Pleural fluid analysis

Pleural fluid analysis


A diagnostic thoracentesis involves the removal and lab analysis of pleural fluid, a liquid the body produces to lubricate the thin tissue that surrounds the lungs. Therapeutic thoracentesis may help to relieve discomfort from shortness of breath because of a pleural effusion, a condition caused by excess pleural fluid.

In general, pleural fluid is classified as exudate (seen in inflammatory, cancerous, or infectious conditions) or transudate (fluid that has leaked from blood or lymph vessels for various reasons, such as congestive heart failure). Pleural fluid analysis may help to confirm or rule out infections or diseases such as cancer, congestive heart failure, liver failure or pulmonary hypertension (high pressure in the lungs' blood vessels).

Other related procedures that may be used to diagnose problems with the lungs and respiratory tract include bronchoscopy, computed tomography (CT scan) or magnetic resonance imaging (MRI) of the chest, chest X-ray, chest ultrasound, and oximetry. Please see these procedures for additional information.


A thoracentesis may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.

Generally, a thoracentesis follows this process:

  1. You will be asked to remove any clothing, jewelry, or other objects that may interfere with the procedure.

  2. If you are asked to remove clothing, you will be given a gown to wear.

  3. Your vital signs (heart rate, blood pressure, breathing rate, and oxygen level) may be monitored before and during the procedure.

  4. You may receive supplemental oxygen as needed, through a face mask or nasal cannula (tube).

  5. You will be placed in a sitting position with your arms raised and resting on an overbed table. This position aids in spreading out the spaces between the ribs for needle insertion. If you are unable to sit, you may be placed in a side-lying position on the edge of the bed on your unaffected side.

  6. You may be asked during the procedure to restrain from coughing, deep breathing or moving.

  7. The skin at the puncture site will be cleansed with an antiseptic solution.

  8. You will receive a local anesthetic at the site where the thoracentesis is to be performed. You may experience a brief stinging sensation at the site of the anesthetic injection.

  9. When the area is numb, the doctor will insert a needle between the ribs in your back. You may experience some pressure at the site where the needle is inserted.

  10. Once the doctor has entered the pleural space with the needle, fluid will slowly be withdrawn.

  11. If a pleural fluid analysis is to be done, several lab tubes will be filled with fluid and sent to the lab.

  12. If there is a large amount of pleural fluid, the doctor may attach tubing to the needle to allow the fluid to drain into a bottle or other type of drainage system. In some cases, the doctor may choose to leave the tubing attached for a longer period of time, such as a day or two. In this case, you will be admitted to the hospital until the tubing is removed.

  13. When the fluid has been removed, the needle will be removed.

  14. A sterile bandage or dressing will be applied.

After the procedure, you will be monitored until your blood pressure, pulse and breathing are stable. The dressing over the puncture site will be monitored for bleeding or other drainage and you may receive a chest X-ray. If the procedure was bedside, you will remain in your hospital room. You will be discharged for an outpatient thoracentesis unless your doctor decides otherwise.

When the recovery period is over, you may resume your usual diet and activities unless your doctor advises you differently. Notify your doctor of any:

  • Fever and/or chills

  • Redness, swelling, or bleeding or other drainage from the puncture site

  • Difficulty breathing

Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.


Thoracentesis may be performed for diagnostic and/or therapeutic reasons. The diagnostic use of a thoracentesis involves pleural fluid analysis to distinguish between exudate and transudate.This analysis aids in determining the cause of the abnormality, which may include:

  • Infections (viral, fungal, or bacterial)

  • Cancer

  • Systemic lupus erythematosus is an autoimmune disease in which the body attacks its own tissues and can affect every organ system in the body.

  • Pancreatitis is inflammation of the pancreas.

  • Pulmonary embolism, which is a clot in the lung that causes lung tissue necrosis (death of lung tissue)

  • Empyema is a collection of pus in the pleural space

  • Congestive heart failure

  • Tuberculosis

For an ambulance, please call:

(833) 259-CEMS (2367)

(888) 321-DOCS

Make an appointment with a Northwell doctor.

Patient tools

  • Access patient portals
  • The FollowMyHealth™ Patient Portal allows you to manage your health information online.

  • Get medical records
  • Health Information Management Offices can help patients access copies of medical records.

  • Preregister online
  • Preregistration is available for Lenox Hill Hospital maternity and surgery patients.