What are the peritoneal fluid findings in Spontaneous Bacterial Peritonitis (SBP)?

From the Guidelines

Spontaneous Bacterial Peritonitis (SBP) is diagnosed when the ascitic neutrophil count is >250 cells/mm3.

Peritoneal Fluid Findings in SBP

The diagnosis of SBP is based on the analysis of peritoneal fluid findings, including:

• Ascitic neutrophil count: >250 cells/mm3 is considered diagnostic of SBP 1
• Ascitic fluid culture: although culture is frequently negative, it is essential to guide antibiotic therapy 1
• Total white cell count (WCC): >1000 cells/μL can also be used to diagnose SBP, with a positive likelihood ratio of 9.1 (95% CI 5.5 to 15.1) 1
• Polymorphonuclear leukocyte (PMN) count: ≥500 cells/μL has greater specificity for the diagnosis of SBP, with a positive likelihood ratio of 10.6 (95% CI 6.1 to 18.3) 1 Some key points to consider:
• Adjusted PMN count: if there are red blood cells (RBCs) in the ascites, the PMN count is adjusted by subtracting 1 PMN per 250 RBCs/mm3 1
• Culture-negative neutrocytic ascites: approximately 40% of patients with an ascitic PMN count ≥250/mm3 are culture-negative, but still require empirical antibiotic therapy 1
• Monomicrobial non-neutrocytic bacterascites: a single strain of bacteria is cultured in the ascitic fluid, but the ascitic PMN count <250/mm3, indicating colonization of bacteria in the ascites 1

From the Research

Peritoneal Fluid Findings in Spontaneous Bacterial Peritonitis (SBP)

The peritoneal fluid findings in SBP include:

• Ascitic fluid with 250 or more neutrophils/mm³, which is an acceptable criterion for diagnosis, even when bacterial fluid cultures are negative 2
• Higher lactate dehydrogenase levels in patients with SBP compared to those without SBP 2
• Presence of bacterial DNA in peritoneal fluid, which is an indicator of SBP 3
• Growth of Gram-positive bacteria in peritoneal fluid cultures, although Gram-negative bacteria can also be present 4
• Low ascitic fluid total protein concentration, which may increase the risk of bacterial infection 5

Diagnostic Criteria

The diagnostic criteria for SBP include:

• Ascitic fluid neutrophil count greater than 250 cells/cu mm 2, 5
• Positive bacterial culture of ascitic fluid 2, 3
• Clinical suspicion and analysis of ascitic fluid, especially white cell count and culture in blood culture bottles 6

Laboratory Characteristics

The laboratory characteristics of ascitic fluid in SBP include:

• Elevated lactate dehydrogenase levels 2
• Elevated adenosine deaminase levels 2
• Low glucose concentrations 2
• Presence of bacterial DNA 3
• Growth of pathogens commonly associated with SBP, such as Gram-positive and Gram-negative bacteria 2, 4