Test Overview

Paracentesis is a procedure to take out
fluid that has collected in the belly (peritoneal fluid). 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
long, 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 in people with cancer or

Why It Is Done

Paracentesis may be done to:

  • Find the cause of fluid buildup in the
  • Diagnose an infection in the peritoneal
  • Check for certain types of cancer, such as liver
  • 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.
  • Check for damage after a belly injury.

How To Prepare

Before you have paracentesis done, tell
your doctor if you:

  • Are taking any medicine.
  • Are
    allergic to any medicines, including numbing medicines (anesthetics).
  • Take a blood thinner, or if you have had bleeding problems.
  • Are or might be pregnant.

Other blood tests may be done before a paracentesis to make
sure that you do not have any bleeding or clotting problems. You will empty
your bladder before the procedure.

You may be asked to sign a consent form that says you understand the risks of the test and agree to have it done.

Talk to your doctor about any concerns you have regarding the
need for the test, its risks, how it will be done, or what the results will
mean. To help you understand the importance of this test, fill out the
medical test information form (What is a PDF document?).

How It Is 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.

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 your
belly. Once the area is numb, your doctor will gently and slowly put the
paracentesis needle in where the extra fluid is likely to be. Your doctor will
be careful to not poke any blood vessels or the intestines. 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 a large amount of fluid is present, 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, you may be given
fluids through an
intravenous line (IV) in a vein in your arm. This
fluid is needed to prevent low blood pressure or
shock. 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.

Paracentesis takes about 20 to 30 minutes. It will take longer if a large
amount of fluid is taken out. You can do your normal activities after the test
unless your doctor tells you not to.

How It Feels

You may feel a brief, sharp sting when
the numbing medicine is given. When the paracentesis needle is put into your
belly, you may feel a temporary sharp pain or pressure.

You may
feel dizzy or lightheaded if a large amount of fluid is taken out. Tell your
doctor if you do not feel well during the test.

After the
procedure, you may have some clear fluid draining from the site, especially if
a large amount of fluid was taken out. The drainage will get less in 1 to 2
days. A small gauze pad and bandage may be needed. Ask your doctor how much
drainage to expect.


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

If cancer cells are present in the peritoneal fluid, there
is a small chance that the cancer cells may be spread 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. This could lead to shock. If you go
into shock, IV fluids or medicines, or both, may be given to help return your
blood pressure to normal. There is also a small chance that removing the
peritoneal fluid may affect how your kidneys work. If this is a concern, IV
fluids may be given during the paracentesis.

After the test

Call your doctor immediately if you

  • A fever higher than
    100°F (38°C).
  • Severe belly pain.
  • More redness or
    tenderness in your belly.
  • Blood in your urine.
  • Bleeding
    or a lot of drainage from the site.


Paracentesis is a procedure to take out
fluid that has collected in the belly (peritoneal fluid). This fluid buildup is called
ascites. 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.


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,
    nephrotic syndrome, or
    pancreatitis. Low protein levels in the fluid may mean
    cirrhosis or clots in veins of the liver are
  • 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
    enzyme LDH may mean infection or cancer is
  • 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 Affects the Test

Reasons you may not be able to
have the test or why the results may not be helpful include:

  • Using blood thinners (anticoagulants) or aspirin, which can increase the chance of bleeding.
  • Having blood, bile, urine, or
    feces in the fluid sample.
  • Not being able to stay still during the
  • Being
  • Having scars inside the belly
    (adhesions) from any belly surgery in the past.

What To Think About

Sometimes doctors use fluids put
into the belly to check for injuries. This is called peritoneal lavage. During
this procedure, a doctor uses a paracentesis needle to put a salt (saline)
fluid into the belly. The fluid is then taken out through the same needle. If
the fluid that comes out is bloody, the bleeding is probably being caused by an
injury inside the belly.


Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.


ByHealthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD – Internal Medicine
Adam Husney, MD – Family Medicine
Specialist Medical Reviewer Jerome B. Simon, MD, FRCPC, FACP – Gastroenterology

Current as ofMay 5, 2017