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Diagnosis of Spontaneous Bacterial Peritonitis (SBP)

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



Differential diagnosis of ascites according to the serum–ascites albumin gradient


Cell count and differential count


Aerobic- and anaerobic-culture

Additional Analyses of Ascitic Fluid

Test and Ascitic-Fluid Container


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


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


Values markedly elevated (often >2000 U/liter or five times serum levels) in patients with pancreatic ascites or hollow viscus perforation


Values >200 mg/dl suggest chylous ascites

Syringe or evacuated container


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


Alcoholic hepatitis

Cardiac ascites

Portal-vein thrombosis

Budd-Chiari syndrome

Liver metastases

Peritoneal carcinomatosis

Tuberculous peritonitis

Pancreatic ascites

Biliary ascites

Nephrotic syndrome


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.


Related Criteria

Diagnostic Criteria for Zollinger-Ellison Syndrome (ZES)

Diagnostic Criteria for Autoimmune Hepatitis (AIH)

Diagnostic Criteria for Wilson's disease

Severity Criteria for Acute Pancreatitis




  1. Fernandez J, Bauer TM, Navasa M, Rodes J. Diagnosis, treatment and prevention of spontaneous bacterial peritonitis. Baillieres Best Pract Res Clin Gastroenterol. 2000 Dec;14(6):975-990. [Medline]

  2. Thomsen TW, Shaffer RW, White B, Setnik GS. Videos in clinical medicine. Paracentesis. N Engl J Med. 2006 Nov 9;355(19):e21. [Medline]

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Created: Apr 17, 2007
Last Modified: 10/17/2010

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