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 difficulty 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).
• Have had bleeding problems or are taking blood thinners, such as aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), or warfarin (Coumadin).
• 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. 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, 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.