Thoracentesis

Your lungs are wrapped in two thin, slippery layers called the pleura. Normally there are only a few teaspoons of fluid between them. When too much fluid builds up in this space, it is called a pleural effusion. It can happen on one side or both.

The fluid takes up room the lung needs to expand. A large effusion can squeeze part of the lung flat. You may feel short of breath, especially when walking or lying flat, have a dry cough or feel chest heaviness.

On ultrasound, fluid around the lung looks black. The lung floats in it as a gray, moving shape, and the diaphragm is a bright curved line below. We choose a spot where the fluid pocket is deepest, well away from the lung, liver or spleen.

Thoracentesis does two jobs. Therapeutic drainage removes fluid so you can breathe more easily. Diagnostic drainage sends a sample to the lab to find the cause. Often we do both at once. We may also draw a blood sample to compare with the fluid.

Lab tests check protein, sugar, cell counts, signs of infection and cancer cells. These tell your doctor whether the fluid is a leak caused by pressure or low protein, as in heart failure (a transudate), or a sign of inflammation, infection or cancer (an exudate).

Treating the cause, for example with heart failure medicines or antibiotics, often stops the fluid from returning. If it keeps coming back, especially with cancer, there are longer-term options.

Read more about chest PleurX catheters and pleurodesis.

1. 1
   Sitting up

   You sit on the edge of the table and lean forward, resting your arms on a padded stand. If you cannot sit, we can do it lying on your side.

2. 2
   Ultrasound and numbing

   We find the fluid with ultrasound, mark the spot on your back, clean the skin and numb it down to the pleura. You feel a sting and then pressure.

3. 3
   Draining the fluid

   A thin needle with a soft plastic tube over it goes between two ribs into the fluid. The needle comes out, leaving only the soft tube, and fluid drains into a vacuum bottle.

4. 4
   Finishing up

   We remove the tube, place skin glue or a bandage, and send samples to the lab.

As the lung re-expands, it is common to feel chest tightness or the urge to cough, usually near the end. Tell us, because it often means it is time to stop. We usually remove no more than about 1 to 1.5 liters at a time to protect the lung.

I always scan the chest right before I start, even if you had a scan yesterday, because fluid shifts. I look for the deepest pocket with a safe margin from the lung. I also watch you as much as the ultrasound: a cough or tightness tells me the lung is coming back up, and that is usually when I stop.

Fabio Komlos, MD, interventional radiologist · About Dr. Fabio Komlos

1. Right after
   Rest for a short while. Some people have a chest X-ray, especially if they have new symptoms. Many breathe more easily right away.
2. Same day
   You can eat normally and shower. Most people can drive home.
3. First 24 hours
   Avoid heavy lifting and hard exercise. Mild soreness at the site is normal.
4. Day 2 onward
   Back to your usual activities. Your doctor will call with lab results, usually within a few days.

An ice pack and acetaminophen (Tylenol) or ibuprofen usually control any soreness. Soreness should fade within a day or two.

Using ultrasound keeps thoracentesis safe. The most important risk is an air leak around the lung (pneumothorax), which happens in about 1 to 3 in 100 procedures. Most are small and need no treatment. A chest tube is rarely needed. See pneumothorax.

Other risks are uncommon: bleeding, infection, lightheadedness or fainting during the procedure, and a cough or tightness from the lung re-expanding. Rarely, removing a lot of fluid quickly causes fluid to build up inside the lung (re-expansion pulmonary edema), which is why we limit how much we drain.