What Is Paracentesis?

For some people it creeps up gradually — trousers that feel tighter week by week, a belly that looks swollen even though they haven't gained weight elsewhere, a feeling of fullness after only a few mouthfuls. Often, what's behind that is fluid collecting inside the abdomen, and paracentesis is the procedure used both to examine that fluid and to relieve it. The longer recording above, at just over 21 minutes, follows a paracentesis carried out to drain abdominal fluid, so you can see the pace and setup of the real thing rather than a quick summary.

First, the fluid itself: what ascites means

The fluid has a name — ascites — and it collects in the space around the organs inside the belly, called the peritoneal cavity. As its own description puts it, that buildup may be caused by infection, inflammation, an injury, or other conditions, and in practice it is frequently linked to long-standing liver disease; if that side of the picture is new to you, our overview of cirrhosis of the liver explains how a struggling liver can lead to fluid collecting this way. Whatever the cause, a swollen, fluid-filled abdomen can feel heavy and uncomfortable and can press upward, making deep breaths harder. Removing some of the fluid can ease that pressure — and examining it can help the team understand why it formed.

Getting ready on the day

Expect things to start with checks rather than instruments. The team will usually review your history, examine your abdomen, and often use an ultrasound scan to confirm where the fluid sits and choose a safe spot — you can see that ultrasound-guided preparation reflected in the setting of many paracentesis videos. You will typically be positioned lying back, propped up a little, with the skin over the chosen area cleaned carefully. A local anaesthetic is commonly used to numb the small area where the needle will go, so what most people feel is pressure rather than sharp pain. If anything about the plan is unclear, this preparation stage is the moment to ask — the team would much rather explain than have you lie there wondering.

While the fluid drains

Once the area is numb, a fine needle or thin tube is passed through the abdominal wall into the fluid, and the fluid drains out into a collection container. It tends to be a slow, unhurried stage rather than a dramatic one — the site's shorter recording, "Abdominal paracentesis", at just under five minutes, shows the same drainage principle in a more compact form. The team keeps an eye on you throughout, and samples of the fluid are normally sent to the laboratory, because what is in that fluid — cells, signs of infection, protein patterns — often points toward its cause. When enough fluid has been removed, the needle or tube comes out and a small dressing covers the spot. Afterwards you will usually rest for a while and have routine observations checked before going home or back to the ward, and the team will tell you what to watch for and who to contact once you leave.

Frequently Asked Questions

Is paracentesis painful?
The area is usually numbed with local anaesthetic first, so most people describe pressure or a pushing sensation rather than pain. Tell the team if you feel discomfort during the procedure — they can pause and help.

Why is the fluid sent for testing?
Because the fluid itself holds clues. Laboratory tests on the sample can look for infection, count cells, and measure proteins, all of which help the team work out why fluid collected in the first place.

Does the fluid come back afterwards?
It can. Paracentesis removes the fluid that is there on the day, but if the underlying cause continues, fluid may gradually collect again — which is why follow-up and treatment of the cause itself matter, and why some people need the procedure more than once.

What should I watch for after paracentesis?
Your team will give you specific advice, but in general, contact them if you notice fluid leaking persistently from the puncture spot, increasing pain, redness, or fever after the procedure.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Educational only — this article is general information about paracentesis, not medical advice and not a diagnosis. If you have abdominal swelling or have been advised to have this procedure, talk to your treating team about your own situation.