Paracentesis is a medical procedure used to remove abnormal fluid accumulation, known as ascites, from the peritoneal cavity. This minimally invasive process involves inserting a needle or catheter through the abdominal wall into the fluid-filled space to aspirate the liquid. It is a common and generally well-tolerated procedure performed by healthcare providers to address the discomfort and medical risks associated with excessive fluid buildup. The procedure serves a dual purpose: evaluating the cause of the fluid and providing immediate symptom relief for patients.
Why Paracentesis is Performed
The removal of ascitic fluid is undertaken for two distinct medical purposes: diagnosis and therapy. Diagnostic paracentesis involves collecting a small volume of fluid, typically 25 to 50 milliliters, for laboratory analysis. This analysis helps determine the underlying cause of the ascites, such as liver disease, heart failure, or malignancy, and is particularly important for checking for infection like spontaneous bacterial peritonitis (SBP).
Therapeutic paracentesis is performed to drain a much larger volume of fluid to relieve physical symptoms. Tense ascites can cause significant abdominal discomfort, difficulty breathing due to pressure on the diaphragm, and early satiety. Removing several liters of fluid, sometimes up to 5 to 8 liters in a procedure called large-volume paracentesis, can dramatically improve a patient’s comfort and respiratory function.
Patient Preparation and Site Selection
Patient preparation begins with obtaining informed consent, during which the medical team explains the procedure, its potential benefits, and the risks involved. The patient is asked to empty their bladder immediately before the procedure to minimize the risk of accidental puncture, especially when using a lower abdominal insertion site. Proper positioning is essential, with the patient typically lying supine or semi-recumbent with the head of the bed elevated 45 to 60 degrees. This allows the ascitic fluid to pool in the lower part of the abdomen.
Bedside ultrasound is a modern standard of care used to guide the procedure, which significantly increases safety and success rates. Ultrasound confirms the presence of an adequate fluid pocket and allows the provider to accurately mark a safe insertion point while avoiding underlying structures. This imaging helps to steer clear of structures like the bowel, blood vessels, and the inferior epigastric artery. The preferred insertion site is often in the lower quadrants of the abdomen, lateral to the rectus sheath, or sometimes 2 centimeters below the umbilicus in the midline. Once the site is selected, the area is meticulously cleansed with an antiseptic solution and covered with a sterile drape to establish a sterile field.
Step-by-Step Procedure
The physician first administers a local anesthetic, typically 1% lidocaine, by creating a small raised area, or wheal, on the skin at the marked insertion site. A longer needle is then used to inject the anesthetic progressively deeper along the anticipated path of the catheter, anesthetizing the subcutaneous tissue and the sensitive parietal peritoneum. During this step, the provider intermittently pulls back on the syringe plunger to ensure no blood vessel has been entered before injecting the anesthetic.
In some cases, a small skin incision is made with a scalpel blade to facilitate the smooth passage of the drainage catheter. The paracentesis needle and catheter assembly are then inserted using the Z-track method. This technique involves displacing the skin and underlying subcutaneous tissue laterally before the needle is inserted, creating a non-linear tract through the layers of the abdominal wall. This staggered path helps to seal the entry site once the catheter is removed, significantly reducing the risk of post-procedure fluid leakage.
The needle is advanced slowly while continuous or intermittent negative pressure is applied to the syringe. A distinct loss of resistance is often felt, and ascitic fluid flows into the syringe, confirming entry into the peritoneal cavity. Once fluid return is established, the plastic catheter is threaded over the needle and advanced into the fluid pocket, and the inner needle is withdrawn. For therapeutic drainage, the catheter is connected to a closed drainage system or vacuum bottles to collect the fluid.
If a large volume exceeding five liters is removed, an intravenous albumin infusion may be given concurrently to help prevent complications like paracentesis-induced circulatory dysfunction. Once the required volume of fluid has been drained, the catheter is swiftly removed, and firm pressure is applied to the insertion site.
Post-Procedure Care and Monitoring
Immediate post-procedure care focuses on ensuring patient stability and preventing complications. A sterile adhesive bandage is applied to the insertion site, and if any significant leakage of fluid is noted, a pressure dressing may be required. The patient’s vital signs, including blood pressure and heart rate, are closely monitored for several hours, especially following a large-volume removal, to watch for signs of hypotension or fluid shifts.
Patients are typically advised to limit physical activity for the remainder of the day to allow the puncture site to seal fully. It is normal to experience slight soreness at the site and notice a minimal amount of clear fluid or slight spotting on the dressing. Patients are instructed to watch for signs that may indicate a problem, such as a fever above 100.4°F, excessive redness or swelling, or persistent, bright-red bleeding from the site. Continued or excessive fluid leakage beyond 48 hours is also a symptom that requires further medical attention.