Written By: Karen Selby, RN,
Last modified: December 23, 2020

The peritoneal linings create a space that separates the organs of the belly from the abdominal wall, and there is a small amount of natural lubricant that collects between the two layers of this lining. When more than an ounce (30 ml) of fluid develops in the peritoneal cavity, it is called ascites or ascitic fluid. When too much ascitic fluid builds up in the peritoneal space, it can put pressure on the abdominal organs and the diaphragm. This accumulation of ascitic fluid can be caused by infection, injury, liver damage or cancer. Ascites is commonly found in cases of peritoneal mesothelioma.

A paracentesis, also known as an “abdominal tap” or “ascites tap,” is a minor surgical procedure in which a doctor drains excess ascitic fluid from the patient’s abdomen through a hollow needle. If the purpose is only to diagnose the cause of the ascites, a doctor may take as little as 50 mL of fluid for analysis. For a therapeutic paracentesis, a doctor may drain a liter of fluid or more.

Quick Facts About Paracentesis

  • Drains excess fluid from abdominal lining
  • Usually performed as out-patient procedure
  • Temporarily treats abdominal symptoms
  • Less invasive than other surgical treatments

Ascites often develops in people with peritoneal mesothelioma because widespread abdominal tumors can cause a condition known as peritoneal carcinomatosis. Tumors may damage the linings of the peritoneal cavity, thus blocking the lymphatic system that normally regulates the flow of fluid in and out of the abdomen. They may also weaken the endothelial cells in the abdominal wall that normally stop protein and fat from leaking out of blood vessels and accumulating in the peritoneal cavity.

Ascites Drainage Diagram
Diagram of Ascites Drainage

Though paracentesis can be effective for relieving symptoms of peritoneal mesothelioma, analyzing ascitic fluid is not a reliable way to diagnose this rare type of cancer. The cells found in ascitic fluid often appear benign even when cancer is present, which is why a biopsy for tissue sampling, not just the cytological analysis of cells in the drained ascites, is essential to diagnosing mesothelioma.

Palliative Paracentesis Benefits and Alternatives

Because paracentesis is a minor procedure that does not usually require a hospital stay, it can alleviate symptoms and improve quality of life for patients with any stage of cancer. Its main limitation is that it is a palliative treatment, and it does not prevent the patient from developing ascites again in the future.

Many peritoneal mesothelioma patients have a high rate of ascites recurrence, so rather than performing repeated paracentesis procedures, doctors prefer to leave a catheter in place to continuously drain the peritoneal cavity. In addition, if tumor development causes the ascitic fluid to become loculated (meaning it builds up in smaller spaces in the abdomen and does not flow freely in the peritoneal cavity), paracentesis will be less effective.

For peritoneal patients healthy enough to qualify for aggressive cancer treatment, many leading mesothelioma specialists recommend tumor-removing surgery in combination with hyperthermic intraperitoneal chemotherapy (HIPEC), a multimodal approach that has revolutionized the treatment of abdominal cancer in recent years. A 2016 review noted HIPEC successfully controls ascites in more than 90 percent of patients.

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The Paracentesis Procedure

Paracentesis is often performed as an outpatient procedure, taking approximately 20 to 30 minutes. In many cases, an ultrasound is first administered to better visualize the size and scope of the ascitic fluid buildup.

After making sure their bladder is empty, the patient lays on a bed elevated at a 45-degree angle to allow fluid to accumulate in their lower abdomen. The doctor cleans the insertion site with antiseptic and numbs it with a local anesthetic before inserting a large-bore needle to reach the peritoneal cavity.

Once the ascitic fluid begins to flow, the cavity is drained either by gravity, a syringe or connection to a vacuum bottle. Doctors typically drain only one liter of fluid at a time, no faster than 500 mL every 10 minutes, so the body can equilibrate fluids and electrolytes. If several liters of fluid are drained during the procedure, the patient may receive serum albumin to replace lost fluid, prevent a drop in blood pressure and reduce the risk of shock.

After the desired level of drainage is complete, the doctor covers the insertion site with a sterile dressing and a small suture, if necessary. Alternatively, if the procedure is going to be repeated, a catheter with a flow-control valve and protective dressing can be left in place.

The patient is usually discharged within a few hours, provided their blood pressure is normal and they have no feeling of dizziness.

Risks and Complications

A paracentesis is a fairly simple procedure that presents very few risks. Rare complications include:

  • Infection
  • Persistent leak from the insertion site
  • Abdominal wall hematoma (collection of blood outside a blood vessel)
  • Perforation of the small or large intestine, stomach or bladder
  • Hypotension (low blood pressure)

One documented complication that occurred in a patient with peritoneal mesothelioma was the repeated occurrence of a pneumothorax after a paracentesis procedure. A pneumothorax occurs when air builds up in the space around the lungs and doesn’t allow the lung to expand fully. This is a rare complication, but doctors feel it should be considered in patients with pre-existing pulmonary disease.


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