Peritonitis, Spontaneous Bacterial

Key Features

Essentials of Diagnosis

• A history of chronic liver disease and ascites

• Fever and abdominal pain

• Peritoneal signs uncommonly encountered on examination

• Ascitic fluid neutrophil count > 250 white blood cells (WBC)/mcL (0.25 × 10⁹/L)

General Considerations

• Occurs with few exceptions in patients with ascites caused by chronic liver disease

• Affects ~20–30% of cirrhotic patients

• Most common pathogens are enteric gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae) or gram-positive bacteria (Streptococcus pneumoniae, viridans streptococci, Enterococcus)

• Patients with ascitic fluid total protein of < 1 g/dL are at increased risk

Clinical Findings

Symptoms and Signs

• Symptoms in 80–90%; asymptomatic in 10–20%

• Fever and abdominal pain present in two-thirds

• Change in mental status due to precipitation or exacerbation of hepatic encephalopathy

• Signs of chronic liver disease with ascites

• Abdominal tenderness in < 50%

Differential Diagnosis

• Secondary bacterial peritonitis, eg, appendicitis, diverticulitis, perforated peptic ulcer, perforated gallbladder

• Peritoneal carcinomatosis

• Pancreatic ascites

• Tuberculous ascites

Diagnosis

Laboratory Tests

• Kidney dysfunction, abrupt worsening of kidney function

• Ascitic fluid polymorphonuclear neutrophil (PMN) count of > 250 cells/mcL (0.25 × 10⁹/L) (neutrocytic ascites) or percentage of PMNs > 50–70% of the ascitic fluid WBC count is presumptive evidence of bacterial peritonitis

• Ascitic fluid Gram stain and reagent strips are insensitive

• Ascitic fluid cultures should be obtained by inoculating blood culture bottles at the bedside

• 10–30% of patients with neutrocytic ascites have negative ascitic bacterial cultures ("culture-negative neutrocytic ascites"), but are presumed nonetheless to have bacterial peritonitis and treated empirically

• Blood cultures occasionally are positive, which helps identify the organism when ascitic fluid cultures are negative

Imaging Studies

• Abdominal CT imaging should be obtained to look for evidence of an intra-abdominal source of infection

Diagnostic Procedures

• Abdominal paracentesis

Treatment

Medications

• Empiric therapy should be initiated with a third-generation cephalosporin

  • Cefotaxime, 2 g intravenously every 8–12 hours

  • Ceftriaxone, 1–2 g intravenously every 24 hours

  • Combination β-lactam/β-lactamase agent, such as ampicillin/sulbactam 2 g/1 g intravenously every 6 hours

• Aminoglycosides

  • Recommended duration of antibiotic is 5–10 days or until the ascites fluid PMN count decreases to < 250 cells/mcL (0.25 × 10⁹/L)

  • If the ascitic neutrophil count has not decreased by 25%, antibiotic coverage should be adjusted (guided by culture and sensitivity results, if available) and secondary causes of peritonitis excluded

  • If the ascitic PMN count has decreased but remains > 250 cells/mcL (0.25 × 10⁹/L), antibiotics should be continued for an additional 2–3 days before ...