Abdominal tap - paracentesis

Alternative names
Peritoneal tap; Paracentesis


The abdomen usually contains a small amount of fluid. In certain conditions, fluid can accumulate in the abdomen. The abdominal tap is a procedure in which a needle is inserted through the abdominal wall into the peritoneal cavity to obtain a sample of any fluid that is present. The sample is then sent to the laboratory for analysis.

How the test is performed

This test may be done in an office setting, in a treatment room, or in a hospital.

The puncture site will be cleansed and shaved, if necessary. You then receive a local anesthetic.

The tap needle is inserted 1 to 2 inches into the abdomen. Sometimes a small incision is made to help insert the needle.

The sample of fluid is then withdrawn into a syringe. The needle is removed, and a dressing is applied to the puncture site. If an incision was made, one or two stitches may be used to close it.

How to prepare for the test

Inform your health care provider if you have any allergies to medications or anesthetic, are taking any medications (including herbal remedies), have any bleeding problems, or might be pregnant.

Infants and children:

The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

How the test will feel

You may feel a stinging sensation from the anesthetic and/or pressure as the needle is inserted.

If a large amount of fluid is withdrawn, you may experience dizziness or lightheadedness. Tell the health care provider if you feel dizzy.

Why the test is performed
Laboratory analysis of the withdrawn fluid will help determine why fluid is present in the abdomen. An abdominal tap is frequently performed to check for internal bleeding.

Normal Values

There is little or no fluid in the abdomen.

What abnormal results mean

The presence of a bloody fluid after an injury suggests internal bleeding. Other findings may indicate the following conditions:

  • Infection  
  • Tumor (cancerous or noncancerous)  
  • Appendicitis  
  • Cirrhosis of the liver  
  • Pancreatic disease  
  • kidney disease  
  • Heart disease  
  • Damaged bowel

What the risks are

There is a slight chance of the needle puncturing the bowel, bladder, or a blood vessel in the abdomen. If a large quantity of fluid is removed, there is a slight risk of lowered blood pressure. There is also a slight chance of infection.

Johns Hopkins patient information

Last revised: December 6, 2012
by Dave R. Roger, M.D.

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