Peritoneal fluid analysis is also known as paracentesis or an abdominal tap. An analysis is recommended when an abnormal amount of fluid collects in the peritoneal space (part of the abdomen that contains the gastrointestinal organs).
A doctor withdraws the fluid by numbing the skin and inserting a long, thin needle into the peritoneal space. The fluid drains into collection containers. These containers are sent to the laboratory to undergo a series of tests. The results of all of these tests taken together help your doctor reach a diagnosis and decide on the best treatment plan for you.
The most common reason for performing peritoneal fluid analysis is to determine why an unusual amount of fluid is building up in the abdomen.
Peritoneal fluid analysis is also the test doctors use to diagnose peritonitis, a potentially fatal bacterial or fungal infection of the lining of the inner abdominal wall. Trauma teams may use paracentesis to quickly check for internal bleeding in patients who have experienced abdominal trauma.
A doctor in either an inpatient or an outpatient setting can perform peritoneal fluid analysis. Before the procedure, a technician will direct you to remove your clothes and change into a hospital gown.
If only a small amount of fluid is going to be withdrawn, you can sit up during the test. If the doctor anticipates withdrawing a large amount of fluid, the technician will position you lying on your back with your head slightly elevated.
The doctor then cleans the area of the abdomen where he or she will insert the needle. The antiseptic may feel cold against your skin, but it will not hurt. Once the skin is cleansed, the doctor will drape your abdomen with a sterile covering.
The doctor will then inject a small amount of local anesthetic into the skin. You will feel a needle prick, and the injection itself will sting. However, the discomfort does not last long the skin will go numb.
Once the skin is numbed, the doctor injects a long, hollow needle into the peritoneal area and pulls back on the plunger, drawing the fluid out of your abdomen. You may feel a dull pain or pressure during this procedure. If the doctor withdraws a large amount of fluid, you may feel dizzy and light-headed. If this happens, tell the doctor immediately.
It is important to remain as still as possible until the test is completed. Paracentesis takes around 30 minutes and may involve the removal of more than a gallon of fluid from the peritoneal area.
Peritoneal fluid analysis is considered a safe procedure. The most common negative outcome is low blood pressure, which occurs when a large amount of fluid is removed from the body. It can be treated by administering intravenous (IV) fluids.
Other potential risks include damage to the surrounding organs and infection at the puncture site.
Once the procedure is completed, the doctor will apply a bandage or small surgical dressing to the puncture site. You may notice a small amount of clear drainage from the site for the next two to three days.
The doctor then checks your vital signs and monitors your blood pressure for a short time to make sure it doesn’t drop unexpectedly.
Unless your doctor tells you otherwise, you should be able to return to all of your usual activities once the test is finished.
Call your doctor or return to the hospital immediately if you:
• develop a temperature of over 100 degrees F
• experience severe abdominal pain, tenderness, or redness
• notice heavy bleeding or discharge at the puncture site.
The laboratory technicians perform many tests on the peritoneal fluid. They check the general appearance to see whether it is clear, red-tinged, or milky-white. They test for albumin and protein levels, and do a count of red and white blood cells in the sample.
The sample is also tested for bacteria or fungi, which could be causing an infection. Finally, the technicians look at the size and shape of the cells—a practice known as cytology—to see if any of the cells show changes that could indicate cancer.
There are a few indications doctors are quick to recognize (Shah, 2012):
- Bile-stained fluid indicates gallbladder or liver disease.
- Pink or red fluid implies internal bleeding.
- Large difference between amount of albumin in peritoneal fluid and amount of albumin in blood suggests failure of the heart, liver, or kidneys.
- Increased white cell count may indicate an inflammation or infection (peritonitis).
- Increased protein in the sample could indicate either liver disease or cancer.
Although a great many tests are run on peritoneal fluid, the preliminary results take less than a day to process. Once your doctor receives them, he or she will make treatment suggestions or possibly recommend a round of more specialized tests to address the organ that appears to be causing your problem.