What is the recommended workup for a patient with chronic ascites?

Chronic Ascites Workup

All patients with chronic ascites require diagnostic paracentesis at every hospital admission and when new symptoms develop, with ascitic fluid analysis including cell count with differential, total protein, SAAG calculation, and bedside inoculation of blood culture bottles. 1

Initial Diagnostic Paracentesis

Perform diagnostic paracentesis in all patients with:

• New-onset ascites 1
• Any hospital admission (even without symptoms) 1
• Clinical deterioration: fever, abdominal pain, encephalopathy, GI bleeding, shock, worsening renal or liver function 1

Essential Ascitic Fluid Analysis

Mandatory initial tests:

• Cell count with differential - PMN count >250/mm³ diagnoses spontaneous bacterial peritonitis (SBP), performed by manual microscopy or automated flow cytometry 1
• Total protein concentration 1
• Serum-ascites albumin gradient (SAAG) - calculated from simultaneous serum and ascitic fluid albumin levels 1
• Gram stain and culture - bedside inoculation of at least 10 mL into aerobic and anaerobic blood culture bottles before any antibiotics, increases sensitivity to >90% 1, 2

Additional tests based on clinical suspicion:

• Cytology (if malignancy suspected) 1
• Amylase (if pancreatic ascites suspected) 1
• Brain natriuretic peptide/BNP (if cardiac ascites suspected) 1
• Adenosine deaminase (if tuberculous peritonitis suspected) 1

Interpretation Framework

SAAG interpretation:

• SAAG ≥1.1 g/dL indicates portal hypertension (cirrhosis, cardiac failure, Budd-Chiari) 1
• SAAG <1.1 g/dL suggests non-portal hypertensive causes (malignancy, tuberculosis, pancreatic ascites) 1

Critical action threshold:

• PMN count >250/mm³ requires immediate empirical antibiotics before culture results, typically third-generation cephalosporins (cefotaxime 2g IV q12h) in community-acquired cases 1
• In nosocomial or critically ill patients, broader coverage with carbapenems should be considered due to multidrug-resistant organisms 1

Concurrent Blood Work

Obtain simultaneous serum samples for:

• Albumin (required for SAAG calculation) 1
• Blood cultures (increases organism isolation rates) 1
• Electrolytes and renal function 2

Special Circumstances

If pleural effusion present without ascites or with negative ascitic fluid analysis:

• Perform diagnostic thoracentesis when bacterial infection suspected (hepatic hydrothorax) 1, 2

Repeat paracentesis at 48 hours:

• Consider in patients with inadequate response to antibiotics or when secondary bacterial peritonitis suspected 1

Common Pitfalls to Avoid

• Never delay paracentesis for coagulopathy correction - bleeding risk is minimal even with INR elevation 1
• Never start antibiotics before obtaining fluid for culture - dramatically reduces diagnostic yield 1
• Never send ascitic fluid to laboratory in standard containers - bedside inoculation into blood culture bottles is essential for adequate sensitivity 1
• Never assume absence of infection based on symptoms alone - SBP can be asymptomatic in up to 30% of cases 1