Pleural Effusion
A pleural effusion is the buildup of excess fluid between the layers of tissue that line the lungs and the inside of the chest (the pleura). This fluid can accumulate for many reasons, including infection, heart failure, inflammation, liver disease, or cancer. Pleural effusions can be small and cause no symptoms, or large enough to make breathing difficult and require medical evaluation.
What is it?
A pleural effusion forms when fluid collects in the pleural space—the thin gap between the lung and chest wall. This space normally contains only a small amount of lubricating fluid, but certain conditions can disrupt the balance between fluid production and absorption. The accumulated fluid can compress the lung, reduce normal breathing capacity, and cause symptoms depending on the amount and speed of buildup.
Pleural effusions can be caused by many underlying conditions. Common causes include heart failure, pneumonia, lung injury, autoimmune disease, liver or kidney disease, and cancers involving the lungs or pleura. Imaging helps determine the size, appearance, and possible cause of the effusion, and may guide further testing such as thoracentesis.
Important to Know
CT scans, chest X-rays, and ultrasound can all detect pleural effusions, and ultrasound is often used to guide fluid drainage when needed. Identifying the underlying cause is essential, as treatment focuses on resolving both the effusion and the condition that led to it. Some effusions resolve with medication alone, while others may require repeated drainage or additional procedures.
Urgent symptoms include severe shortness of breath, chest pain, fever, or coughing up blood—these may indicate infection, significant fluid buildup, or another serious condition. Individuals with a history of cancer, heart failure, or chronic lung conditions should particularly monitor new or worsening breathing symptoms. Most pleural effusions improve once treated appropriately, but follow-up imaging is often recommended to ensure resolution.