thoracentesis
Meaning of thoracentesis: One needle answers two questions at once, easing the pressure squeezing the lung and supplying the sample that explains why fluid gathered.
Definition of thoracentesis
Thoracentesis is the removal of fluid from the pleural space, the narrow gap between the lung and the chest wall, using a needle passed between two ribs. That space normally holds only a thin film of lubricating fluid. When disease causes a larger collection to build, the fluid can be drawn off to analyze it, to ease breathing, or to do both in one sitting.
What does the fluid itself reveal?
A great deal, which is why even a small sample is worth taking. The first question asked of it is whether the fluid leaked out because of pressure and low protein in the blood, or because the lining itself is diseased and leaking. The first pattern, thin and low in protein, points toward heart failure, liver disease or kidney disease, none of them a problem of the chest at all. The second, rich in protein and cells, points toward infection, cancer, a clot in the lung or inflammation of the lining. Appearance narrows it further: straw colored and clear is common, cloudy or frankly purulent means infected, uniformly bloody raises the possibility of cancer or injury, and milky suggests lymphatic fluid has escaped into the space.
How is the procedure done?
| Step | Why it is done that way |
|---|---|
| Sitting up, leaning forward on a table | Fluid settles at the base, away from the lung |
| Ultrasound to mark the spot | Confirms fluid rather than solid tissue and shows how deep it lies |
| Local anesthetic to the skin and ribs | The lining of the chest wall is what hurts, not the lung |
| Needle entering just above a rib | The artery, vein and nerve run in a groove beneath each rib |
What can go wrong?
The best known complication is a collapsed lung, which happens if air enters the pleural cavity or the needle nicks the lung surface. Ultrasound guidance has made this considerably less frequent than it once was. Bleeding into the space can follow injury to a vessel in the chest wall, and infection can be introduced through the puncture, though both are uncommon. A different problem arises when a very large volume is drained at once: a lung compressed for a long period can develop fluid in its own tissue as it re-expands, which is why removal is usually limited in a single session and stopped if chest tightness or coughing develops.
Also known as
Used in a sentence
Thoracentesis was performed to relieve the patient's shortness of breath caused by a large pleural effusion.
Good to know
A collapsed lung is the complication most closely watched for after thoracentesis, since air can enter the pleural space during the procedure even when it is performed carefully with ultrasound guidance.
Word origin
Where “thoracentesis” comes from
Formed from thorac-, Greek for chest, and -centesis, from kentesis, meaning a puncturing.