(See also How To Do Paracentesis.)
Abdominal paracentesis is used to obtain ascitic fluid for testing. It also can be used to remove tense ascites causing respiratory difficulties or pain or as a treatment for chronic ascites.
Absolute contraindications to paracentesis include
Severe, uncorrectable disorders of blood coagulation
An infected abdominal wall
Intestinal obstruction (unless an area of peritoneal fluid that can be safely entered has been identified using imaging studies)
Poor patient cooperation, surgical scarring over the puncture area, large intra-abdominal masses, and severe portal hypertension with abdominal collateral circulation are relative contraindications.
Complete blood count, platelet count, and coagulation studies are done before the procedure. After emptying the bladder, the patient sits in bed with the head elevated 45 to 90°. In patients with obvious and marked ascites, a point is located at the midline between the umbilicus and the pubic bone and is cleaned with an antiseptic solution and alcohol. Two other possible sites for paracentesis are located about 3 to 5 cm superior and medial to the anterior superior iliac spine on either side. In patients with moderate ascites, precise location of ascitic fluid by abdominal ultrasound is indicated. Positioning the patient in a lateral decubitus position with the planned insertion site down also promotes the floating and migration of air-filled bowel loops up and away from the point of entry.
Under sterile technique, the area is anesthetized to the peritoneum with lidocaine 1%. For diagnostic paracentesis, an 18- to 22-gauge (1.5-inch or 3.5-inch) needle attached to a 30- to 50-mL syringe is inserted through the peritoneum (generally a popping sensation is noted). Fluid is gently aspirated and sent for cell count, protein or amylase content, cytology, or culture as needed. For therapeutic (large-volume) paracentesis, an 18- to 14-gauge (1.5-inch or 3.5-inch) cannula attached to a vacuum aspiration system is used to collect up to 8 L of ascitic fluid. Concurrent infusion of IV albumin is recommended during large-volume paracentesis to help avoid significant intravascular volume shift and postprocedural hypotension.
Hemorrhage is the most common complication of paracentesis. Occasionally, with tense ascites, prolonged leakage of ascitic fluid occurs through the needle site.