What Is Thoracentesis?

The lungs are protected by a double-layer membrane called the pleura: an outer visceral pleura and an inner parietal pleura. Between these layers is a small pleural space that contains a lubricating fluid to reduce friction when you breathe. In some cases, this pleural space can accumulate excess fluid, leading to a condition called pleural effusion.

"We normally have a small amount of fluid between the lungs and the rib cage," said Khaled Alshabani, MD, a board-certified pulmonologist and member of the Thoracic Oncology Multidisciplinary Team at Karmanos Cancer Institute. "When the fluid amount is abnormally increased, it often leads to difficulty breathing and chest discomfort."

If this happens to you, your doctor may recommend a procedure to drain the excess fluid.

"Thoracentesis is a minimally invasive procedure done with local anesthesia that involves placing a small catheter through the chest wall into the pleural space around the lung, usually with ultrasound guidance," said George Chaux, MD, a board-certified interventional pulmonologist and medical director of Interventional Pulmonary at Providence Saint John’s Health Center in Santa Monica, California.

You may need a thoracentesis if there is "abnormal fluid collection in the pleural space that exists between the lung and the chest wall," explained Dr. Chaux.

Thoracentesis has both diagnostic and therapeutic purposes. It can help diagnose the cause of pleural effusion, including lung cancer, and also provide relief from symptoms associated with excess fluid in the chest.

A pleural effusion is a buildup of excess fluid in the pleural space, the area between the lungs and the chest wall. This can occur from trauma, infections, congestive heart failure, or cancer.

"Thoracentesis may become necessary for someone with lung cancer when we are diagnosing the type of fluid to determine whether the pleural effusion is cancer-related (malignant) or due to other causes, such as infection or heart failure," said Amina Pervaiz, MD, a board-certified pulmonologist at Karmanos Cancer Institute.

People with lung cancer can develop a pleural effusion when a tumor blocks the flow of fluid from the lung or when treatment affects the normal drainage of fluid. Cancer can also spread to the pleural space, which doctors refer to as a malignant pleural effusion (MPE).

Breast, ovarian, and lymphoma cancers can also cause pleural effusions. In some cases, a pleural effusion may be the first sign of cancer or a recurrence in people with a history of cancer. However, the procedure may help diagnose the cancer and relieve the symptoms.

Most pleural effusions are treatable. However, the prognosis of a pleural effusion depends on its underlying cause. Those who develop the condition due to treatment, infection, or other conditions may have a better outlook than those with MPE.

Research published in Frontiers in Medicine in 2022 looked at 508 hospitalized patients with pleural effusions of varying causes, including cancer. The study found that those with MPEs had the worst long-term survival rates, with a one-year mortality rate of around 74%.

Another study, published in 2019 in Reviews on Recent Clinical Trials, found an average survival rate of 4 to 9 months for people with MPEs. Mortality rates were lower in those with metastatic disease without a malignant pleural effusion.

Before the procedure, your doctor will discuss what to expect and give specific instructions. You may be asked to stop taking certain medications a few days before the procedure, such as blood thinners. You may not be able to eat or drink for a few hours before.

In addition, the doctor may order imaging tests, such as a chest X-ray or CT scan, to determine the location and amount of fluid. They may also perform blood tests to check your clotting factors and overall health.

It's important to tell your provider if you have allergies or are taking any medications or over-the-counter supplements. You should also disclose any previous bleeding disorders or previous issues with anesthesia.

If you're having an outpatient procedure, you will need a ride home afterward due to the effects of the anesthesia. You may also be advised to rest and avoid strenuous activity for a day or two afterward. In some cases, you may have to stay in the hospital overnight.

"The procedure takes about 30 minutes to complete," said Dr. Alshabani. Some of that time is spent getting you into the correct position and preparing the needle insertion site. Your doctor may use ultrasound or CT to visualize the fluid before the procedure.

Thoracentesis Position

You will sit upright with your body leaning slightly forward and arms resting on a table in front of you, said Dr. Pervaiz. This helps open up the spaces between your ribs and allows your doctor better access to the pleural space.

In some cases, your doctor will ask you to lie on the side of the affected lung, with the arm above your head. This can also help open up the space between the ribs.

Draining Fluid From the Lungs

1. Once you're in position, your doctor will clean the area with an antiseptic and inject local anesthesia to numb the area where they will perform the procedure. They may also give you a sedative to help you relax.

2. After the area is numb, your provider inserts the needle or catheter into the chest between the rib bones. They may use imaging methods, such as ultrasound or CT, to guide the needle into the correct location.

3. The fluid is drained through the needle or catheter into a collection bottle. You may be asked to change your breathing pattern during the procedure to help with fluid flow.

4. The amount of fluid removed depends on your condition and symptoms, but it typically ranges from 500 milliliters to over 1 liter. If you have a lot of fluid, your doctor may drain it in stages over a few days to reduce discomfort and potential complications. This requires an inpatient hospital stay.

5. Once the procedure is complete, your doctor will remove the needle or catheter and cover the site with a bandage or dressing. They may also request one or more follow-up chest X-rays to ensure all the fluid has been removed and there are no complications.

A nurse will monitor you for signs of complications. You may experience mild discomfort or soreness at the needle insertion site or develop a bruise within a few days of the procedure.

Your doctor will instruct you to:

• Rest for the remainder of the day and avoid strenuous activity for a few days

• Avoid blood-thinning medications or supplements for a few days

• Drink plenty of fluids to replace any lost during the procedure

• Contact your doctor if you experience any signs of infection, such as fever or chills, redness or swelling at the needle site, or difficulty breathing

Depending on the reason for the procedure, you may need another thoracentesis in the future. Your doctor will discuss this with you and any other follow-up care needed.

It's important to weigh the potential risks and benefits before opting for a thoracentesis.

Risks

• Pain or discomfort at the site of the needle insertion

• Pneumothorax (collapsed lung) due to accidental puncture of the lung

• Bleeding from the puncture site or within the chest cavity

• Infection at the puncture site or within the pleural space

• Liver or spleen injury, especially when done on the left side

• Shortness of breath or feeling faint during or after the procedure

• Re-expansion pulmonary edema can occur if a large amount of fluid is removed quickly (rare)

Potential Benefits

• Quick relief from your symptoms, such as shortness of breath, chest pain, or coughing

• Improved breathing and lung function

• Diagnosis of the underlying cause of your pleural effusion

• Ability to test the fluid for cancerous cells or other abnormalities

• Improved ability to treat your condition and manage symptoms

Follow your doctor's instructions for post-op care to reduce the risk of complications and promote healing. They may recommend that you:

• Take pain medication as prescribed

• Avoid strenuous activity for a few days

• Keep the bandage on until your doctor advises removing it

• Keep the needle insertion site clean and dry

• Monitor the insertion site for signs of infection, such as redness, swelling, or drainage

• Follow up with your doctor for repeat chest X-rays or other tests

• Contact your doctor if you experience any signs of infection or other complications.

The fluid sample is sent to a laboratory for testing. "Results from the fluid analysis can help guide treatment decisions for underlying conditions such as cancer or infection," Dr. Pervaiz said. Your results give insights into the following:

• Color, clarity, and volume of the fluid

• Cell counts and types present in the fluid sample

• Protein and glucose levels in the fluid

• pH level of the fluid

• Presence of bacteria, cancer cells, or other abnormal cells

Your doctor will discuss the results with you and may order additional tests if needed.

Thoracentesis is a relatively safe procedure that helps drain fluid from the lungs. It can quickly relieve symptoms and help diagnose underlying conditions, but it is not without potential risks. Your doctor will discuss these with you and answer any questions or concerns you may have before the procedure.