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 cirrhosis.
Why It Is 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, such as liver 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.
- 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 belly.
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 have:
- 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.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
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.
Current as of: November 7, 2018
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Jerome B. Simon MD, FRCPC, FACP - Gastroenterology