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Thoracentesis (pleural tap)
Category: Lung & Breathing Tests · All lung & breathing tests
What it is
Thoracentesis removes fluid that has collected between the lung and chest wall (a pleural effusion) using a needle or small catheter, usually guided by ultrasound. The fluid is tested to find its cause, and removing larger volumes relieves breathlessness.
Why it is done
It is done to diagnose the cause of a pleural effusion (infection, heart failure, cancer, inflammation) and to relieve breathlessness from a large effusion.
How to prepare
An ultrasound scan at the bedside marks a safe pocket of fluid. Blood tests including clotting are checked; tell the team about blood thinners and allergies. No fasting is normally needed for a tap under local anaesthetic.
What happens during the procedure
You sit leaning forward over a table (or lie on your side). After numbing the skin and deeper tissues, the needle enters the fluid space between the ribs; samples are taken into bottles for the laboratory, and larger amounts may be drained through a small catheter to a bag. It takes about 15 to 30 minutes.
Afterwards — recovery & results
A chest X-ray or ultrasound check may follow. Breathlessness usually improves promptly. You can go home the same day in most cases once observations are stable. Fluid results take several days; the clinic will explain the cause and the plan.
Risks & considerations
Risks include pain, bleeding, infection, the lung not fully re-expanding, and air leaking into the pleural space (pneumothorax) — uncommon with ultrasound guidance, occasionally needing a chest drain. Report increasing breathlessness or chest pain afterwards.
Watch: Thoracentesis (pleural tap) videos
Real procedure videos from the MedicalVideos.com library. Some clinical footage is graphic — that is the nature of a medical video library.
Related guides on MedicalVideos.com
Frequently asked questions
Why did the fluid build up?
The fluid tests, together with scans and your history, distinguish the causes — heart failure, infection, inflammation, low protein, or cancer among them. The tap is the key diagnostic step.
Will the fluid come back?
It depends on the cause. Treating heart failure or infection may resolve it; recurrent effusions have options such as pleurodesis or a long-term tunnelled drain, which your team would discuss.
Related procedures — Lung & Breathing Tests
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