What laboratory abnormalities are expected in a patient requiring paracentesis?

Laboratory Abnormalities in Patients Requiring Paracentesis

Patients requiring paracentesis typically show abnormal liver function tests, coagulation parameters, and electrolyte imbalances, with the most common being prolonged prothrombin time, thrombocytopenia, hyponatremia, and elevated serum creatinine. 1

Key Laboratory Abnormalities

Liver Function Tests

• Elevated liver enzymes (AST, ALT)
• Elevated bilirubin (direct and indirect)
• Decreased albumin levels
• Elevated alkaline phosphatase

Coagulation Parameters

• Prolonged prothrombin time (PT) and international normalized ratio (INR)
  • Most patients with cirrhosis and ascites have abnormal PT/INR 1
  • Despite these abnormalities, paracentesis is still safe in these patients 1
• Thrombocytopenia (low platelet count)
  • Often <50,000/mm³ in advanced cirrhosis 1

Electrolyte and Renal Function Abnormalities

• Hyponatremia (serum sodium <135 mEq/L)
• Elevated serum creatinine (indicating renal dysfunction)
• Hypokalemia or hyperkalemia (depending on diuretic use)
• Elevated blood urea nitrogen (BUN)

Specific Patterns by Etiology

Cirrhotic Ascites (Most Common)

• Low serum albumin (<3.5 g/dL)
• Elevated serum-ascites albumin gradient (SAAG) >1.1 g/dL 1
• Ascitic fluid protein typically <2.5 g/dL
• Ascitic fluid neutrophil count <250 cells/mm³ (unless infected) 1

Spontaneous Bacterial Peritonitis

• Ascitic fluid neutrophil count >250 cells/mm³ 1
• Positive ascitic fluid bacterial culture
• Elevated serum white blood cell count
• Elevated C-reactive protein

Malignant Ascites

• Positive ascitic fluid cytology
• Elevated ascitic fluid protein (often >2.5 g/dL)
• Elevated tumor markers (e.g., CA-125, CEA)

Heart Failure-Related Ascites

• Elevated pro-brain natriuretic peptide (>6000 pg/mL) 1
• Elevated ascitic fluid protein (often >2.5 g/dL)

Secondary Bacterial Peritonitis

• Ascitic glucose <50 mg/dL
• Ascitic LDH higher than serum LDH
• Elevated ascitic CEA (>5 ng/mL) or alkaline phosphatase (>240 U/L) 1

Important Clinical Considerations

1. Coagulation abnormalities are common but rarely contraindicate paracentesis:

   • Studies show paracentesis is safe despite INR values as high as 8.7 and platelet counts as low as 19,000/mm³ 1
   • Prophylactic transfusions are generally not necessary unless there is clinically evident hyperfibrinolysis or disseminated intravascular coagulation 1

2. Renal dysfunction increases bleeding risk:

   • Patients with renal failure have higher risk of bleeding complications during paracentesis 1
   • Monitor renal function parameters carefully

3. Monitoring for post-paracentesis complications:

   • Paracentesis-induced circulatory dysfunction (PICD) can occur after large-volume paracentesis 2
   • Monitor for worsening hyponatremia and renal impairment post-procedure

Pitfalls to Avoid

1. Don't withhold paracentesis due to abnormal coagulation parameters alone

   • Paracentesis is generally safe despite coagulopathy 1

2. Don't miss spontaneous bacterial peritonitis

   • Always check ascitic fluid cell count and culture in hospitalized patients 1
   • SBP can be present in 15% of hospitalized cirrhotic patients with ascites 1

3. Don't assume a single cause of ascites

   • Approximately 5% of patients have multiple causes of ascites formation 1

4. Don't rely on clinical symptoms alone to diagnose SBP

   • SBP can be asymptomatic in up to 7% of cases 3
   • Routine diagnostic paracentesis is recommended for all cirrhotic patients admitted with ascites 3

By understanding these laboratory abnormalities, clinicians can better diagnose the underlying cause of ascites and monitor for potential complications during and after paracentesis.