What tests should be sent immediately after paracentesis in a patient with liver disease and gross ascites?

Tests to Send Immediately After Paracentesis

Send ascitic fluid for cell count with differential (specifically neutrophil count), inoculate two blood culture bottles at bedside, and measure ascitic fluid albumin—these three tests are mandatory for every paracentesis to screen for spontaneous bacterial peritonitis and determine the serum-ascites albumin gradient. 1, 2

Essential Ascitic Fluid Tests (All Patients)

Immediate Bedside Inoculation

• Inoculate 10 mL of ascitic fluid into two aerobic blood culture bottles immediately at bedside to maximize detection of spontaneous bacterial peritonitis (SBP), which is present in approximately 15% of hospitalized cirrhotic patients with ascites 1, 2
• Bedside inoculation significantly increases culture yield compared to delayed laboratory processing 2

Cell Count and Differential

• Send ascitic fluid in an EDTA tube for cell count with differential, specifically requesting absolute neutrophil count 1
• An ascitic neutrophil count ≥250 cells/mm³ is diagnostic of SBP and requires immediate empiric antibiotic therapy even before culture results return 1, 2
• This is the single most critical test for preventing mortality from untreated SBP 2

Ascitic Fluid Albumin

• Measure ascitic fluid albumin to calculate the serum-ascites albumin gradient (SAAG) 1
• A SAAG ≥1.1 g/dL confirms portal hypertension as the cause of ascites with 97% accuracy 1
• This distinguishes cirrhotic ascites from other causes (malignancy, infection, pancreatitis) 1

Conditional Ascitic Fluid Tests

Ascitic Fluid Amylase

• Send ascitic fluid amylase if pancreatic ascites is suspected (history of pancreatitis, upper abdominal pain, or elevated serum amylase) 1
• Ascitic fluid amylase >2-3 times serum amylase suggests pancreatic ascites 1

Ascitic Fluid Cytology

• Send ascitic fluid cytology only when malignancy is clinically suspected (known cancer history, bloody ascites, or unexplained ascites in non-cirrhotic patient) 1
• Do not send routinely in known cirrhotic ascites as yield is extremely low and not cost-effective 1
• Note that bloody ascites in cirrhotics has a 30% association with hepatocellular carcinoma 1

Concurrent Blood Tests

Mandatory Blood Work

• Draw serum albumin simultaneously with paracentesis to calculate SAAG (serum albumin minus ascitic fluid albumin) 1
• Send complete metabolic panel including creatinine, BUN, and electrolytes to assess for hepatorenal syndrome, hyponatremia, and renal dysfunction 1
• Obtain liver function tests (bilirubin, AST, ALT, alkaline phosphatase) and prothrombin time/INR 1
• Complete blood count to assess for thrombocytopenia and anemia 1

Critical Pitfalls to Avoid

• Never delay sending ascitic fluid for cell count and culture—SBP can be rapidly fatal if untreated 1, 2
• Never wait for culture results to start antibiotics if neutrophil count is ≥250 cells/mm³—empiric therapy must begin immediately as mortality increases with each hour of delay 2
• Never send routine coagulation studies before paracentesis or transfuse blood products prophylactically—paracentesis is safe even with INR >2.0 and platelets >40,000, and routine transfusion wastes resources without improving safety 1, 2
• Never forget to send serum albumin concurrently—you cannot calculate SAAG without it, and this is essential for determining the etiology of ascites 1