Pleural Thickening

What Is Pleural Thickening?

Pleural thickening develops when scar tissue thickens the delicate lining around the lungs (the pleura). Pleural thickening can develop following asbestos exposure or other conditions, such as infection. It may be a symptom of a more serious condition, such as malignant pleural mesothelioma.

Depending on the cause, pleural thickening may form in different parts of the pleura. To distinguish between types, doctors will use imaging scans to examine the following:

• Parietal pleura: The outer membrane of the lung attached to the chest wall
• Pleural space: The inner space between the visceral and parietal pleura
• Visceral pleura: The inner membrane directly covering the lung tissue

The location of the impacted pleura and amount of pleural scarring can help doctors determine the type.

Types of Pleural Thickening: Diffuse vs Focal

Doctors may diagnose patients with different types of pleural thickening. Pleural thickening may be organized into two categories: diffuse and focal.

• Diffuse pleural thickening (DPT): Thickening of 50% or more of either the left or right pleura. DPT may also be diagnosed in a patient with thickening of 25% or more of both pleurae. Mesothelioma-specific diffuse pleural thickening is thickening and scarring of the visceral pleura, which can lead to the collapse of the pleural space.
• Focal pleural thickening: Thickening confined to one or more specific areas of the pleura. Apical pleural thickening is one type of focal pleural thickening and involves the top-most portion of the pleura of one lung. A second type is biapical pleural thickening, which affects the top-most portions of the pleura of both lungs. Nodular pleural thickening creates raised bump-like nodules from scar tissue.

Pleural thickening may be categorized as unilateral or bilateral depending on if it affects the pleura of one or both lungs. Doctors may even choose to further define a diagnosis to help guide treatment decisions.

Is Pleural Thickening Serious?

Pleural thickening is not always serious. However, it can cause more noticeable symptoms as it progresses and begins to limit lung function. Pleural thickening may also indicate an underlying condition, such as malignant mesothelioma cancer.

In some cases, pleural thickening can be benign. Benign pleural thickening is not caused by cancer and will typically not impede the normal functioning of the lungs. However, benign pleural thickening can restrict lung function if the thickening becomes too advanced. This may impair breathing.

Whether malignant or benign, pleural thickening cannot be cured. However, treatment can help manage symptoms.

Does Pleural Thickening Impact Life Expectancy?

On its own, pleural thickening usually doesn't impact life expectancy. But it can be a symptom of a more serious underlying condition, like lung disease or mesothelioma. If so, prognosis may depend on the underlying condition.

Long-term effects of pleural thickening are fairly mild in most cases. It may cause shortness of breath, chest pain and, in rare cases, severe lung restriction.

How Does Pleural Thickening Relate to Mesothelioma?

Pleural thickening in mesothelioma patients develops as a result of prolonged asbestos exposure. Individuals may ingest or inhale asbestos fibers, which may become trapped in the pleura. There, the fibers irritate the lung lining, causing chronic inflammation.

Over time, this inflammation can lead to severe fibrosis, or scarring, of the lungs. The accumulating scar tissue can become thick enough to keep the lungs from fully expanding when a person inhales.

According to studies, pleural thickening is common among mesothelioma patients.

• In one overview of past studies, researchers reported that 88% of malignant pleural mesothelioma patients showed pleural thickening on CT scan images.
• In studies following patients over time, the incidence of asbestos workers who developed pleural thickening was between 5% and 13.5%. The workers developed the condition anywhere from 3 to 34 years after asbestos exposure.

What Causes Pleural Thickening?

Pleural thickening can be caused by infection, asbestos exposure, injury and more. Exposure to lung irritants and infectious diseases are some of the common causes of pleural thickening.

The cause can dictate the location, severity and progression of the pleural thickening. For example, pleural thickening caused by asbestos exposure typically develops in the visceral pleura and may be serious. Different causes may also impact which symptoms a patient experiences.

What Are the Symptoms of Pleural Thickening?

Pleural thickening can be a progressive disease, meaning the symptoms often become more severe over time. In early stages, pleural thickening is often asymptomatic. As such, the condition can be difficult to detect. Common symptoms that may arise include breathlessness during physical activity and chest pain.

Individuals may experience additional symptoms depending on the cause of the pleural thickening.

People experiencing any of these symptoms should contact a doctor. Though pleural thickening alone may not be serious, a doctor can conduct a thorough examination for an underlying cause.

How Is Pleural Thickening Diagnosed?

Pleural thickening may be diagnosed with imaging scans, such as computed tomography (CT) scans. A physical examination may also help diagnose the condition.

Methods used to detect and diagnose pleural thickening include:

• Chest X-ray: Healthy pleurae are not visible on an X-ray, but thickening at the very edges of the lung/pleura may be visible.
• CT scan: CT scans can help detect irregular thickness of the pleura, even if the scar tissue is only a few millimeters thick.
• Magnetic resonance imaging (MRI): MRIs can be used to detect thickening and other pleural malignancies.
• Physical examination: A physician can check for physical symptoms, such as altered breathing sounds.
• Positron emission tomography (PET scan): Though rarely used, pleural thickening may also appear on a PET scan.
• Ultrasound: Ultrasounds generally only detect thickening more than one centimeter in thickness.

If your doctor believes pleural thickening may be a sign of cancer or another condition, they may order additional tests, including biopsies.

Differentiating Pleural Thickening From Other Pleural Diseases

Pleural thickening may also develop alongside other conditions, such as pleural plaques and pleural effusion. Though these conditions may develop together, they are distinct in how they form and present symptoms.

• Pleural effusion is the buildup of fluid between the pleurae.
• Pleural plaques are the buildup of gray/white tissue on the pleura and areas of benign thickening. This condition most commonly develops in the parietal pleura.
• Pleural thickening is the buildup of scar tissue. This can develop in the visceral pleura, the membrane covering the surface of each lung, or the parietal pleura, the lung’s outer membrane.

It’s important for the doctor to differentiate these pleural diseases to develop the appropriate treatment plan.

How Is Pleural Thickening Treated?

Many cases of pleural thickening do not require treatment and are not life-threatening. However, the condition may advance, and patient symptoms may become uncomfortable. In these cases, doctors may recommend pulmonary rehabilitation or cessation of smoking, if applicable.

Pulmonary rehabilitation may be able to improve symptoms and quality of life for patients. A specialist can develop a customized plan based on an individual’s needs. Some common recommendations for patients to remedy pleural thickening include:

• Exercising regularly
• Improving diet and nutrition
• Learning breathing strategies
• Learning how to conserve energy

In rare, serious cases, patients may undergo a pleurectomy and decortication (P/D) surgical procedure to help relieve symptoms.

Doctors may administer pleural thickening treatment in conjunction with treatment for the underlying cause. For mesothelioma patients, medical professionals may recommend regular respiratory function tests. These tests can determine how well the lungs are working and monitor disease progression.

Doctors perform respiratory function tests that look at:

• Analyzing the diffusing capacity, or the transfer of oxygen from the lungs to the bloodstream
• Testing the lung volume, or how much air the patient’s lungs can hold

Doctors can use these results to recommend treatments for improving lung function and managing symptoms. They can also consider any underlying condition that may be causing pleural thickening and adjust the care plan accordingly.