Diagnosis of Spontaneous Bacterial Peritonitis (SBP)

Spontaneous bacterial peritonitis (SBP) is a frequent complication in cirrhotic patients with ascites. Diagnosis of SBP is established by a polymorphonuclear cell count in ascitic fluid > or =250 cells/mm(3).

Indications for diagnostic paracentesis.

• Cirrhotic patients with ascites at admission
• Cirrhotic patients with ascites and signs or symptoms of infection: fever, leukocytosis, abdominal pain
• Cirrhotic patients with ascites who present with a clinical condition that is deteriorating during hospitalization: renal function impairment, hepatic encephalopathy, gastrointestinal bleeding
• Patients with new-onset ascites

Analysis of Peritoneal Fluid

Test and Ascitic-Fluid Container	Comments
Albumin	Differential diagnosis of ascites according to the serum–ascites albumin gradient
Cell	Cell count and differential count
Culture	Aerobic- and anaerobic-culture

 

Additional Analyses of Ascitic Fluid

Test and Ascitic-Fluid Container	Comments
Tube without additives
Total protein	Values >1 g/dl suggest secondary peritonitis instead of SBP
Lactate dehydrogenase	Values greater than the upper limit of normal for serum suggest secondary peritonitis instead of SBP
Glucose	Values <50 mg/dl suggest secondary peritonitis instead of SBP
Carcinoembryonic antigen	Values >5 ng/ml suggest hollow viscus perforation
Alkaline phosphatase	Values >240 U/liter suggest hollow viscus perforation
Amylase	Values markedly elevated (often >2000 U/liter or five times serum levels) in patients with pancreatic ascites or hollow viscus perforation
Triglyceride	Values >200 mg/dl suggest chylous ascites
Syringe or evacuated container
Cytology	Sensitivity increased if three samples submitted and promptly evaluated
Mycobacterial culture	Sensitivity only 50%

 

Differential Diagnosis of Ascites According to the Serum–Ascites Albumin Gradient

Gradient >1.1 g/dl (portal hypertension)	Gradient <1.1 g/dl
Cirrhosis Alcoholic hepatitis Cardiac ascites Portal-vein thrombosis Budd-Chiari syndrome Liver metastases	Peritoneal carcinomatosis Tuberculous peritonitis Pancreatic ascites Biliary ascites Nephrotic syndrome Serositis

The diagnosis of SBP is suggested by a polymorphonuclear (PMN) cell count in excess of 250 cells per cubic millimeter in the absence of evidence of an alternative source of infection (secondary peritonitis), such as viscus perforation or intraabdominal abscess.

Determination of total protein, lactate dehydrogenase, and glucose levels in ascitic fluid may aid in the differentiation between SBP and secondary peritonitis. Culture is used to confirm the diagnosis of SBP.

 

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