From the Guidelines
Spontaneous bacterial peritonitis (SBP) is diagnosed when the peritoneal fluid neutrophil count exceeds 250 cells/mm³ in patients with ascites, typically those with cirrhosis. This threshold is the established diagnostic criterion regardless of whether bacteria are cultured from the fluid, as indicated by the guidelines on the management of ascites in cirrhosis 1. The elevated neutrophil count indicates an inflammatory response to bacterial infection within the peritoneal cavity.
Diagnostic Criteria
In clinical practice, a paracentesis (removal of ascitic fluid) is performed to obtain the fluid for cell count and culture. The total white blood cell count in peritoneal fluid may be higher, but the neutrophil component specifically must exceed 250 cells/mm³ for SBP diagnosis. This cutoff has been determined through clinical studies to provide the best balance of sensitivity and specificity for detecting infection, as supported by the management guidelines 1.
Clinical Implications
Patients with SBP require prompt antibiotic treatment, typically with a third-generation cephalosporin, with the choice of antibiotic guided by local resistance patterns, as recommended by the guidelines 1. The high neutrophil count reflects the body's immune response to bacteria that have translocated from the intestines or reached the peritoneal cavity through hematogenous spread.
Key Points
- Neutrophil count >250/mm³ is the gold standard for SBP diagnosis 1.
- Prompt antibiotic treatment is crucial for patients with SBP.
- The choice of antibiotic should be guided by local resistance patterns and protocol 1.
From the Research
Spontaneous Bacterial Peritonitis (SBP) Peritoneal Cell Numbers
- The diagnosis of SBP is based on an elevated polymorphonuclear leukocyte count in the ascites, with a threshold of >0.25 G/L 2.
- A polymorphonuclear cell count of less than 250 per mm3 on serial paracenteses is considered a satisfactory endpoint for antibiotic therapy 3.
- The ascitic fluid polymorphonuclear cell count is the most sensitive test in evaluating for infection, and cultures of the ascitic fluid are helpful in identifying the organism 4.
- The incidence of mortality of the first episode of SBP varies between 10% and 46%, and early antibiotic treatment is warranted 5.
- The reported probability of SBP recurrence one year after the first attack averaged 40 to 69%, and selective intestinal decontamination with norfloxacin can decrease the overall probability of recurrence 5.
Key Findings
- The ascitic fluid polymorphonuclear cell count is a key diagnostic criterion for SBP, with a threshold of >0.25 G/L 2.
- Antibiotic therapy should be initiated promptly once the clinical and laboratory diagnosis of SBP has been made, before the result of AF culture 6.
- Cefotaxime or other third-generation cephalosporins are considered the first-choice empirical antibiotics in the treatment of cirrhotic patients with SBP 6, 4.
- The duration of antibiotic therapy can be determined by serial paracenteses, with a polymorphonuclear cell count of less than 250 per mm3 considered a satisfactory endpoint 3.