From the Guidelines
A neutrophil count of 250 cells/mm³ or greater in ascitic fluid is diagnostic of Spontaneous Bacterial Peritonitis (SBP). This threshold is the established criterion for diagnosing SBP, even in the absence of positive bacterial cultures, as stated in the guidelines on the management of ascites in cirrhosis 1. When a patient with cirrhosis and ascites presents with symptoms such as fever, abdominal pain, or altered mental status, a diagnostic paracentesis should be performed immediately to analyze the ascitic fluid. The neutrophil count is the most important parameter for diagnosis, as bacterial cultures are positive in only about 40% of SBP cases.
Key Points for Diagnosis and Management
- Diagnostic paracentesis should be carried out without delay to rule out SBP in all cirrhotic patients with ascites on hospital admission, especially those with GI bleeding, shock, fever, or other signs of systemic inflammation 1.
- Ascitic fluid culture with bedside inoculation of blood culture bottles should be performed to guide the choice of antibiotic treatment when SBP is suspected 1.
- Empiric antibiotic therapy should be initiated promptly, considering the context of SBP (community-acquired or healthcare-associated), severity of infection, and local bacterial resistance profile 1, 2, 3.
- Third-generation cephalosporins, like cefotaxime or ceftriaxone, are recommended as first-line antibiotics in settings where multi-drug resistant organisms (MDROs) are not prevalent 2, 4, 3.
- Alternative antibiotics, such as amoxicillin/clavulanic acid or ciprofloxacin, may be considered based on local resistance patterns and the specific clinical scenario 2, 4, 3.
- Repeat paracentesis at 48 hours from the start of treatment may be considered to check the efficacy of antibiotic therapy, especially in those with an apparently inadequate response or where secondary bacterial peritonitis is suspected 1, 3.
Considerations for Treatment
The choice of antibiotic should be guided by local resistance patterns and the severity of the infection. In areas with a high prevalence of MDROs or in cases of nosocomial SBP, broader-spectrum antibiotics like meropenem alone or combined with glycopeptides or daptomycin may be necessary 3. The new criteria for the definition of sepsis, namely qSOFA and Sepsis-3, have been validated in patients with cirrhosis and bacterial infections, proving to be more accurate than those related to the systemic inflammatory response syndrome in predicting hospital mortality 3.
Prophylaxis
Patients who have recovered from an episode of SBP should be considered for treatment with norfloxacin, ciprofloxacin, or co-trimoxazole to prevent further episodes of SBP, especially if they are at high risk, as defined by an ascitic protein count <1.5 g/dL 1. Primary prophylaxis should be offered to patients considered at high risk, with the choice of antibiotic guided by local resistance patterns.
From the Research
Ascites Fluid Neutrophil Count for SBP
The ascites fluid neutrophil count is a crucial diagnostic marker for Spontaneous Bacterial Peritonitis (SBP). According to various studies 5, 6, 7, 8, 9, the diagnosis of SBP is based on the analysis of ascites fluid and the presence of a certain number of neutrophil polymorphonuclear (PMN) cells.
Diagnostic Criteria
- The final diagnosis of SBP requires the presence of > 250 mm3 neutrophil polymorphonuclear (PMN) in ascites 5, 6.
- An absolute polymorphonuclear leukocyte count greater than 500/mm3 is highly suggestive of SBP 9.
- The ascitic fluid polymorphonuclear cell count is the most sensitive test in evaluating for infection 8.
Clinical Significance
- A high index of suspicion for SBP should exist in patients with cirrhosis and ascites, and diagnostic abdominal paracentesis can be undertaken with minimal risk 8.
- Empirical therapy is recommended after paracentesis if suspicion for infection exists, and cefotaxime is the best-studied antibiotic for this purpose 8.
- Mortality rates in SBP have declined dramatically, largely due to earlier detection and improved therapy 8.