W10 Paracentesis and Diagnostic Peritoneal Lavage
Paracentesis: Before Procedure
Indications
• Paracentesis is the insertion of a needle or catheter into the peritoneal cavity for the purpose of aspirating peritoneal fluid. It is most often indicated for diagnostic or therapeutic evacuation of ascites.
Anatomy
Procedure
• The patient should be supine. Bedside ultrasonography can be a valuable aid for localizing the largest collection of ascites and avoiding injury to the bowel and should be employed routinely. The patient should void or have a urinary bladder drainage tube inserted before the procedure. The area is cleansed, draped, and anesthetized.
• When a small volume of ascitic fluid is needed for diagnostic studies, an 18- or 20-gauge, 2- to 3-inch needle attached to a 20- to 50-mL syringe is inserted into the abdomen lateral to the rectus muscle in the lower quadrant, midway between the umbilicus and the anterior superior iliac spine, avoiding prior surgical incisions. The skin is retracted caudad while inserting the needle. When fluid is aspirated, the needle is stabilized and the fluid sample is obtained by syringe. After removal of the needle, the skin is released, causing the entrance and exit needle sites to form a “Z-track” that reduces the chance of ascitic fluid leakage.
• For large-volume paracentesis, a 14- to 16-gauge cannula-over-needle is employed. Once fluid is aspirated in the syringe, the needle is removed, leaving the plastic catheter in place, which is attached to plastic tubing and to a vacuum canister. Usually 4 to 6 L of ascites can be safely removed, although larger volumes have been removed.
• If it is necessary to place a catheter into the peritoneal cavity, a guidewire should be inserted into the peritoneal cavity through the needle; an 8.5F 40-cm polyurethane pigtail catheter should be guided into the peritoneal cavity over the wire and sutured in place.
• The aspirated fluid should be submitted for cell count, absolute polymorphonuclear neutrophil count, albumin, total protein concentration, Gram stain, and cultures. Optional studies, based on clinical suspicion, may include glucose concentration, amylase concentration, lactate dehydrogenase concentration, bilirubin concentration, and cytology.
After Procedure
Postprocedure Care
Complications
• Common:
• Hypotension:
• Hypotension after paracentesis in cirrhotic patients can be associated with worsening of arteriolar vasodilation.1 In the first few hours after large-volume paracentesis, there is a reduction in plasma levels of renin and aldosterone, an increase in atrial natriuretic peptide concentration, a reduction in cardiac filling pressures, and an increase in cardiac index.
• However, after 12 to 24 hours, these changes reverse, reflecting effective hypovolemia. Infusion of intravenous colloids, specifically albumin, has been shown to attenuate the hemodynamic consequences of paracentesis and the associated neurohumoral alterations.2 However, no large randomized study has shown that routine expansion of plasma volume with a colloid solution confers a survival advantage.
Outcomes and Evidence
• Determining the etiology of ascites is based on the patient’s history, physical examination, liver function tests, ultrasonography, and ascitic fluid analysis. Abdominal paracentesis and ascitic fluid analysis should be an early step in the workup of patients with new-onset ascites. Paracentesis is also important to diagnose infection of ascitic fluid (i.e., peritonitis).
• Development of ascites is a common complication of cirrhosis, being more frequent than either encephalopathy and variceal hemorrhage in these patients. The median survival of cirrhotic patients with ascites is 2 years.5 Other causes of ascites besides cirrhosis include malignancy, heart failure, tuberculosis, renal failure, and pancreatic disease.
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