Pleural thickening

What is pleural thickening?

Pleural thickening is often linked to exposure to asbestos. It is the thickening and hardening of the pleura, the protective membrane surrounding the lungs.

Pleural thickening can occur in two forms:

• Diffuse pleural thickening extends over a large area and may restrict expansion of the lungs
• Pleural plaques - localised areas of pleural thickening/calcification that do not usually interfere with breathing

What causes pleural thickening?

Asbestos fibres settle in the lung tissues and irritate the pleura causing scarring and hardening. This scarring is irreversible.

There are several other causes of pleural thickening that are not related to asbestos exposure, including:

• Infections in the lungs such as tuberculosis
• Inflammation of the pleura
• Injuries such as bone fractures to the ribs
• Certain medications including those used to treat cluster headaches, migraines and Parkinson's disease
• Blood clot in the artery of the lung (pulmonary embolism): A blood clot in the lung can interrupt blood supply to parts of the lung causing the tissue to die (necrosis). Pleural thickening can occur as part of the healing process.
• Radiation can effect and thicken the pleura of a patient with lung cancer
• Tumours: both benign and malignant tumours may invade the pleura and this gives the appearance of pleural thickening. The pleura is a very thin membrane and is usually not visible on x-rays of the chest. Anything that increases the tissue thickness of the pleura will appear on x-rays as this type of condition. This can occur when there is fibrosis of the pleura as in asbestos related pleural thickening or when tumour tissue invades the pleura. Even simple inflammation of the tissue cells may cause infiltration of the pleura and result in the thickening of the membrane