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Paracentesis is a procedure that removes ascitic fluid from the abdominal cavity with a needle or a catheter. A diagnostic paracentesis may determine the cause of ascites and rule out spontaneous bacterial peritonitis. A therapeutic paracentesis will remove excess fluid.

The mechanism for the development of ascites (excess fluid accumulation in the peritoneal space) is not well understood. Cirrhosis is the leading cause of ascites due to portal hypertension. Capillary pressure increases with obstruction of venous blood flow through the damaged liver. Reduced hepatic metabolism of aldosterone increases renal sodium and water retention. Reduced hepatic synthesis of albumin contributes to fluid moving from the vascular space into the peritoneal space. In addition to cirrhosis, other causes of portal hypertension include right heart failure, portal vein thrombosis, Budd-Chiari syndrome, and liver metastases. Pancreatitis, chylous fluid accumulation, nephritic syndrome, serositis, colitis, peritoneal carcinomatosis, tuberculous peritonitis, and peritonitis may cause ascites through a different mechanism.

Any amount of peritoneal fluid withdrawn during paracentesis is abnormal. A diagnostic test (60 cc of fluid) includes:

  • Cell count and differential (few mL)

  • Gram stain and culture (ideally, 5 mL in an anaerobic and aerobic blood culture bottle)

  • Simultaneous serum albumin to calculate a serum albumin ascites gradient (few mL)

  • Cytology (the more fluid, the greater yield)

Other studies such as amylase, triglycerides, and AFB are performed only if clinically indicated.

Figure 126-1

Practice algorithm: preprocedure preparation.

Table 126-1Basic Considerations

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