Paracentesis in diagnosis of mesothelioma and relief of symptoms

Paracentesis is a procedure involving inserting a needle through the abdominal wall to remove fluid in the abdominal cavity, called peritoneal or ascetic fluid. The peritoneum is the lining of the abdominal cavity holding the organs in the abdomen and protecting them from infection. The surface of the peritoneum produces a small amount of peritoneal fluid, allowing the organs to slide against the peritoneum and each other without damage.

Paracentesis is commonly done to determine the cause of fluid buildup in the abdominal cavity, a condition known as ascites. Ascites may be caused by infection, inflammation, abdominal injury, or other conditions, such as cirrhosis or cancer. The fluid is sent to a lab for analysis to determine the cause of the fluid buildup. Paracentesis also may be done to drain excess fluid as a comfort measure in people with cancer or chronic cirrhosis, where the fluid is causing pain, difficulty breathing or affecting kidney or intestinal function. Other reasons why paracentesis is done include diagnosing infection in the peritoneal fluid, detecting cancers such as liver cancer and evaluating an abdominal injury.

The Procedure

Paracentesis is usually done in a doctor’s office or an out-patient clinic with only a physician and a nurse to assist. Paracentesis should be performed in a sterile manner; therefore doctors are required to wear sterile gloves and a face shield. In preparation for the procedure, patients lie down with their head slightly elevated and with their abdomen exposed. The abdomen is cleaned with an antiseptic solution and a drape is placed over surrounding areas. The physician will numb a small area of skin by injecting lidocaine and the site for the needle insertion is chosen and marked with a skin-marking pen. The normal site is about 2 cm directly below the belly button since this region has fewer blood vessels. But the insertion site can be slightly to the left of right of this point for different reasons. In obese patients, however, choosing a site to the left of this point is usually preferred, because the abdominal wall there is thinner and the depth of ascitic fluid is deeper in this region than directly below the belly button.

A fairly large-bore needle (about 18 gauge) along with a plastic sheath or catheter is inserted 2 to 5 cm to reach the peritoneal (ascetic) fluid. The needle is then removed, leaving the plastic sheath or catheter behind to allow removal of the fluid. The fluid can be drained by gravity or by connection to a vacuum bottle. If a sample is needed for diagnosing a medical condition, a large syringe is attached to the catheter to withdraw 30 to 60 ml of fluid. If large-volume paracentesis is required, high-pressure connection tubing is attached to the catheter and then to a large container. Additional containers may be filled as necessary. Up to 10 liters of fluid may be drained during the procedure. If fluid drainage is more than 5 liters, patients may receive intravenous fluids containing the blood protein albumin to prevent low blood pressure. Although this practice remains controversial (owing to its high cost and lack of evidence of survival benefit), many experts recommend its use in patients who have had more than 5 liters of fluid removed. Once the desired quantity of fluid has been removed, the catheter is quickly removed and a sterile dressing is applied to the insertion site.

The procedure generally is not painful and patients require no anesthesia. As long as the patient is not too dizzy and maintains their blood pressure after the procedure, they can go home shortly afterwards.

Results of Lab Tests

Serum–ascites albumin gradient values of 1.1 g per deciliter or greater indicates portal hypertension as the cause of the ascites with an accuracy of 97%. Values of less than 1.1 g per deciliter are indicative of other causes of ascites. Patients who receive a diagnosis of spontaneous bacterial peritonitis (SBP) are usually treated with both antibiotics, such as a third-generation cephalosporin, and intravenous albumin.

Risks

In an experienced physician’s hands, paracentesis is very safe, although there is a very small risk of introducing an infection, causing excessive bleeding or puncturing a loop of the bowel. Many patients undergoing paracentesis have some bleeding or inability of their blood to clot during the procedure. However, the occurrence of significant bleeding during paracentesis is extremely low (less than 0.2%), and therefore there is usually no need for blood transfusions. The risk of bleeding complications may be somewhat higher in patients with high creatinine levels in their blood so these patients should be observed for a longer time after the paracentesis. Patients with bleeding or clotting problems or that are taking blood-thinning medications like aspirin, NSAIDs or Coumadin should not have paracentesis done. The procedure should be done with an empty bladder for best results.

The procedure should be performed with caution in pregnant patients or in patients with enlarged organs, bowel obstruction or an enlarged urinary bladder. Using ultrasound to guide the needle insertion in these situations may reduce the risk of injury. A tube should be inserted through the gastric system before paracentesis in patients with bowel obstructions, and patients with problems urinating should first have their bladder emptied with a catheter. The paracentesis needle should not pass through infected sites, enlarged blood vessels, surgical scars, or abdominal-wall blood clots.

Circulatory dysfunction may occur after large-volume paracentesis and is associated with low blood pressure, low blood sodium, and increased blood catecholamine and renin levels. Severe cases may lead to liver or kidney dysfunction and even death. Other complications of paracentesis are rare and include persistent leakage of ascetic fluid and abdominal-wall blood clots. More serious complications include injury to abdominal organs, and puncturing an artery.

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