What are the diagnostic studies for Spontaneous Bacterial Peritonitis (SBP)?

From the Guidelines

Diagnostic paracentesis should be carried out without delay to rule out Spontaneous Bacterial Peritonitis (SBP) in all cirrhotic patients with ascites on hospital admission, and ascitic neutrophil count >250/mm3 remains the gold standard for the diagnosis of SBP. The diagnostic studies for SBP include:

• Diagnostic paracentesis to rule out SBP in all cirrhotic patients with ascites on hospital admission 1
• Ascitic neutrophil count >250/mm3 to diagnose SBP, which can be performed by manual microscopy or automated counts based on flow cytometry 1
• Ascitic fluid culture with bedside inoculation of blood culture bottles to guide the choice of antibiotic treatment when SBP is suspected 1
• A second diagnostic paracentesis at 48 hours from the start of treatment to check the efficacy of antibiotic therapy in patients who have an apparently inadequate response or where secondary bacterial peritonitis is suspected 1 Key considerations in the diagnosis and management of SBP include:
• Immediate empirical antibiotic therapy should be determined with due consideration of the context of SBP, severity of infection, and local bacterial resistance profile 1
• Patients presenting with gastrointestinal bleeding and underlying ascites due to cirrhosis should receive prophylactic antibiotic treatment to prevent the development of SBP 1
• 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 1

From the Research

Diagnostic Studies for Spontaneous Bacterial Peritonitis (SBP)

The diagnostic studies for SBP include:

• Paracentesis, which is the diagnostic modality of choice and should be performed in any patient with ascites and concern for SBP or upper gastrointestinal bleeding, or in those being admitted for a complication of cirrhosis 2
• Ascitic fluid analysis, which includes an absolute neutrophil count (ANC) ≥ 250 cells/mm3, which is diagnostic of SBP 2
• Ultrasound, which should be used to optimize the paracentesis procedure 2
• Leukocyte esterase reagent strips, which can be used for rapid diagnosis if available 2
• Ascitic fluid culture, which should be placed in blood culture bottles to improve the culture yield 2

Key Findings

Key findings from the studies include:

• SBP is commonly due to Gram-negative bacteria, but infections due to Gram-positive bacteria and multidrug resistant bacteria are increasing 2
• The typical presentation of SBP includes abdominal pain, worsening ascites, fever, or altered mental status in a patient with known liver disease 2
• A high index of suspicion should lead to early diagnostic paracentesis and ascitic fluid analysis 3
• The treatment of SBP involves the use of non-nephrotoxic broad-spectrum antibiotics expected to cover the typical bacterial flora associated with SBP 3

Diagnostic Criteria

The diagnostic criteria for SBP include:

• An ascitic fluid ANC ≥ 250 cells/mm3 2
• The presence of bacteria in the ascitic fluid, as confirmed by culture or Gram stain 3, 2
• The presence of symptoms such as abdominal pain, fever, or altered mental status in a patient with known liver disease 3, 2