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A paracentesis is a procedure in which a hollow needle or tube is inserted through the skin and into the abdominal cavity or peritoneum. The peritoneum is the membrane that lines the walls of the abdomen and pelvis (parietal peritoneum), and covers most of the abdominal organs (visceral peritoneum). A paracentesis may also be called an abdominal tap.

Why a paracentesis is done

A paracentesis is done to:

  • collect fluid for examination under a microscope
  • remove excess fluid from the abdominal cavity or peritoneum (ascites)
    • The fluid may be examined to help find the cause of the ascites.
    • Removing extra fluid helps relieve abdominal swelling.

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How a paracentesis is done

A paracentesis can often be done in a hospital or outpatient clinic.

  • The person often lays down on a bed with the head of the bed elevated for the procedure.
  • A local anesthetic is used to numb the area where the paracentesis needle will be inserted.
  • The doctor then inserts a thin, hollow needle or plastic tube (catheter) into the abdominal cavity. Once the needle is inserted, excess fluid is removed.
  • Sometimes an ultrasound is done to help the doctor find the right place to insert the needle or tube for a paracentesis.
  • A small amount of fluid is sent to the laboratory so that it can be examined under a microscope. More fluid is removed if ascites is present.
  • A paracentesis usually takes 20–30 minutes. It may take a little longer if there is a lot of fluid in the abdomen.
  • The needle or tube is removed once the fluid is drained.
  • If doctors think the fluid will build up again, they may use a tunnelled peritoneal drainage catheter. One end of this type of catheter stays in place in the body and the other end is attached to a bottle or container outside of the body. The person can drain the fluid at home so they don’t need to keep going back to the hospital.
  • A small bandage is placed on the site where the needle or tube was inserted.

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Potential side effects

The risks from a paracentesis are:

  • discomfort or pain at the insertion site
  • dizziness or lightheadedness (if a large amount of fluid is removed)
  • low blood pressure or shock (if a large amount of fluid is removed)
  • bruising or bleeding
  • infection
  • potential bowel injury

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What the results mean

Excess fluid in the abdomen can be caused by:

  • injury to the abdomen
  • infection of the peritoneum (peritonitis)
  • scarring (cirrhosis) of the liver tissue
  • liver failure
  • cancer

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What happens if a change or abnormality is found

The doctor will decide whether further tests, procedures, follow-up care or additional treatment is needed.

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