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Paracentesis (Taking a Sample of Fluid From the Abdomen)

Critical Care

Paracentesis is performed to figure out what may be causing fluid to build up inside the abdomen (called ascites). Some diseases, such as liver cirrhosis (damage of the liver), cancer and certain infections may cause a build up of fluid inside the abdomen. The fluid can often be seen with ultrasound or other x-ray tests. Paracentesis involves placing a needle and/or thin, hollow plastic tube into the abdomen to get some of the fluid for testing.

Common reasons for its use and benefits:

When the cause of the build up of fluid is not known, getting a sample of the fluid can help in reaching an answer. The most common reasons for doing a paracentesis are:

  • New-onset ascites - In any patient with the recent build up of fluid in the abdomen with no obvious cause.
  • Infection - If infection is suspected, paracentesis may be done to help make a diagnosis.
  • Cancer - Some cancers can spread and cause a build up of fluid in the abdomen. Paracentesis may be the simplest way to get a sample of cancer cells to make a diagnosis instead of doing a surgical biopsy.
  • Comfort - A large build up of fluid in the abdomen can be uncomfortable and interfere with being able to breathe deeply. Removing some fluid may decrease discomfort.


Some of the risks of paracentesis include:

  • Pain during placement - Discomfort can result from the needle stick at the time it is inserted. Doctors try to lessen the pain with a local numbing medicine (anesthetic like novocaine). The discomfort is usually mild and goes away once the needle or catheter is removed.
  • Bleeding - While the needle is inserted through the skin, a blood vessel may be accidentally nicked. The bleeding is usually minor and stops on its own. The bleeding may cause a bruise of the abdominal wall. Rarely it can cause internal bleeding that might require surgery.
  • Bowel injury or perforation - The needle may, rarely, puncture the bowel. The small hole often seals over quickly. If the hole does not seal over, the bowel contents can ooze out and cause a serious infection, which may require surgery to repair.