OVERVIEW
Evaluating for spontaneous bacterial peritonitis (SBP) is a very common indication for ordering and performing a diagnostic paracentesis. It is for this reason that it is useful to understand exactly how the diagnosis of SBP is made.
WHAT IS THE DIAGNOSTIC CRITERIA FOR SBP?
The diagnosis of SBP is made typically when there is are the following findings:
- Elevated number of polymorphonuclear cells (PMNs/neutrophils) in the ascites. The cutoff that is typically used is ≥250 cells/mm³.
- Positive ascites fluid bacterial culture: seen on the gram stain and/or the culture
- No other clear cause of peritonitis: such as etiologies like bowel perforation.
HOW IS THE NUMBER OF PMNs IN THE ASCITES FLUID CALCULATED:
This concentration of PMNs in the ascites fluid is calculated by taking the total white blood cell count and multiplying it by the percentage of PMNs in the differential provided by the lab.
Page Updated: 09.01.2019