Pleural Effusion: Causes, Symptoms, and Types of Fluid in Lungs
Know what pleural effusion is, recognising the signs and symptoms, causes, diagnosis and prevention and more.
Written by Dr. M L Ezhilarasan
Reviewed by Dr. Mohammed Kamran MBBS, FIDM
Last updated on 16th Sep, 2025
Introduction
Have you been experiencing a persistent, dry cough or a strange, sharp pain in your chest when you take a deep breath? Perhaps you’ve noticed an unexplained shortness of breath that’s gradually getting worse, even when you’re just resting. These could be more than just signs of a common cold; they might be key indicators of a condition called pleural effusion, often colloquially known as ‘water on the lungs.’
This condition isn’t a disease itself but a serious symptom of an underlying health issue, where excess fluid builds up in the pleural space, the thin area between the lungs and the chest wall. This buildup puts pressure on your lungs, making it difficult and often painful to breathe. This article will guide you through the common signs of pleural effusion, delve into the various causes that lead to it, and explain the different types of fluid that can accumulate.
Recognising the Signs: Symptoms of Pleural Effusion
The symptoms of a pleural effusion can vary widely. Some people with a small effusion may have no symptoms at all and only discover it incidentally on an X-ray taken for another reason. However, as the volume of fluid increases, it begins to compress the lung, leading to noticeable and often distressing signs.
Common Symptoms Everyone Should Know
The most frequently reported symptoms are directly related to the lung's inability to expand fully:
- Shortness of breath (Dyspnea): This is the hallmark symptom. You may feel breathless during physical activity and, in more advanced cases, even while lying down or at rest.
- Chest pain: This is often a sharp, stabbing pain that worsens with deep breathing or coughing (a condition known as pleurisy or pleuritic pain). The pain is usually felt on the side of the effusion.
- Dry, non-productive cough: The irritation and pressure on the lung tissue can trigger a persistent cough that doesn't produce phlegm.
Consult a Pulmonologist for Personalised Advice
When It's an Emergency: Severe Symptoms
Large or infected effusions can lead to more severe symptoms that require immediate medical attention:
- Fever and chills, especially if the effusion is caused by an infection like pneumonia, leading to an empyema (pus in the pleural space).
- Difficulty breathing when lying flat (orthopnea).
- A feeling of heaviness or tightness in the chest.
If you experience a sudden, severe onset of these symptoms of fluid around the lungs, it is imperative to seek emergency care promptly.
The Root of the Problem: What Causes Pleural Effusion?
A pleural effusion is always a consequence of another disease process. The underlying causes of water on the lungs are broadly categorised by how they affect the delicate pressure system in the blood vessels, which leads us to the different types of effusion.
Causes of Heart Problems (Transudative)
The most common cause worldwide is congestive heart failure. When the heart doesn't pump efficiently, pressure backs up in the blood vessels, particularly those leading to the lungs. This increased hydrostatic pressure forces fluid out of the vessels and into the pleural space. Other causes in this category include liver cirrhosis (causing hepatic hydrothorax) and kidney disease (like nephrotic syndrome), where low protein levels in the blood reduce the osmotic force that keeps fluid in the vessels.
Causes of Lung Inflammation and Infection (Exudative)
This occurs when diseases cause inflammation that makes the blood vessel walls "leaky," allowing protein-rich fluid, cells, and other substances to seep out. Common culprits include:
- Pneumonia: A lung infection that often causes parapneumonic effusions.
- Pulmonary embolism: A blood clot in the lungs.
- Autoimmune diseases: Lupus and rheumatoid arthritis can cause inflammation of the pleura itself (pleuritis).
The Link to Cancer: Malignant Pleural Effusion
Cancer is a major cause of exudative effusions. Lung cancer, breast cancer, lymphoma, and ovarian cancer are the most common cancers that spread (metastasise) to the pleura. These cancer cells disrupt the normal fluid dynamics and often lead to recurrent, significant fluid buildup, a condition known as malignant pleural effusion, which signifies advanced disease.
Other Less Common Causes
These include trauma leading to blood in the space (hemothorax), leakage from the lymphatic system (chylothorax), and complications from certain medications.
Not All Fluid is the Same: Types of Pleural Effusion
Understanding the difference between transudative and exudative effusions is the most critical classification, as it directly points doctors toward the underlying cause.
Transudative Pleural Effusion: A Pressure Issue
This type is caused by an imbalance in the hydrostatic and oncotic pressures within otherwise normal blood vessels. The fluid is a clear, watery ultrafiltrate of plasma with low protein content. Think of it as a systemic pressure problem "pushing" fluid out. The pleura itself is not diseased. Causes are usually heart, liver, or kidney failure.
Exudative Pleural Effusion: A Leaky Vessel Issue
This type is caused by inflamed, diseased, or damaged blood vessels in the pleura that have become "leaky." The fluid is protein-rich, often cloudy, and can contain white blood cells or cancer cells. This indicates a local lung or pleural disease like infection, cancer, or inflammation.
- Special Types: Hemothorax, Empyema, and Chylothorax
- Hemothorax: Effusion consisting of blood, usually from chest trauma.
- Empyema: A collection of pus (infected fluid) in the pleural space, a serious complication of pneumonia.
- Chylothorax: Effusion of milky-white lymphatic fluid (chyle) due to trauma or blockage to the thoracic duct.
How do Doctors Diagnose and Classify the Effusion?
It includes:
Imaging Tests: X-rays and CT Scans
A chest X-ray is the first and most common test to confirm the presence of fluid. It can show a characteristic white meniscus (curve) at the bottom of the lung. A CT scan provides much more detail, showing the exact location, amount of fluid, and can often reveal the underlying cause, such as a tumour or pneumonia.
The Definitive Test: Thoracentesis and Fluid Analysis
This is the key diagnostic procedure. A doctor inserts a needle through the chest wall (under local anaesthesia and ultrasound guidance) to withdraw a sample of the fluid. This fluid is then analysed in a lab. Using Light's Criteria (a set of measurements including protein and LDH levels), the lab definitively classifies the fluid as transudate or exudate. Further analysis can look for infection (Gram stain, culture), cancer cells (cytology), and other markers, making the thoracentesis procedure the gold standard for diagnosis.
If your doctor recommends a thoracentesis procedure to analyse the fluid, Apollo24|7 can help coordinate the necessary imaging and specialist consultation to streamline your diagnosis.
Treating the Fluid and the Cause
The treatment has two parallel goals: relieving the immediate symptoms by removing the fluid and treating the underlying condition to prevent it from coming back.
Draining the Fluid: Thoracentesis and Chest Tubes
A therapeutic thoracentesis can drain a large amount of fluid at once, providing immediate relief from shortness of breath. For larger, infected, or recurrent effusions, a larger chest tube may be inserted to drain continuously over several days.
Addressing the Underlying Condition
This is the most important part of long-term management:
- For heart failure: Diuretics ("water pills") to reduce overall fluid volume.
- For pneumonia: Powerful antibiotics.
- For cancer: Chemotherapy, radiation, or targeted therapy aimed at the tumours.
Procedures for Recurrent Effusion: Pleurodesis and Shunts
For recurrent malignant pleural effusion that doesn't respond well to other treatments, a procedure called pleurodesis may be performed. A chemical or talc is inserted into the pleural space to irritate the membranes, causing them to stick together and seal the space, preventing future fluid buildup. In some cases, a permanent indwelling catheter may be placed for drainage at home.
Can Pleural Effusion Be Prevented?
You cannot directly prevent pleural effusion itself, as it is a complication of other diseases. Therefore, the best prevention strategy is to proactively manage any underlying chronic conditions you may have. This includes:
- Strictly follow your treatment plan for heart failure, liver disease, or kidney disease.
- Quitting smoking drastically reduces your risk of lung cancer and COPD.
- Getting recommended vaccines (like pneumococcal and flu vaccines) to prevent infections that can lead to pneumonia.
Seeking early medical attention for persistent respiratory symptoms like a cough or shortness of breath. Early diagnosis of the underlying cause is the best way to prevent complications like a significant effusion.
Conclusion
Understanding pleural effusion is about connecting the dots between the symptoms you feel, the type of fluid present, and the underlying disease causing it. While the experience of shortness of breath can be frightening, recognising it as a potential sign of fluid around the lungs is the first step toward effective treatment. The critical distinction between a transudative and exudative effusion guides healthcare providers directly to the root cause, whether it's a systemic issue like heart failure or a local problem like lung cancer. If you or a loved one is experiencing these symptoms, especially if they are persistent or worsening, do not dismiss them.
Consult a Pulmonologist for Personalised Advice
Consult a Pulmonologist for Personalised Advice
Dr. Keshavan. V.
Pulmonology Respiratory Medicine Specialist
10 Years • "MBBS (CMC, Vellore) MD (CMC, Vellore) DNB EDARM (France) SCE(UK) ATSF (USA) MRCPS (Glasgow) FCCP (USA) FAPSR (Japan) MNAMS"
Hyderguda
Apollo Hospitals Hyderguda, Hyderguda
Dr. Sumara Maqbool
Pulmonology Respiratory Medicine Specialist
12 Years • MBBS, DNB Respiratory, critical care and sleep medicine, DrNB superspeciality Critical care, IDCCM, IFCCM, EDIC
Delhi
Apollo Hospitals Indraprastha, Delhi
(25+ Patients)
Dr. Srikar Darisetty
Pulmonology Respiratory Medicine Specialist
11 Years • MBBS, MD, DM (Pulmonary & Critical Care Medicine), DNB, EDRM (Switzerland), FSM (Sleep Medicine), MRCP (UK) SCE
Hyderabad
Apollo Hospitals Jubilee Hills, Hyderabad
(200+ Patients)
Dr. Debopam Chatterjee
Pulmonology/critical Care Specialist
10 Years • MBBS, MD, DNB, DM(Pulmonary, Critical care & Sleep Medicine, AIIMS), European Diploma of Adult Respiratory Medicine CONSULTANT INTERVENTIONAL PULMONOLOGIST, & SLEEP MEDICINE SPECIALIST.
Kolkata
Apollo Multispeciality Hospitals , Kolkata, Kolkata
(75+ Patients)
Dr. Pravin Madhukar Tajane
Pulmonology Respiratory Medicine Specialist
10 Years • MBBS, MD (Pul. Med.), IDCCM
Nashik
Apollo Hospitals Nashik, Nashik
Consult a Pulmonologist for Personalised Advice
Dr. Keshavan. V.
Pulmonology Respiratory Medicine Specialist
10 Years • "MBBS (CMC, Vellore) MD (CMC, Vellore) DNB EDARM (France) SCE(UK) ATSF (USA) MRCPS (Glasgow) FCCP (USA) FAPSR (Japan) MNAMS"
Hyderguda
Apollo Hospitals Hyderguda, Hyderguda
Dr. Sumara Maqbool
Pulmonology Respiratory Medicine Specialist
12 Years • MBBS, DNB Respiratory, critical care and sleep medicine, DrNB superspeciality Critical care, IDCCM, IFCCM, EDIC
Delhi
Apollo Hospitals Indraprastha, Delhi
(25+ Patients)
Dr. Srikar Darisetty
Pulmonology Respiratory Medicine Specialist
11 Years • MBBS, MD, DM (Pulmonary & Critical Care Medicine), DNB, EDRM (Switzerland), FSM (Sleep Medicine), MRCP (UK) SCE
Hyderabad
Apollo Hospitals Jubilee Hills, Hyderabad
(200+ Patients)
Dr. Debopam Chatterjee
Pulmonology/critical Care Specialist
10 Years • MBBS, MD, DNB, DM(Pulmonary, Critical care & Sleep Medicine, AIIMS), European Diploma of Adult Respiratory Medicine CONSULTANT INTERVENTIONAL PULMONOLOGIST, & SLEEP MEDICINE SPECIALIST.
Kolkata
Apollo Multispeciality Hospitals , Kolkata, Kolkata
(75+ Patients)
Dr. Pravin Madhukar Tajane
Pulmonology Respiratory Medicine Specialist
10 Years • MBBS, MD (Pul. Med.), IDCCM
Nashik
Apollo Hospitals Nashik, Nashik
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Frequently Asked Questions
What is the most common cause of a pleural effusion?
Globally, congestive heart failure is the most common cause of transudative pleural effusion. In cases of exudative effusions, pneumonia and lung cancer are among the leading causes.
Can pleural effusion go away on its own?
A very small, asymptomatic effusion caused by a minor viral infection might resolve as the infection clears. However, most clinically significant effusions require medical treatment to drain the fluid and address the underlying cause. They typically will not go away on their own.
What is the life expectancy for someone with a malignant pleural effusion?
A malignant pleural effusion indicates that cancer has spread, and it is generally associated with a shortened life expectancy, often measured in months. However, this varies greatly depending on the type of cancer, its responsiveness to treatment, and the patient's overall health. It is crucial to discuss prognosis with your oncologist.
Is pleural effusion painful?
It can be. Many people experience pleuritic chest pain—a sharp pain that worsens with deep breathing or coughing. However, some effusions cause only a dull ache or a feeling of pressure and heaviness, while others may cause no pain at all.
How long does it take to recover from a thoracentesis?
The procedure itself takes about 15-30 minutes. The immediate recovery involves lying on the opposite side for an hour or so to ensure no bleeding or leakage. Most people can go home the same day and resume normal activities within 24 hours, though they are advised to avoid strenuous activity for a day or two.