Thoracentesis: Draining Fluid from Around Your Lungs

What Is Thoracentesis and Why Is It Done?

Thoracentesis, also called a pleural tap or pleural aspiration, is a medical procedure that removes excess fluid from the pleural space—the thin area between your lungs and chest wall. It is performed both to relieve breathing difficulties caused by fluid buildup and to diagnose the underlying cause of pleural effusion.

Your lungs are surrounded by a thin membrane called the pleura, which has two layers: one covering the lungs and one lining the inside of the chest wall. Normally, there is only a small amount of lubricating fluid between these layers that helps your lungs move smoothly during breathing. However, various medical conditions can cause abnormal amounts of fluid to accumulate in this space, a condition known as pleural effusion.

When excess fluid builds up in the pleural space, it compresses the lung and limits its ability to expand fully. This can cause symptoms such as shortness of breath, chest pain or discomfort, a persistent cough, and difficulty taking deep breaths. The larger the amount of fluid, the more severe these symptoms tend to be. Some patients with significant pleural effusions may feel breathless even at rest or when lying down.

Thoracentesis serves two primary purposes in medical care. First, it can be therapeutic, meaning the procedure is performed specifically to remove fluid and relieve symptoms. Removing even a moderate amount of fluid can dramatically improve breathing and quality of life. Second, thoracentesis can be diagnostic, allowing doctors to analyze the fluid in a laboratory to determine what is causing the effusion. The characteristics of the fluid—including its appearance, chemical composition, and cell content—provide crucial clues about the underlying condition.

Common Causes of Pleural Effusion

Many different medical conditions can lead to fluid accumulation around the lungs. Understanding the cause is essential for proper treatment. The most common causes include:

• Heart failure: When the heart cannot pump blood efficiently, fluid can back up into the lungs and pleural space. This is one of the most common causes of pleural effusion.
• Pneumonia and lung infections: Infections can cause inflammation that leads to fluid accumulation. In some cases, this fluid can become infected itself (empyema).
• Cancer: Lung cancer, breast cancer, lymphoma, and other cancers can spread to the pleura and cause malignant pleural effusions.
• Liver disease: Cirrhosis and other liver conditions can cause fluid to accumulate in both the abdomen and the pleural space.
• Kidney disease: Kidney failure can lead to fluid overload throughout the body, including the pleural space.
• Pulmonary embolism: Blood clots in the lungs can cause pleural effusions.
• Autoimmune diseases: Conditions like rheumatoid arthritis and lupus can cause pleural inflammation and fluid buildup.

Transudative vs. Exudative Effusions

Medical professionals classify pleural effusions into two main types based on the fluid's characteristics. Transudative effusions are typically caused by systemic conditions that affect fluid balance, such as heart failure, liver cirrhosis, or kidney disease. The fluid in these cases is usually clear and watery with low protein content.

Exudative effusions, on the other hand, result from local inflammation, infection, or cancer affecting the pleura directly. This type of fluid typically has higher protein content and may contain more cells, including white blood cells or even cancer cells. Distinguishing between these types helps doctors narrow down the underlying cause and choose appropriate treatment.

What Are the Different Types of Pleural Drainage?

There are two main methods for draining pleural fluid: needle aspiration (thoracentesis/pleural tap) for smaller volumes or diagnosis, and chest tube drainage (tube thoracostomy) for larger volumes or ongoing drainage. The choice depends on the amount of fluid, the underlying cause, and whether repeated drainage will be needed.

When you have a pleural effusion that requires drainage, your medical team will choose the most appropriate method based on your specific situation. The two primary approaches differ in how they access the pleural space and how long the drainage device remains in place.

Needle Aspiration (Thoracentesis)

Needle aspiration, also called thoracentesis or pleural tap, involves inserting a needle through the chest wall into the pleural space to withdraw fluid. This method is typically used when a smaller amount of fluid needs to be removed—usually up to about 1.5 liters—or when the primary goal is to obtain a sample for diagnostic testing.

The procedure is relatively quick, typically taking about 15-30 minutes depending on how much fluid is being removed. After the fluid has been withdrawn, the needle is removed, and a small bandage is applied to the puncture site. Most patients can go home the same day after a brief observation period. If the underlying condition causes fluid to reaccumulate, thoracentesis may need to be repeated.

Thoracentesis is particularly useful when doctors need to analyze the fluid to determine what is causing the effusion. Even a small sample—about 50-100 milliliters—can provide valuable diagnostic information. The fluid is sent to a laboratory where technicians examine its appearance, measure its protein and sugar content, count the cells present, and look for bacteria or cancer cells.

Chest Tube Drainage (Tube Thoracostomy)

When larger amounts of fluid need to be drained, or when drainage needs to continue over several days, doctors may place a chest tube—a flexible plastic tube that remains in the pleural space and continuously drains fluid into a collection bag. This approach, also called tube thoracostomy or pleural drainage, is more invasive than needle aspiration but more effective for managing large effusions.

Placing a chest tube involves making a small incision in the skin and creating a pathway between the ribs into the pleural space. The tube is then inserted and secured in place with stitches. The external end of the tube connects to a drainage system that allows fluid to flow out while preventing air from entering the pleural space.

Patients with chest tubes typically need to stay in the hospital for one to several days, depending on how much fluid needs to drain and the underlying cause. Healthcare staff monitor the amount and appearance of the drainage and remove the tube once drainage has slowed significantly. The insertion site is then bandaged and usually heals within a few weeks.

Indwelling Pleural Catheters

For patients with recurrent pleural effusions—particularly those caused by cancer or other chronic conditions—doctors may recommend an indwelling pleural catheter. This is a thin, flexible tube that remains permanently in place and allows patients to drain fluid at home as needed.

The catheter is tunneled under the skin to reduce the risk of infection, and a valve at the external end keeps it closed when not in use. Patients learn to connect the catheter to a drainage bottle and drain fluid themselves, typically every 1-3 days or when they notice increased breathlessness. This approach gives patients more control and reduces the need for repeated hospital visits.

How Should I Prepare for Thoracentesis?

Preparation for thoracentesis typically includes blood tests to check clotting function, an imaging study to locate the fluid, and discussing any blood-thinning medications with your doctor. You may need to stop certain medications temporarily before the procedure.

Proper preparation helps ensure that your thoracentesis procedure is as safe and effective as possible. Your healthcare team will provide specific instructions based on your individual situation, but there are several general steps that most patients will need to follow.

Blood Tests and Imaging

Before the procedure, your doctor will typically order blood tests to evaluate your clotting function. These tests—including a complete blood count, platelet count, and coagulation studies (PT/INR)—help identify any bleeding risks that might need to be addressed before the procedure. If your blood does not clot properly, the risk of bleeding complications increases.

Imaging studies are essential for planning the procedure. Your doctor will need to know exactly where the fluid is located and how much is present. A chest X-ray is often the first imaging study performed and can show the presence and approximate size of a pleural effusion. However, ultrasound provides much more detailed information and is now considered the standard of care for guiding thoracentesis.

Ultrasound allows the doctor to see the fluid collection in real time, measure its depth, and identify the safest insertion point—one that avoids the liver, spleen, and major blood vessels. Studies have consistently shown that ultrasound-guided thoracentesis has fewer complications than procedures performed without imaging guidance.

Medications to Discuss

It is crucial to tell your doctor about all medications you are taking, including prescription drugs, over-the-counter medications, and supplements. Some medications can increase bleeding risk and may need to be temporarily stopped before the procedure.

Blood-thinning medications (anticoagulants) such as warfarin, heparin, rivaroxaban (Xarelto), apixaban (Eliquis), and dabigatran (Pradaxa) may need to be paused before thoracentesis. Your doctor will tell you exactly when to stop these medications and when it is safe to resume them. This decision depends on balancing the bleeding risk from the procedure against the risk of blood clots if you stop your anticoagulant.

Antiplatelet medications like aspirin and clopidogrel (Plavix) may also need to be stopped, depending on why you take them and your overall bleeding risk. Never stop any medication without discussing it with your doctor first.

Allergy Information

Tell your healthcare team if you have ever had an allergic reaction to local anesthetics (such as lidocaine) or any other medications. Local anesthesia is used to numb the area before the needle is inserted, and your team needs to know about any previous reactions so they can use an alternative anesthetic if necessary.

Also mention any latex allergies, as some medical equipment may contain latex. Your healthcare team can ensure that latex-free supplies are used if needed.

What to Expect on the Day of the Procedure

You do not typically need to fast before thoracentesis, though your doctor may have specific instructions. Wear comfortable, loose-fitting clothing that is easy to remove, as you will need to expose your back and side for the procedure. Leave jewelry and valuables at home.

Plan to have someone drive you home after the procedure, especially if you are receiving any sedation. Even if you feel fine, it is best to have support available. Most patients can return to normal activities within a day or two, but you should avoid strenuous exercise and heavy lifting for at least 24-48 hours.

What Happens During a Thoracentesis Procedure?

During thoracentesis, you sit upright leaning forward while the doctor uses ultrasound to locate the fluid. The skin is cleaned and numbed with local anesthetic, then a needle is inserted between your ribs to drain the fluid. The procedure takes 15-30 minutes and you remain awake throughout.

Understanding what will happen during your thoracentesis can help reduce anxiety and allow you to cooperate effectively with the medical team. The procedure follows a standardized sequence designed to maximize safety and comfort while effectively draining the pleural fluid.

Positioning

Proper positioning is essential for a successful and safe thoracentesis. You will typically sit upright on the edge of the bed or an examination table, leaning slightly forward with your arms resting on a pillow placed on a bedside table. This position accomplishes several important goals: it allows gravity to pool the fluid at the lower part of the pleural space where it is easiest to access, it moves the diaphragm downward to reduce the risk of puncture, and it provides the doctor with good access to your back where the needle will be inserted.

If you are unable to sit upright—for example, if you are very ill or on mechanical ventilation—the procedure can be performed with you lying on your side or even on your back, though these positions may be somewhat less optimal. Your healthcare team will help you find the most comfortable position that still allows safe access to the fluid.

Ultrasound Guidance

Before any needles are inserted, the doctor will use an ultrasound machine to locate the fluid and plan the safest insertion point. The ultrasound probe is placed on your back and moved around to visualize the fluid collection from different angles. The doctor can see exactly where the fluid is located, how deep it is, and where nearby structures like the diaphragm, liver, and spleen are positioned.

The doctor will mark the optimal insertion site on your skin—typically in the lower part of your back, between the ribs. This mark indicates where the needle will enter. Using ultrasound guidance has been shown to significantly reduce the risk of complications, including pneumothorax (collapsed lung) and accidental puncture of other organs.

Skin Preparation and Local Anesthesia

Once the insertion site is identified, the area is thoroughly cleaned with antiseptic solution to minimize the risk of infection. The cleaning solution may feel cold on your skin. Sterile drapes are then placed around the site to maintain a clean field.

Next, local anesthetic (usually lidocaine) is injected to numb the skin and deeper tissues. You will feel a brief stinging or burning sensation as the anesthetic is injected—this is typically the most uncomfortable part of the procedure. The doctor injects anesthetic along the planned needle path, including the tissue between the ribs and the lining of the chest wall (parietal pleura), which is particularly sensitive.

After a minute or two, the area will be fully numb. You may still feel pressure during the remainder of the procedure, but you should not feel sharp pain. Tell your doctor immediately if you experience significant pain, as additional anesthetic can be given.

Needle Insertion and Fluid Drainage

With the area numb, the doctor inserts the thoracentesis needle through the skin and between the ribs into the pleural space. You may feel a sensation of pressure or "give" as the needle passes through the chest wall and enters the fluid-filled space. Many patients also feel an urge to cough when the needle first enters the pleural space—this is normal and usually brief.

Once the needle is properly positioned, fluid begins to flow through it into a collection system. For diagnostic thoracentesis, only a small amount of fluid (50-100 mL) is removed and sent for laboratory analysis. For therapeutic thoracentesis, larger amounts are drained to relieve symptoms—typically up to 1-1.5 liters, though sometimes more.

During drainage, you will be asked to remain as still as possible and to avoid coughing. Deep breathing, sudden movements, or coughing could shift the needle's position. If you feel the need to cough, tell your doctor so they can temporarily stop the drainage. You may feel a sensation of relief as the fluid is removed and your lung begins to expand more fully.

Completion and Bandaging

Once sufficient fluid has been removed—or if you develop coughing, chest tightness, or pain that suggests the procedure should stop—the needle is withdrawn. A small bandage or adhesive dressing is placed over the puncture site. The entire procedure typically takes 15-30 minutes from start to finish.

What Should I Expect After Thoracentesis?

After thoracentesis, you will rest for at least one hour while being monitored. Most patients can go home the same day and return to normal activities within 1-2 days. Some pain at the puncture site is normal and can be managed with over-the-counter pain medication.

The recovery period after thoracentesis is usually straightforward, but there are important things to know about what to expect and how to care for yourself in the days following the procedure.

Immediate Post-Procedure Period

Immediately after the procedure, you will be asked to rest in a comfortable position while healthcare staff monitor your vital signs. This observation period typically lasts at least one hour and may be longer if a large amount of fluid was drained or if there are any concerns.

Many patients experience immediate relief from shortness of breath after thoracentesis. As the lung re-expands into the space previously occupied by fluid, you may notice that breathing feels easier and more comfortable. This improvement can be dramatic, especially if you had a large effusion.

A chest X-ray is often performed after the procedure to check that the lung has expanded properly and to look for any complications such as pneumothorax. If this imaging shows normal findings and you feel well, you will typically be discharged to go home.

Managing Discomfort at Home

It is normal to experience some discomfort at the puncture site for a few hours to a few days after the procedure. This may feel like soreness, a dull ache, or tenderness when you move or take deep breaths. Over-the-counter pain medications such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) are usually sufficient to manage this discomfort. Follow the dosing instructions on the package and do not exceed the recommended dose.

The bandage on your puncture site can usually be removed after 24-48 hours. Keep the area clean and dry during this time. You can shower after the bandage is removed, but avoid soaking in a bathtub, swimming pool, or hot tub for at least a week to reduce infection risk.

Small amounts of fluid or blood-tinged drainage from the puncture site are normal and expected for the first day or two. This occurs because the wound is still healing and any residual fluid or blood is working its way out. Use a clean bandage to absorb any drainage and change it as needed.

Activity Restrictions

Most patients can return to light activities and work within a day or two of the procedure. However, you should avoid strenuous exercise, heavy lifting, and activities that strain your chest muscles for at least 24-48 hours. If you had a large amount of fluid drained or if you had any complications, your doctor may recommend a longer recovery period.

Listen to your body during recovery. If an activity causes significant discomfort or shortness of breath, stop and rest. Gradually increase your activity level as you feel comfortable. Most people feel back to normal within a few days.

If You Have a Chest Tube or Indwelling Catheter

Recovery is different if you have a chest tube that remains in place for continuous drainage. You will need to stay in the hospital while the tube is in place, and healthcare staff will monitor the drainage and care for the tube. Pain at the tube insertion site is common and is managed with prescription pain medication.

If you go home with an indwelling pleural catheter, you will receive detailed instructions on how to drain the fluid yourself, how to care for the catheter, and what signs of problems to watch for. Home health nurses may also visit to help with drainage and catheter care, especially initially.

What Are the Risks and Possible Complications?

Thoracentesis is generally safe when performed with ultrasound guidance by experienced physicians. The most common complication is pneumothorax (air in the pleural space), occurring in 1-5% of cases. Other rare complications include bleeding, infection, and injury to nearby organs.

Like any medical procedure, thoracentesis carries some risks. However, advances in technique—particularly the routine use of ultrasound guidance—have significantly reduced the complication rate. Understanding the potential complications can help you make an informed decision and know what warning signs to watch for.

Pneumothorax

Pneumothorax, or collapsed lung, is the most common complication of thoracentesis. This occurs when air enters the pleural space, either from the lung being accidentally punctured by the needle or from air entering through the needle track. The incidence of pneumothorax after thoracentesis ranges from about 1% to 5%, depending on the technique used and the skill of the operator. Ultrasound guidance has significantly reduced this risk.

Most cases of post-thoracentesis pneumothorax are small and resolve on their own without treatment. Your medical team will monitor you after the procedure and may obtain a chest X-ray to check for this complication. If a pneumothorax is detected and is small, you may simply be observed until it resolves. Larger pneumothoraces may require placement of a chest tube to remove the air.

Bleeding

Bleeding can occur at the puncture site or, less commonly, inside the pleural space. Minor bleeding at the skin puncture site is common and not serious—it usually stops with gentle pressure and leaves only minor bruising. More significant bleeding, called a hemothorax, is rare and typically occurs only if a blood vessel is accidentally punctured during the procedure.

The risk of bleeding is higher in patients who take blood-thinning medications or who have abnormal clotting function. This is why your doctor checks your blood clotting tests before the procedure and may ask you to temporarily stop certain medications.

Infection

Introduction of bacteria into the pleural space during thoracentesis is rare but can cause a serious infection called empyema. Strict sterile technique during the procedure minimizes this risk. Signs of infection—such as increasing pain, redness around the puncture site, fever, or worsening shortness of breath—may not appear until several days after the procedure.

Re-expansion Pulmonary Edema

When a large amount of fluid is removed quickly, the lung re-expands rapidly into space it has not occupied for some time. In some cases, this rapid re-expansion can cause the lung tissue to become swollen and waterlogged—a condition called re-expansion pulmonary edema. This complication is more likely when more than 1.5 liters of fluid is removed in a single session or when the lung has been compressed for a long time.

Symptoms of re-expansion pulmonary edema include coughing, chest tightness, and worsening shortness of breath that may develop within hours of the procedure. To minimize this risk, doctors typically limit the amount of fluid removed in a single session and stop drainage if you develop significant coughing or chest discomfort.

Injury to Other Organs

The liver, spleen, and diaphragm are located near the base of the lungs and could theoretically be injured during thoracentesis if the needle is inserted too deeply or in the wrong location. Ultrasound guidance virtually eliminates this risk by allowing the doctor to visualize these structures and avoid them.

What Happens If the Fluid Comes Back?

Whether pleural fluid recurs depends on the underlying cause. Treating conditions like heart failure often prevents recurrence, while cancer-related effusions frequently reaccumulate. Options for recurrent effusions include repeated thoracentesis, indwelling pleural catheters, or pleurodesis (a procedure that prevents fluid reaccumulation).

One of the most common concerns patients have after thoracentesis is whether the fluid will return. The answer depends largely on what is causing the pleural effusion in the first place. Understanding your specific situation and the available options for managing recurrent effusions can help you plan for the future.

When Fluid Typically Does Not Recur

If your pleural effusion was caused by a treatable condition that can be resolved, the fluid usually does not return once the underlying problem is addressed. For example, a parapneumonic effusion—fluid that develops alongside pneumonia—typically resolves permanently once the infection is treated with antibiotics and the inflammation subsides. Similarly, effusions caused by pulmonary embolism usually do not recur once the blood clot is treated with anticoagulant medications.

Heart failure is a more nuanced situation. Pleural effusions related to heart failure often improve with diuretic medications and other heart failure treatments. If your heart failure is well-controlled, you may not need another thoracentesis. However, if your heart failure worsens or becomes difficult to manage, fluid may reaccumulate.

When Fluid Commonly Recurs

Malignant pleural effusions—those caused by cancer—have a high rate of recurrence. The underlying cancer continues to cause inflammation and fluid production, often leading to reaccumulation within weeks of drainage. For patients with recurrent malignant effusions, repeated thoracentesis can become burdensome, and alternative approaches are usually recommended.

Effusions related to liver cirrhosis (hepatic hydrothorax) also commonly recur because the underlying condition causes ongoing fluid shifts. Similarly, patients with end-stage kidney disease may experience recurrent effusions related to fluid overload.

Options for Recurrent Effusions

Several options exist for managing pleural effusions that return repeatedly:

Repeated thoracentesis: For patients who tolerate the procedure well and have slow fluid reaccumulation, periodic thoracentesis (every few weeks to months) may be a reasonable approach. This remains an option as long as the procedure continues to provide symptom relief.

Indwelling pleural catheter (IPC): As mentioned earlier, this is a thin tube that remains in place permanently, allowing patients to drain fluid at home as needed. IPCs are particularly useful for patients with malignant effusions or other causes of rapid fluid reaccumulation. Many patients can manage drainage themselves or with the help of family members, reducing hospital visits.

Pleurodesis: This is a procedure that intentionally creates scarring between the two layers of the pleura, sealing them together so that fluid can no longer accumulate between them. Pleurodesis can be performed by injecting an irritating substance (such as talc or doxycycline) through a chest tube, or surgically through video-assisted thoracoscopic surgery (VATS). Pleurodesis is most effective when the lung can fully expand after fluid drainage.

VATS pleurectomy: For some patients, particularly those with trapped lung (where the lung cannot fully expand), surgical removal of part of the pleura may be recommended. This is a more invasive approach but can provide lasting relief.

How Can I Manage Living with Pleural Effusion?

Living with recurrent pleural effusion requires working closely with your healthcare team to manage symptoms and address the underlying cause. Strategies include monitoring for symptoms, adhering to treatment plans, staying active as tolerated, and seeking support for the emotional aspects of chronic illness.

For some patients, pleural effusion is a one-time event that resolves with treatment. For others, particularly those with chronic conditions like cancer or heart failure, managing pleural effusion becomes an ongoing part of life. Understanding how to live well with this condition can improve your quality of life.

Monitoring Your Symptoms

Learning to recognize when fluid is reaccumulating allows you to seek treatment before symptoms become severe. Pay attention to changes in your breathing—particularly increasing shortness of breath with activities that previously did not cause symptoms, or breathlessness when lying flat. A persistent dry cough, chest discomfort, or reduced exercise tolerance may also indicate fluid buildup.

Some patients find it helpful to keep a symptom diary, noting when breathing difficulties occur and what activities trigger them. This information can help your healthcare team determine the optimal timing for drainage procedures.

Working with Your Healthcare Team

Regular follow-up appointments are essential for monitoring your condition and adjusting treatment as needed. Bring a list of questions to each appointment and be honest about your symptoms, even if they seem minor. Your healthcare team can only help if they know what you are experiencing.

If you have an indwelling pleural catheter, you will need regular check-ups to ensure the catheter is functioning properly and to watch for complications such as infection or catheter blockage. Do not hesitate to contact your healthcare team between appointments if you notice problems.

Staying Active

While pleural effusion can limit your activity, staying as active as possible within your limitations is important for maintaining strength and quality of life. Talk to your doctor about what level of physical activity is safe and appropriate for you. Even gentle activities like walking, stretching, or light yoga can help maintain muscle strength and improve mood.

Pulmonary rehabilitation—a supervised program of exercise and education for people with lung conditions—may be helpful for some patients. Ask your doctor if this might be appropriate for your situation.

Emotional and Psychological Support

Living with a chronic condition can be emotionally challenging. Feelings of frustration, anxiety, or sadness are normal and understandable. Consider seeking support from counselors, support groups, or mental health professionals who specialize in helping people with chronic illness.

Connecting with others who have similar experiences can also be valuable. Ask your healthcare team about support groups in your area or look for online communities where you can share experiences and learn from others.