What causes fluid accumulation in the lungs?

Estimated reading time: 10 minutes 31 seconds

What is Pleural effusion? What is pulmonary edema?

The condition, commonly referred to as fluid accumulation in the lungs, has two different medical forms. One is pulmonary edema, and the other is pleural effusion. First, let’s take a closer look at both of these concepts to understand their similarities and differences from a medical perspective.

The alveoli, or air sacs, in our lungs are essential for our respiratory system as they facilitate gas exchange. The alveoli sacs carry out this gas exchange by allowing oxygen to pass into the blood and carbon dioxide to be expelled. When fluid accumulates in these small air sacs instead of air, a condition called pulmonary edema occurs.

When the alveoli fill with fluid, the lungs have difficulty functioning properly. The inability of the lungs to function properly results in difficulty breathing and a decrease in oxygen transport to the rest of the body. This condition is not a disease in itself, but rather a serious symptom of an underlying problem related to heart function. For example, when the left ventricle of the heart cannot pump blood effectively, pressure in the blood vessels of the lungs may increase, causing fluid to leak into the lung tissue.

Pulmonary edema can develop suddenly (acute) or gradually over time (chronic). In both cases, urgent medical evaluation and treatment are necessary to avoid complications that can be life-threatening.

Pleural effusion is the accumulation of fluid between the lung membranes (pleura), i.e., in the space surrounding the lungs. This fluid collects between the membrane covering the outer surface of the lungs and the membrane covering the chest wall. It prevents the lungs from expanding, causing shortness of breath.

Although both are commonly referred to as “fluid in the lungs,” pulmonary edema is fluid accumulation inside the lungs, whereas pleural effusion is fluid accumulation between the membranes surrounding the lungs. Therefore, the diagnosis and treatment approaches are different.

What causes fluid accumulation in the lungs?

Commonly known as “fluid in the lungs,” this condition can actually refer to two different medical problems: pulmonary edema and pleural effusion. Both conditions are characterized by abnormal fluid accumulation around or inside the lungs. However, in these two examples, the condition occurs in different parts of the respiratory system and for different reasons.

To answer the question “What causes fluid in the lungs?” correctly, let’s first distinguish between these two conditions and answer the question for each one.

Pulmonary edema refers to the accumulation of fluid in the lung tissue, particularly in the alveoli, which are small air sacs responsible for oxygen exchange. The causes of pulmonary edema are generally divided into two categories:

• Cardiac pulmonary edema is usually the result of heart problems, most commonly congestive heart failure. When the left side of the heart cannot pump blood efficiently, pressure builds up in the blood vessels of the lungs and pushes fluid into the alveolar spaces.
• Non-cardiac pulmonary edema occurs without direct involvement of the heart. Instead, it can result from conditions that damage lung tissue or disrupt fluid balance, such as:
  • Acute respiratory distress syndrome (ARDS)
  • Inhalation of toxic substances
  • Severe infections or sepsis
  • Kidney failure
  • High altitude (as in high-altitude pulmonary edema)
  • Excessive medication or certain medications
  • Serious trauma or surgery

The term “water in the lungs” may also refer to pleural effusion, which is the accumulation of fluid between the layers of tissue (pleura) surrounding the lungs. Although this condition differs from pulmonary edema, it is often confused with it in everyday usage. Common causes of pleural effusion include:

• Pneumonia
• Heart failure
• Certain cancers
• Tuberculosis
• Liver or kidney disease
• Pleural inflammation (pleurisy)
• Autoimmune or rheumatic diseases
• Chest trauma

In summary, pulmonary edema is characterized by fluid buildup within the lungs and is often associated with heart or lung damage. Pleural effusion, on the other hand, is characterized by fluid buildup around the lungs and can be caused by a wider range of systemic or localized diseases.

Both conditions require immediate medical attention. Accurate diagnosis is crucial for determining the correct treatment method.

What are the symptoms of pulmonary edema?

The symptoms of pleural effusion may vary depending on the amount of fluid, its severity, the rate of accumulation, and the underlying cause. Small amounts of fluid accumulation may be asymptomatic, but moderate or large accumulations can seriously affect breathing performance.

The most common symptoms of pulmonary edema are listed below:

• Shortness of breath: Shortness of breath is the most common symptom. It may increase during physical activity or when lying on your back.
• Chest pain: It is felt as a sharp, stabbing pain. It may worsen with deep breathing, coughing, or movement.
• Dry cough: It is usually a persistent, non-productive cough.
• Rapid, shallow breathing: Rapid breathing may be caused by the lungs’ inability to fully expand.
• Fatigue and weakness: The body may feel exhausted due to insufficient oxygen supply.
• Fever: If the pleural effusion is caused by an infection (such as pneumonia or tuberculosis), fever may occur.
• Back or shoulder pain: In some cases, the pain may spread beyond the chest.

If pleural effusion develops rapidly, symptoms may appear suddenly and be severe. In this case, the patient may require immediate medical attention. Additionally, if the patient has other underlying diseases, they may experience additional symptoms depending on the type of disease. Therefore, it is important to consult a doctor for a definitive diagnosis and to have the necessary imaging tests performed. After the tests, your doctor will evaluate your condition correctly, make a diagnosis, and plan the appropriate treatment.

How is lung fluid accumulation diagnosed?

Pleural effusion diagnosis is made after the doctor listens to the patient’s complaints, physically examines the patient, and then performs some imaging and laboratory tests if deemed necessary. During this process, your doctor’s goal is not only to detect fluid accumulation in the lungs, but also to understand exactly where and why this fluid has formed.

The main methods used in the diagnosis of fluid accumulation in the lungs can be listed as follows:

• Physical examination: Your doctor will listen to the sounds in your lungs with a stethoscope. If there is pleural effusion, the sound heard in this area will be reduced or not heard at all. In addition, a dull percussion sound called “matity” may be heard in the area where the fluid is located.
• Imaging methods: After the physical examination, your doctor will make some preliminary assessments. To clarify these assessments, they may refer you to some imaging methods. The main methods are as follows.
  • Chest X-ray: This is the first imaging method used. If there is fluid accumulation in the pleural space, whiteness (opacity) is seen in the lower parts of the lung.
  • Ultrasonography: This is used to determine the amount and location of fluid more accurately. It is also preferred as a guide during the fluid sampling procedure (thoracentesis).
  • Computed tomography (CT): Used to understand the underlying cause of pleural effusion and to examine the lung tissue and pleural membranes in detail.
  • Thoracentesis (fluid sampling): If pleural effusion is detected in the patient, the doctor usually takes a sample of the accumulated fluid using a procedure called thoracentesis. The fluid is drained using a thin needle and analyzed in a laboratory for possible infections, inflammation, and cancer.

These analyses determine the cause of the fluid and indicate whether the pleural effusion is due to a systemic condition, such as heart failure, or a local problem, such as an infection or tumor. A proper treatment is planned based on the results.

How is pulmonary edema treated?

The goal of pulmonary edema treatment is to relieve symptoms such as shortness of breath and chest discomfort, remove excess fluid, and treat the underlying disease. Therefore, the treatment of pleural effusion depends on the cause of the fluid accumulation and how much fluid has accumulated.

The following list outlines the steps that may be taken during the treatment process.

Treatment of the underlying cause

The most important step in treating pleural effusion is to treat the underlying problem causing the fluid buildup. Once the source of the fluid and the cause of its accumulation are controlled, the effusion may resolve on its own. Some common causes of this problem include:

• Heart failure: Treated with diuretics and medications that improve heart function.
• Infection (e.g., pneumonia or tuberculosis): Treated with antibiotics or tuberculosis medications.
• Cancer-related effusion: May require chemotherapy, radiation, or targeted therapies.
• Autoimmune diseases: Treated with corticosteroids or other immune-modulating medications.

Drainage of fluid (thoracentesis)

When effusion causes severe difficulty or discomfort in breathing, a procedure called thoracentesis is performed. This procedure involves inserting a thin needle or tube into the chest wall to remove fluid. It provides immediate relief and can also aid in the diagnostic process by allowing the fluid to be examined.

Recurrent or complicated effusions

In some cases, especially if the fluid returns frequently or becomes infected, more advanced interventions may be necessary. These interventions can be listed as follows:

• Chest tube placement: Especially in cases of empyema (infection of the fluid), a tube may be placed in the chest for continuous drainage.
• Pleural desis: This procedure involves injecting a chemical substance (such as talc) into the pleural space to prevent the lung from adhering to the chest wall and to prevent future fluid accumulation. It is commonly used in cases of fluid accumulation associated with cancer.
• Pleural catheter: If effusions are chronic and recurrent, a small, tunnel-shaped catheter may be placed to allow patients to drain fluid at home.
• Surgical: In rare and complex cases, procedures such as video-assisted thoracoscopic surgery (VATS) may be required to remove thick fluid, infected tissue, or tumors.