paracentesis

Paracentesis involves inserting a needle or catheter through the abdominal wall into the peritoneal cavity, typically at the left lower quadrant (Point of Lemoine) or midline infraumbilical site, avoiding the inferior epigastric vessels and rectus sheath. Ultrasound guidance improves safety and reduces complications.

Diagnostic paracentesis is indicated in any patient with new-onset ascites, or hospitalized cirrhotic patients with ascites to rule out SBP. Fluid analysis includes cell count with differential, albumin (to calculate serum-ascites albumin gradient, SAAG), total protein, culture, and sometimes cytology, amylase, or triglycerides depending on suspected etiology. SAAG ≥1.1 g/dL suggests portal hypertension (e.g., cirrhosis, heart failure), while SAAG <1.1 g/dL suggests other causes (e.g., malignancy, tuberculosis, nephrotic syndrome). An ascitic fluid absolute neutrophil count ≥250 cells/mm³ is diagnostic of SBP, most commonly caused by E. coli, Klebsiella, and Streptococcus species, and is treated with third-generation cephalosporins (e.g., cefotaxime).

Therapeutic (large-volume) paracentesis is performed to relieve symptoms from tense ascites, such as abdominal discomfort, early satiety, or respiratory compromise. When more than 5 liters are removed, albumin infusion (6-8 g per liter removed) is recommended to prevent post-paracentesis circulatory dysfunction, which can lead to renal failure and hyponatremia due to a rapid drop in intravascular oncotic pressure and effective arterial blood volume.

Complications include bleeding (rare, even with coagulopathy—INR/platelet correction generally not required prophylactically), bowel perforation, infection, and persistent ascitic fluid leak. Contraindications are relative and include severe coagulopathy, bowel obstruction, or infection at the puncture site.