What are the criteria for Spontaneous Bacterial Peritonitis (SBP) in patients with ascites?

From the Guidelines

Spontaneous bacterial peritonitis (SBP) in patients with ascites is diagnosed when the ascitic fluid polymorphonuclear leukocyte (PMN) count is ≥250 cells/mm³ in the absence of an intra-abdominal surgically treatable source of infection, as recommended by the most recent guidelines 1. This diagnosis requires a diagnostic paracentesis with analysis of the ascitic fluid.

Key Diagnostic Criteria

• Ascitic fluid PMN count ≥250 cells/mm³
• Absence of an intra-abdominal surgically treatable source of infection
• Positive ascitic fluid bacterial culture, though cultures are negative in approximately 40% of cases despite clinical evidence of infection

Clinical Symptoms and Laboratory Findings

Clinical symptoms of SBP may include:

• Fever
• Abdominal pain
• Altered mental status
• Worsening liver or kidney function Laboratory findings that support the diagnosis include:
• Elevated ascitic fluid total protein
• Low ascitic fluid glucose
• Elevated lactate dehydrogenase compared to serum levels

Patient Management

All patients with ascites admitted to the hospital should undergo diagnostic paracentesis, and those with risk factors such as gastrointestinal bleeding, low ascitic fluid protein (<1.5 g/dL), or previous episodes of SBP should be monitored closely, as recommended by recent guidelines 1. Early diagnosis is crucial as SBP carries a high mortality rate if not promptly treated with appropriate antibiotics. The choice of antibiotic should be guided by local resistance patterns and protocol, with cefotaxime being widely studied but not the only option, as noted in 1. In patients suspected of SBP, cefotaxime at a dose of 2 g every 6-8 hours, or ceftriaxone at a dose of 1 g every 12-24 hours, are recommended by intravenous injection, as suggested in 1. The standard treatment duration is 5 to 10 days, but the treatment duration should vary according to the symptoms and/or results of antimicrobial susceptibility testing, as recommended in 1. Antibiotics should be replaced in accordance with the susceptibility results of bacteria cultured from ascites or blood. Treatment with amoxicillin-clavulanic acid shows similar SBP resolution rates to cefotaxime, and treatment with ciprofloxacin, as noted in 1. Primary prophylaxis should be offered to patients considered at high risk, as defined by an ascitic protein count <1.5 g/dL, as recommended in 1. However, the potential risks and benefits and existing uncertainties should be communicated to patients. 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, as suggested in 1. A second diagnostic paracentesis at 48 hours from the start of treatment to check the efficacy of antibiotic therapy should be considered in those who have an apparently inadequate response or where secondary bacterial peritonitis is suspected, as recommended in 1. Patients presenting with gastrointestinal bleeding and underlying ascites due to cirrhosis should receive prophylactic antibiotic treatment to prevent the development of SBP, as recommended in 1. The choice of antibiotic should be guided by local resistance patterns and protocol. In summary, the diagnosis and management of SBP require a comprehensive approach that includes diagnostic paracentesis, analysis of ascitic fluid, and prompt treatment with appropriate antibiotics, as well as consideration of patient risk factors and local resistance patterns.

From the Research

Diagnostic Criteria for Spontaneous Bacterial Peritonitis (SBP)

The diagnostic criteria for SBP in patients with ascites include:

• Abdominal pain, worsening ascites, fever, or altered mental status in a patient with known liver disease 2
• An ascites absolute neutrophil count (ANC) ≥ 250 cells/mm3 is diagnostic of SBP 2, 3
• Paracentesis 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
• Ultrasound should be used to optimize the paracentesis procedure 2
• Ascitic fluid should be placed in blood culture bottles to improve the culture yield 2
• Leukocyte esterase reagent strips can be used for rapid diagnosis if available 2

Bacteriology of SBP

The bacteriology of SBP includes:

• Gram-negative bacteria, such as Escherichia coli, Klebsiella spp, and Streptococcus spp 4
• Gram-positive bacteria, such as Staphylococcus, Enterococcus, and multi-resistant bacteria 4, 5
• The most common microorganisms identified in SBP are changing, with an increase in gram-positive bacteria and multidrug-resistant bacteria 3, 5

Treatment of SBP

The treatment of SBP includes:

• Third-generation cephalosporins, such as cefotaxime, as a first-line agent 4, 6
• Alternative antibiotics, such as ceftriaxone, ciprofloxacin, and piperacillin-tazobactam, may be considered in certain cases 4, 5, 6
• Albumin infusion is associated with reduced risk of renal impairment and mortality 2, 4
• Selective intestinal decontamination (SID) with norfloxacin may be used as prophylaxis in certain cases 4