Health Information

Abdominal tap

Abdominal tap


An abdominal tap is used to remove fluid from the area between the belly wall and the spine. This space is called the abdominal cavity.

Alternative Names

Peritoneal tap; Paracentesis

How the Test is Performed

This test may be done in a doctor's office, treatment room, or hospital.

The puncture site will be cleaned and shaved, if necessary. You then receive a local numbing medicine. The tap needle is inserted 1 to 2 inches into the abdomen. Sometimes, a small cut is made to help insert the needle. The fluid is pulled out into a syringe.

The needle is removed. A dressing is placed on the puncture site. If a cut was made, one or two stitches may be used to close it.

Sometimes, ultrasound is used to guide the needle. An ultrasound uses sound waves to make the image and not x-rays. It does not hurt.

There are two kinds of abdominal taps:

  • Diagnostic tap -- a small amount of fluid is taken and sent to the laboratory for testing
  • Large volume tap -- several liters may be removed to relieve abdominal pain and fluid buildup

How to Prepare for the Test

Let your health care provider know if you:

  • Have any allergies to medications or numbing medicine
  • Are taking any medications (including herbal remedies)
  • Have any bleeding problems
  • Might be pregnant

How the Test will Feel

You may feel a slight sting from the numbing medicine, or pressure as the needle is inserted.

If a large amount of fluid is taken out, you may feel dizzy or light-headed. Tell the health care provider if you feel dizzy or light-headed.

Why the Test is Performed

Normally, the abdominal cavity contains only a small amount of fluid. In certain conditions, large amounts of fluid can build up in this space.

An abdominal tap can help diagnose the cause of fluid buildup or the presence of an infection. It may also be done to remove a large amount of fluid to reduce belly pain.

Normal Results

Normally, there should be little or no fluid in the abdominal space.

What Abnormal Results Mean

An exam of abdominal fluid may show:


There is a slight chance that the needle could puncture 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 and kidney failure. There is also a slight chance of infection.


Garcia-Tiso G. Cirrhosis and its sequelae. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 156.

Runyon BA. Ascites and spontaneous bacterial peritonitis. In: Feldman M, Friedman LS, Sleisenger MH, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2010:chap 91.

Review Date: 8/19/2014
Reviewed By: Jenifer K. Lehrer, MD, Department of Gastroenterology, Frankford-Torresdale Hospital, Aria Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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