longer be treated with thoracentesis, since the fluid will return to the cavity maintained by the peel.[4]

Over time, generally over the years, the fibrotic scar tissue slowly tightens and thickens, contracting the contents of one or both halves of the chest and reducing the mobility of the ribs. The peel can become deeper than 2 cm.[2] Within the chest, the lung is compressed and unable to expand (trapped lung), making it vulnerable to collapse and causing breathlessness.[7] Restrictive lung disease from fibrothorax may occur when pleural fibrosis is so severe that it involves the diaphragm and ribcage and results primarily from decreased rib movement.[3]

A fibrothorax can typically be diagnosed by taking an appropriate medical history in combination with the use of appropriate imaging techniques such as a plain chest X-ray or CT scan.[3] These imaging techniques can detect fibrothorax and pleural thickening that surround the lungs.[7] The presence of a thickened peel with or without calcification are common features of fibrothorax when imaged.[3] CT scans can more readily differentiate whether pleural thickening is due to extra fat deposition or true pleural thickening than X-rays.[3]

If a fibrothorax is severe, the thickening may restrict the lung on the affected side causing a loss of lung volume.[7] Additionally, the mediastinum may be physically shifted toward the affected side.[3] A reduction in the size of one side of the chest (hemithorax) on an X-ray or CT scan of the chest suggests chronic scarring.[6] Signs of the underlying disease causing the fibrothorax are also occasionally seen on the X-ray.[6] A CT scan may show features similar to those seen on a plain X-ray.[7] Lung function testing typically demonstrates findings consistent with restrictive lung disease.[6]

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  Extensive left-sided fibrothorax
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  Chest radiograph displaying inhomogeneous opacification of the left half of the chest that is fibrothorax
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  Chest X-ray (left) and CT scan (right) demonstrating fibrothorax
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  Autopsy specimen showing extensive pleural fibrosis

Fibrothorax complicating another condition, such as tuberculous pleuritis, empyema, or acute haemothorax often spontaneously resolves in 3-6 months.[3]

The prognosis after surgical decortication is variable and depends on the health of the underlying lung before the procedure takes place.[3] If the lung was otherwise healthy, then certain aspects of lung function, such as vital capacity, may improve after decortication.[3] If, however, the lung had significant disease, then lung function often does not improve and may even deteriorate after such intervention.[3] The duration of fibrothorax does not affect prognosis.[3]

The mortality of surgery is less than 1% overall, but rises to 4-6% in the elderly. Other factors predicting poorer surgical outcomes include intraoperative complications, incomplete surgery, lung disease beyond the fibrothorax being treated, and specific causes of fibrothorax such as asbestosis.[10]

Sporadic cases are rarely reported in the medical literature, for example, due to iatrogenic or postoperative complications. Fibrothorax is rare in developed countries, mainly due to a lower incidence of tuberculosis. The condition is far more common in workers exposed to asbestos, with 5–13.5% of those exposed subsequently developing some degree of pleural fibrosis, sometimes not diagnosed until decades after the initial exposure.[9]