Paracentesis
Paracentesis is a medical procedure that involves inserting a needle or catheter through the peritoneum, the membrane lining the abdominal cavity, to either sample or drain excess fluid. This procedure is often performed to diagnose or manage conditions associated with fluid buildup in the abdomen, known as ascites, which can occur in various cancers, including liver, pancreatic, and ovarian cancer. Paracentesis serves both diagnostic and therapeutic purposes, helping to identify cancer cells and relieve discomfort caused by large fluid accumulations.
Before the procedure, patients undergo blood tests and an ultrasound to ensure safety and determine the best approach. The procedure itself is typically conducted in an outpatient setting, requiring local anesthesia and careful monitoring of the patient’s vital signs afterward. Although paracentesis is generally safe, potential risks include injury to surrounding organs and the possibility of infections. Laboratory analysis of the drained fluid provides critical insights into the patient's health, revealing information about potential infections, cancers, or other underlying conditions. Recent advancements in technique and equipment have improved the safety and effectiveness of paracentesis, making it a valuable tool in the management of ascitic conditions.
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Subject Terms
Paracentesis
ALSO KNOWN AS: Abdominal tap, abdominal paracentesis, peritoneal tap
DEFINITION: Paracentesis is the insertion of a needle or catheter through the peritoneum, the membrane that lines the abdominal cavity, to sample or drain excess fluid.
Cancers diagnosed or treated: Most metastatic cancers, especially liver cancer, colon cancer, pancreatic cancer, mesothelioma, and ovarian cancer
Why performed: Paracentesis is primarily a diagnostic but sometimes a therapeutic procedure. It is performed to identify new cancer cells that have metastasized to the abdomen or to analyze the extent of existing cancer-causing fluid buildup (ascites) in the peritoneal space. In the latter case, physicians may perform paracentesis to remove a large amount of fluid and relieve the patient of pain in the lungs, kidneys, and bowels.
Patient preparation: The physician will discuss risks, benefits, and alternatives with the patient and ask them to sign an informed consent form. A few days before the procedure, the patient undergoes blood tests to confirm no clotting or bleeding problems in the abdomen. On the day of the procedure, a radiologist will perform an ultrasound scan of the peritoneal space to assess the size and area of the ascites. Immediately before the test, the patient must urinate to leave an empty bladder.
Steps of the procedure: Non-emergency paracentesis is scheduled in an outpatient setting. The abdominal area is cleaned with an antiseptic soap, and a local anesthetic such as lidocaine is injected into the patient’s abdomen. Based on the ultrasound and percussion of the abdomen, the physician chooses the insertion site for paracentesis. Typically, the patient sits in a semi-recumbent position, so a site just below the navel is optimal for insertion and fluid aspiration. A nurse will shave this area of the abdomen if needed. When enough fluid has been removed (an average of 25 milliliters in diagnostic paracentesis and up to 10 liters in therapeutic paracentesis), the physician withdraws the needle from the abdomen and applies direct pressure to the puncture site with a sterile dressing. Large accumulations of fluid require the insertion of a vacuum-pressurized catheter, through which the fluid can drain into a container. Results are sent to the laboratory for analysis right away. The entire procedure takes ten to thirty minutes.
After the procedure: The patient rests for one to four hours while vital signs, site, and fluid drainage are monitored. If large amounts of fluid are drained, then nurses will actively monitor the patient’s blood pressure for hypotension and shock. An intravenous (IV) line may be inserted to avoid fluid shifts in the body and prevent kidney failure. Slight fluid drainage from the puncture site may continue for one to two days. Normally, the patient does not require an overnight stay.
In the twenty-first century, advances have been made in paracentesis. Introducing a low-flow pump system that moves fluid from the peritoneal cavity into the bladder has reduced the need for large-volume paracentesis. New methods of needle insertion have minimized ascitic fluid leakage. Fluid leaks were also minimized through new suturing techniques and cyanoacrylate skin adhesive. Finally, doctors often use a left-lateral approach to paracentesis, which avoids the bowel.
Risks: Paracentesis is a relatively safe procedure. Although the incidence of any particular complication is rare, a range of intraprocedure complications may occur. The paracentesis needle may perforate the bladder, bowels, or blood vessels in the abdomen, causing internal bleeding or hemorrhage. Infection of the peritoneal fluid or the spread of cancer inside the abdomen are also risks associated with the paracentesis needle. The risk of external infection around the puncture site is increased if there is persistent leakage from the puncture site.
Results: Patients undergo paracentesis only if they have ascites, an abnormal condition, in the abdomen. Several laboratory tests are performed on the peritoneal fluid to assess the abnormality. A high white blood cell count may indicate inflammation, bacterial peritonitis, infection, or cancer in the abdomen. High albumin protein content in the fluid, as compared to the content in the patient’s blood serum, may indicate tuberculosis, kidney disorder, pancreatitis, or cancer. Lower protein content may indicate liver cirrhosis or portal hypertension. A high level of the enzyme lactate dehydrogenase in the fluid may indicate infection or cancer. A high level of the enzyme amylase may indicate pancreatitis. A low level of glucose may indicate infection. Cells from the fluid will undergo culture and pathology in the laboratory to confirm the type of infection or cancer. A biopsy may also be performed.
Bibliography
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