What is paracentesis?

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Paracentesis: Overview

Paracentesis is a procedure to take out fluid that has collected in the belly (peritoneal fluid) outside the intestines. This fluid buildup is called ascites. Ascites may be caused by infection, inflammation, an injury, or other conditions, such as cirrhosis or cancer. The fluid is taken out using a thin needle put through the belly. The fluid is sent to a lab and studied to find the cause of the fluid buildup. Paracentesis also may be done to take the fluid out to relieve belly pressure or pain.


Paracentesis is a procedure in which a needle is inserted through the abdominal wall to remove fluid that has built up in the abdominal cavity (ascites). It may be used as a test (diagnostic paracentesis) or as a treatment (therapeutic paracentesis).

Paracentesis may be done to:

  • Collect a fluid sample from the abdominal cavity to help find out the cause of ascites (diagnostic).
  • Diagnose infection in the ascitic fluid (diagnostic).
  • Remove a large amount of fluid from the abdominal cavity when the fluid is causing discomfort or affecting the function of the kidneys or intestines (therapeutic).

How long does a paracentesis take?

The procedure may take from a few minutes to 30 minutes or more.

How do you prepare for a paracentesis?

If you take a medicine that prevents blood clots, your doctor may tell you to stop taking it before your procedure. Or your doctor may tell you to keep taking it. (These medicines include aspirin and other blood thinners.) Make sure that you understand exactly what your doctor wants you to do.

Other blood tests may be done before a paracentesis to make sure that you don't have any bleeding or clotting problems.

What happens after a paracentesis?

You can do your normal activities after the procedure, unless your doctor tells you not to.

After the procedure, you may have some clear fluid draining from the site, especially if a large amount of fluid was taken out. There will be less drainage in 1 to 2 days. Ask your doctor how much drainage to expect.

A small gauze pad and bandage may be needed. You may need to change the bandage.

If your doctor thinks that testing the fluid can help find out the cause of a problem, your doctor will send it to a lab.

If fluid builds up in your belly again, your doctor may repeat this procedure.

What are the risks of paracentesis?

There is a very small chance that the paracentesis needle may injure the bladder, bowel, or a blood vessel in the belly.

There is a very small chance of causing an infection in the belly.

If a large amount of fluid is removed, there is a small chance that your blood pressure could drop to a low level. If this is a concern, I.V. fluids, medicines, or both may be given during the paracentesis.

What do the results of a paracentesis mean?

The fluid taken from your belly will be sent to a lab to be studied and looked at under a microscope. Results will be ready in a few hours.

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No infection, cancer, or abnormal values are found.


Several tests may be done on the fluid.

  • Cell counts. A high number of white blood cells (WBCs) in the fluid may mean inflammation, infection (peritonitis), or cancer is present. A high WBC count and a high count of WBCs called polymorphonuclear leukocytes (PMNs) may mean there is an infection inside the belly called spontaneous bacterial peritonitis (SBP).
  • Serum-ascites albumin gradient (SAAG). The SAAG compares the level of protein in the fluid to the level of protein in the blood. High protein levels in the fluid may mean cancer, tuberculosis, nephrotic syndrome, or pancreatitis. Low protein levels in the fluid may mean cirrhosis or clots in veins of the liver are present.
  • Culture. A culture can be done on the fluid to see whether bacteria or other infectious organisms are present.
  • Lactate dehydrogenase (LDH). High levels of the enzyme LDH may mean infection or cancer is present.
  • Cytology. Abnormal cells in the fluid may mean cancer is present.
  • Amylase. High levels of amylase may mean pancreatitis or that there is a hole in the intestine.
  • Glucose. Low levels of glucose may mean infection.

What is paracentesis?

Paracentesis (say "pair-uh-sen-TEE-sus") is a procedure that removes fluid from the belly. The buildup of fluid may be caused by infection, inflammation, an injury, or other problems.

Swelling from too much fluid may cause pain or trouble breathing. The doctor will remove the extra fluid with a needle attached to a tube.

Paracentesis: When to call

Call 911 anytime you think you may need emergency care. For example, call if:

  • You passed out (lost consciousness).

Call your doctor now or seek immediate medical care if:

  • You are dizzy or lightheaded, or you feel like you may faint.
  • You have new or worse belly pain.
  • You have symptoms of infection from the paracentesis site, such as:
    • Increased pain, swelling, warmth, or redness.
    • Red streaks leading from the area.
    • Pus draining from the area.
    • A fever.

Watch closely for changes in your health, and be sure to contact your doctor if:

  • Fluid builds up in your belly again.
  • You do not get better as expected.

How is a paracentesis done?

This procedure may be done in your doctor's office, an emergency room, or the X-ray department of a hospital, or at your bedside in the hospital.

You will empty your bladder before the procedure.

If a large amount of fluid is going to be taken out during the procedure, you may lie on your back with your head raised. People who have less fluid taken out may sit up. The site where your doctor will put the needle is cleaned with a special soap and draped with sterile towels.

Your doctor puts a numbing medicine into the skin of your belly. When the area is numb, your doctor will gently and slowly put the paracentesis needle in where the extra fluid is. If your test is done in the X-ray department, an ultrasound may be used to show where the fluid is in your belly.

If fluid is being removed for testing, your doctor will use a syringe to take a sample of fluid.

If there's a large amount of fluid, the paracentesis needle may be hooked by a small tube to a vacuum bottle for the fluid to drain into it. Generally, up to 4 L (1 gal) of fluid is taken out.

If your doctor needs to remove a larger amount of fluid, there is a small chance that your blood pressure could drop to a low level. You may be given fluids through an intravenous line (I.V.) in a vein in your arm. It is important that you lie completely still during the procedure, unless you are asked to change positions to help drain the fluid.

When the fluid has drained, the needle is taken out and a bandage is placed over the site. After the test, your pulse, blood pressure, and temperature are watched for about an hour. You may be weighed and the distance around your belly may be measured before and after the test.

Why is paracentesis done?

Paracentesis may be done to:

  • Find the cause of fluid buildup in the belly.
  • Diagnose an infection in the peritoneal fluid.
  • Check for certain types of cancer.
  • Remove a large amount of fluid that is causing pain or trouble breathing or that is affecting how the kidneys or the intestines (bowel) are working.

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