9 Min Read
Last Updated: 05/23/2024
Fact Checked

Written by Karen Selby, RN | Medically Reviewed By Dr. Chelsea Alvarado | Edited By Walter Pacheco

What Is Pleural Effusion?

Pleural effusion is a buildup of fluid in the space or pleural cavity between the two layers of tissue called the pleura that cover the lungs and chest wall. Commonly called “‘water on the lungs,” pleural effusions can be benign or malignant. 

Uncomplicated pleural effusions are not life-threatening and can resolve within a few months without medical intervention. However, once a person has one pleural effusion, they are more likely to experience this condition again.

Pleural effusion in pleural mesothelioma
Diagram shows location of pleural effusion development.

The pleural cavity normally contains a small amount of fluid that allows the pleura to slide smoothly past each other as we breathe and helps the chest expand during inhalation. Too much fluid in the pleural space compresses the lungs, preventing them from expanding or taking in air. This is called a non-expandable lung. 

A 2023 observational study from Kyuongpook National University and Ajou University Medical Center noted that non-expandable lung is more prevalent in mesothelioma patients, and up to 90% of people with pleural mesothelioma experience pleural effusion. 

Types of Pleural Effusion

Pleural effusions are classified into two types: transudative and exudative. When a doctor takes a fluid sample from the pleural cavity, they can determine the type based on its characteristics.

Identifying the type of pleural effusion someone has can help narrow down potential causes. While certain conditions can cause both types of pleural effusion, many conditions cause one or the other.

Exudative and Transudative Pleural Effusions
  • Exudative: This occurs when a disease directly affects the pleura and causes fluid to leak out of blood vessels.
  • Transudative: This occurs when there is a fluid or protein imbalance in the body and is rarely the result of a problem with the pleura.

Mesothelioma-related pleural effusion is a type of exudative effusion. Cancer can result in excess fluid buildup and blocked blood vessels and lymph vessels. The fluid is cloudy and contains cells and proteins.

The fluid collection inside the lungs is not a type of pleural effusion. When fluid builds up within the lungs, it’s called pulmonary edema. While both conditions can cause similar symptoms — such as difficulty breathing — they have very different causes and treatments.

Causes of Pleural Effusion

Pleural effusion can result from various diseases, including cancers, infections and inflammatory conditions. When cancer causes a pleural effusion, it’s called a malignant effusion. Both mesothelioma and lung cancer commonly cause malignant effusions.

Even people without a mesothelioma diagnosis but who have been exposed to asbestos are at an increased risk of developing pleural effusions. Pleural effusions can signal a developing asbestos-related disease, such as pleural thickening, and contribute to its progression. The accumulation of scar tissue on the pleura characterizes pleural thickening. It can increase and spread after each effusion episode.

Causes of Pleural Effusion
  • Alcoholism
  • Asbestos exposure
  • Blood clot in the lung (pulmonary embolism)
  • Cancer, including mesothelioma
  • Heart failure
  • High blood pressure
  • Liver scarring (cirrhosis)
  • Pneumonia
  • Smoking
  • Surgery

In adults, the most common causes of transudative pleural effusions are congestive heart failure and liver scarring. Most exudative pleural effusions result from pneumonia and cancer, unlike malignant effusions, bacterial infections and inflammation cause pneumonia-related pleural effusions. If you have a pleural effusion, your doctor must obtain a fluid sample to determine the cause and the best treatment.

How Does Mesothelioma Cause Pleural Effusion?

Pleural mesothelioma can cause malignant pleural effusions when tumors or resulting swollen lymph nodes block the lymphatic drainage system and the blood vessels. This blockage causes fluid to back up into the pleural cavity. 

Pleural mesothelioma tumors can make substances that increase blood vessel leakiness,  allowing blood, lymphatic fluid and water to leave the vessels and enter the pleural cavity. These fluids build up, causing exudative pleural effusion. 

A pleural effusion is fluid that forms from the pleural lining, secreting usually as a blockage or as a result of mesothelioma in the pleural lining. Because the fluid compresses onto the chest wall, patients often present with severe chest pain.

Pleural mesothelioma can also cause cancer-related hypoalbuminemia or low blood levels of a protein called albumin. Albumin accounts for 50% of all blood protein and is essential for maintaining fluid balance. Without enough albumin, water can leak from blood vessels and collect in the pleural space or other body parts.

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Pleural Effusion Symptoms

Pleural effusion symptoms depend on how much the fluid impacts someone’s breathing. Some people have no symptoms at all. Many pleural effusion symptoms overlap with mesothelioma symptoms, including chest pain and dry cough. Constant chest pain with breathing is a sign of mesothelioma.

Common Pleural Effusion Symptoms
  • Dry cough
  • Fatigue (tiredness that doesn’t improve with rest)
  • Fever, if fluid becomes infected
  • Hiccups
  • Malaise (general feeling of discomfort)
  • Difficulty breathing when lying down (orthopnea)
  • Sharp chest pain with breathing
  • Rapid, shallow breathing
  • Shortness of breath (difficulty breathing)

Although pleural effusions can resolve independently, it’s best to consult a doctor for treatment if you have any of the above symptoms. Without treatment, pleural effusions can become infected or cause lung collapse.

Diagnosing Pleural Effusion

When your healthcare provider suspects pleural effusion, they’ll order a chest X-ray or CT scan to confirm its presence. The appearance of pleural effusion varies based on the amount of accumulated fluid.

Tools Used to Diagnose Pleural Effusion
  • Chest X-ray
  • CT scan
  • Ultrasound

People with pleural effusion, mainly one-sided, need thoracentesis to determine the cause. Thoracentesis involves ultrasound-guided fluid removal from the pleural cavity using a needle.

Diagnosing Mesothelioma From Pleural Effusions

To remove fluid from the pleural cavity, thoracentesis is necessary to help diagnose mesothelioma from a pleural effusion. This fluid is tested for cancer cells and other markers that can help doctors diagnose the cause of the effusion.

Patient Advocate Snehal Smart, M.D. at The Mesothelioma Center, explains, “That fluid is drained, and a cytology exam, which is the study of the cells, is performed to find any abnormal cells in that fluid. Any presence of mesothelial cancer cells would indicate a diagnosis of mesothelioma.”

If fluid testing results suggest mesothelioma, a doctor will order a biopsy. This tissue sample is then analyzed under a microscope to look for mesothelioma cells. A tissue biopsy is the most important diagnostic tool used to diagnose mesothelioma. 

Survivor Michael Bederman, for example,  experienced shortness of breath and pleural effusions for a year. When he requested a biopsy be done, a diagnosis of pleural mesothelioma was confirmed as the cause of his pleural effusions.

Pleural Effusion Treatment

Most treatments for pleural effusion focus on removing the fluid and improving symptoms. Standard treatment approaches include catheter placement, thoracentesis and pleurodesis. 

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Newer treatments involve the infusion of drugs, such as chemotherapy combined with immunotherapy, into the pleural cavity. These treatment options require more research to study their efficacy. So far, clinical studies have found potential benefits of using these strategies to treat pleural effusions that occur due to cancer. 

Catheter Placement

Catheter placement for pleural effusion involves placing a plastic tube in the pleural cavity to drain fluid. This fluid drains into a bag. The tube must be kept clean and dry to prevent infections.

Catheter Placement for Pleural Effusion
Diagram shows needle placement for draining fluid buildup.
Catheter Placement for Pleural Effusion

Having a catheter for recurrent pleural effusion is sometimes more convenient for people than thoracentesis procedures because it doesn’t require frequent trips to the doctor. An experienced nurse will come to your home to empty accumulated fluid and sanitize the equipment. 

Pleurectomy/Pleural Decortication

Pleurectomy/Decortication (P/D) is a two-part surgical procedure. During a pleurectomy, the doctor opens the chest cavity and removes the lung’s pleural lining, along with other cancerous tissue. After removal of the lining, any visible tumors from the lung surface are removed. 

This procedure is quite involved and often takes several hours to complete. The benefit is that P/D can extend survival and significantly increase the quality of life for eligible patients. P/D can be especially beneficial when combined with other forms of treatment, including chemotherapy, radiation therapy and immunotherapy. 

Pleurodesis and Thoracentesis

Both pleurodesis and thoracentesis involve removing excess fluid from the pleural cavity. These treatments aim to relieve pressure on the lungs and improve breathing.

Key Pleurodesis and Thoracentesis Facts
  • Removing excess fluid from the pleural cavity with pleurodesis and thoracentesis can improve symptoms.
  • In addition to fluid removal, pleurodesis involves attempting to close the pleural space permanently.
  • It’s important for patients to discuss the risks and benefits of both procedures with a surgeon to ensure safety.

During pleurodesis, the surgeon attempts to close the pleural cavity permanently to prevent further fluid buildup. To achieve this, the surgeon inserts a chest tube to deliver drugs that cause pleural inflammation and close the pleural space. 

Pleurodesis can cause significant pain-related side effects and isn’t always practical. As a result, this procedure should be reserved for people with better overall health and a life expectancy of at least several months.  

Prognosis for Pleural Effusion

The prognosis or outlook for pleural effusion depends on the cause. While the prognosis is generally poor for people with malignant pleural effusion, it can vary significantly for each individual patient.

People with pleural mesothelioma and pleural effusion tend to live a bit longer than people with lung cancer, living an average of almost a year compared to 2-3 months. Treating mesothelioma can extend people’s lives an average of two years, with some living even longer. 

Research in new and emerging therapies is ongoing to improve prognosis for malignant pleural effusion patients. For people with cancer-related pleural effusions, joining a support group can help survivors cope with the stress related to their diagnosis and prognosis. The Mesothelioma Center, for example, offers a private Facebook support group exclusively for mesothelioma patients, their families and caregivers.

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