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Paracentesis is a procedure to remove fluid that has accumulated in the abdominal cavity (peritoneal fluid), a condition called ascites . Ascites may be caused by infection, inflammation, abdominal injury, or other conditions, such as cirrhosis or cancer. The fluid is removed using a needle inserted through the abdominal wall and sent to a lab for analysis to determine the cause of the fluid buildup. Paracentesis also may be done to drain the fluid as a comfort measure in people with cancer or chronic cirrhosis.

The peritoneum is the lining of the abdominal cavity. It supports the organs in the abdomen and helps protect them from infection. The inside surface of the peritoneum produces a very small amount of peritoneal fluid that allows the organs in the abdomen to slide against the peritoneum and each other.

Why It Is Done

Paracentesis may be done to:

  • Determine the cause of fluid buildup in the abdominal cavity (ascites).

  • Diagnose infection in the peritoneal fluid.

  • Detect 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 the function of the kidneys or the intestines (bowel).

  • Evaluate abdominal injury.


How To Prepare

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

  • Are taking any medication.

  • Are allergic to any medications, including anesthetics.

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

  • Are or might be pregnant.

Blood tests may be done before a paracentesis to make sure that you do not have any bleeding or clotting problems. Empty your bladder before the procedure because a full bladder can interfere with performing the test.

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 indicate.

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 removed during the procedure, you may lie on your back with your head slightly raised. People who have less fluid removed may be allowed to sit up. The site where your doctor will insert the needle is cleaned with an antiseptic solution and draped with sterile towels.

Your doctor injects a local anesthetic into your abdominal wall to numb the area where the paracentesis needle will be inserted. Once the area is numb, your doctor will gradually insert the paracentesis needle where the fluid is likely to be. If your test is done in the X-ray department, an ultrasound may be used to confirm the location of fluid in your abdomen.

As the paracentesis needle is gradually advanced through the abdominal wall, your doctor will pull back on the syringe to ensure that neither a blood vessel nor the intestine has been punctured. When the abdominal cavity is entered, fluid will flow into the syringe. If a large amount of fluid is present, the paracentesis needle may be connected by a small tube to a vacuum bottle; fluid will then be drained through the needle into the vacuum bottle.

Generally, up to 4 L of fluid is removed. If your doctor needs to remove a larger amount of fluid, intravenous line (IV) fluids may be given through a vein in your arm to prevent low blood pressure or shock. It is important that you remain completely still throughout the procedure, unless you are asked to change positions to help move the fluid.

Once the desired amount of fluid has been removed, the needle is withdrawn and a bandage is placed over the puncture site. After the test, your pulse, blood pressure, and temperature are usually monitored. You may be weighed and the distance around your abdomen may be measured before and after the test.

This procedure usually takes about 20 to 30 minutes. It will take longer if a large amount of fluid is being removed. When it is over, you may resume normal activities unless your doctor tells you otherwise.

How It Feels

You may feel a brief, sharp stinging or burning pain when the local anesthetic is injected. When the paracentesis needle is inserted into the abdominal wall, you may again feel a temporary sharp pain or pressure, similar to having your blood drawn.

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

After the procedure, you may notice some clear fluid draining from the needle site, especially if a large amount of fluid was removed from your abdominal cavity. The drainage should subside within 1 to 2 days. A small gauze pad covered by a bandage generally helps absorb the fluid. Ask your doctor how much drainage to expect.


There is a very slight chance that the needle used to withdraw the fluid might puncture the bladder, bowel, or a blood vessel within the abdomen.

If cancer cells are present in the peritoneal fluid, there is a slight risk that the needle used to withdraw the fluid might spread the cancer cells within the abdominal cavity.

If a large amount of fluid is removed, there is a small risk that your blood pressure could drop to a low level, leading to shock. If this occurs, intravenous (IV) fluids or medications, or both, may be given to help return your blood pressure to normal. There is also a small risk that the removal of fluid may decrease your kidney function. If this is a concern, IV fluids may be given during the paracentesis.

After the test

Contact your doctor immediately if you experience:
an 100 F. Severe abdominal pain. Increasing abdominal redness or tenderness. Blood in your urine. Bleeding or excessive drainage from the site where the paracentesis needle was inserted.


Paracentesis is a procedure to remove excess fluid that has accumulated in the abdominal cavity (peritoneal fluid), a condition called ascites . Fluid removed from your abdomen will be sent to a lab to be examined under a microscope. Preliminary results will be available within a few hours.

What Affects the Test

Factors that can interfere with your test and the accuracy of the results include:Use medications and aspirin, which can increase the risk of bleeding. A fluid sample contaminated with blood, bile, urine, or feces. Inability to remain still during the test.Obesity or abdominal adhesions from a previous abdominal surgery.

What To Think About

A paracentesis is often done when signs or symptoms of peritonitis develop. Pregnant women may not have this test done because there is a risk that the needle used to withdraw abdominal fluid could puncture the uterus and injure the baby (fetus).

Abdominal injuries and pain are sometimes evaluated using peritoneal lavage. During this procedure, a doctor uses a needle to inject a saline solution into the abdominal cavity. The fluid is then withdrawn through the same needle. If the fluid withdrawn is bloody, the bleeding is probably being caused by an injury inside the abdomen.

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