Pleural Thickening
Pleural thickening is an increase in thickness of the pleura, the thin lining that covers the lungs and the inside of the chest wall. It often appears on imaging as a band or plaque of dense tissue along the surface of the lung. Pleural thickening can result from prior infection, inflammation, asbestos exposure, trauma, prior surgery, or, less commonly, a tumor of the pleura. Many cases are mild and stable, but in some patients, pleural thickening can restrict lung expansion or signal an underlying condition that requires further evaluation.
What is it?
The pleura is a thin, two-layered membrane that surrounds each lung. One layer covers the lung itself (the visceral pleura), and the other lines the inside of the chest wall (the parietal pleura). A small amount of fluid between the two layers allows the lungs to glide smoothly during breathing. Pleural thickening occurs when this normally thin membrane becomes thicker, either in a localized area (often called a pleural plaque) or in a more diffuse pattern along the surface of the lung.
Pleural thickening has many possible causes. Prior infections, such as pneumonia, empyema (infected fluid around the lung), or tuberculosis, can leave behind areas of thickening after they heal. Inflammatory conditions—including connective tissue diseases such as rheumatoid arthritis—can also cause pleural changes. Asbestos exposure is a well-known cause of pleural plaques, which often appear years or decades after exposure and are typically a marker of prior contact with asbestos rather than active disease. Trauma, prior chest surgery, hemothorax (blood in the pleural space), and radiation therapy can also lead to pleural thickening. Less commonly, pleural thickening reflects a tumor of the pleura itself, such as mesothelioma, or spread of cancer from elsewhere in the body.
Many people with pleural thickening have no symptoms, particularly when the changes are mild or limited to small plaques. When symptoms occur, they generally relate to reduced lung expansion. Patients may notice shortness of breath, especially with exertion, chest discomfort, or a feeling of tightness. More extensive pleural thickening can limit how fully the lungs expand and reduce exercise tolerance. In some cases, an underlying condition (such as ongoing infection, inflammation, or tumor) produces additional symptoms such as fever, weight loss, or cough.
CT of the chest is the primary imaging test for evaluating pleural thickening because it provides detailed views of the pleura, lungs, and chest wall, and can identify features that help suggest the underlying cause. Imaging features that may raise concern for malignancy include nodular or irregular thickening, thickening involving the mediastinal pleura, circumferential thickening encasing the lung, associated pleural effusion, or invasion of nearby structures. PET/CT and MRI may be used in selected cases. When the cause is uncertain or when there is concern for malignancy, pleural fluid analysis or image-guided biopsy may be performed. Chest X-ray is often the initial study but is less detailed than CT.
Important to Know
Treatment of pleural thickening depends on the underlying cause and the severity of any symptoms. Many cases are stable findings related to old infections, healed inflammation, or prior asbestos exposure and require no specific treatment beyond periodic monitoring. When pleural thickening is associated with an active condition—such as ongoing infection, inflammatory disease, or malignancy—treatment is directed at that condition. For patients with significant symptoms from extensive pleural thickening, pulmonary rehabilitation, treatment of associated effusion, and, rarely, surgical procedures such as pleural decortication may be considered.
Because pleural thickening can sometimes be the first clue to an important underlying diagnosis, imaging findings are interpreted together with the patient’s history of infections, occupational and environmental exposures, prior cancers, and current symptoms. In patients with known asbestos exposure, ongoing follow-up is often recommended even when the thickening itself is asymptomatic.
Red flag symptoms include rapidly worsening shortness of breath, chest pain, coughing up blood, unintended weight loss, persistent fever, or rapid growth of pleural thickening on follow-up imaging. These warrant prompt medical evaluation, as they may indicate infection, active inflammatory disease, or malignancy.