Peritonitis, Spontaneous Bacterial

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

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

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

Laboratory Tests

• Kidney dysfunction, abrupt worsening of kidney function

• Ascitic fluid polymorphonuclear neutrophil (PMN) count of > 250 cells/mcL (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

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

  • 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 more than 250 cells/mcL, antibiotics should be continued for an additional 2–3 days before paracentesis is repeated

  • Should not be used in patients with chronic liver disease because of a high risk of nephrotoxicity

• Intravenous albumin, 1.5 g/kg on day 1 and 1 g/kg on day 3, should be administered to patients at high risk for hepatorenal failure (ie, those with baseline creatinine > 1.0 mg/dL, BUN > 30 mg/dL, or bilirubin > 4 mg/dL)

• Nonselective β-blockers

  • Increase the risk of hepatorenal syndrome in cirrhotic patients with spontaneous bacterial peritonitis

  • Should be discontinued permanently due to adverse impact on cardiac output and renal perfusion in advanced cirrhosis

• Patients with suspected secondary bacterial peritonitis should be given broad-spectrum coverage for enteric aerobic and anaerobic flora with a third-generation cephalosporin and metronidazole

Surgery

• Liver transplant is the most effective treatment for recurrent spontaneous bacterial peritonitis

Follow-Up

• Patients without significant clinical improvement after taking an aminoglycoside for 5 days should undergo repeat paracentesis to assess treatment efficacy

Complications

• Acute kidney failure develops in up to 40% of patients and is a major cause of death

Prognosis

• Mortality rate is 25%, but if recognized and treated early, mortality is < 10%

• Causes of death include liver failure, hepatorenal syndrome, or bleeding complications

Prevention

• Up to 70% of patients who survive an episode of spontaneous bacterial peritonitis will have another episode within 1 year

• Oral once-daily prophylactic therapy has been shown to reduce the rate of recurrent infections to < 20% and is recommended

  • Ciprofloxacin, 500 mg orally once daily

  • Trimethoprim-sulfamethoxazole, one double-strength tablet orally once daily

  • Norfloxacin, 400 mg orally once daily (no longer available in the United States)

• Primary prophylaxis is recommended in patients with no history of spontaneous bacterial peritonitis but who are at increased risk for infection due to low-protein ascites (total ascitic fluid protein < 1.5 g/dL) with impaired kidney function (serum creatinine ≥ 1.2 g/dL) or decompensated cirrhosis (Child-Pugh class C)

• Prophylactic antibiotics are associated with a lower risk spontaneous bacterial peritonitis, hepatorenal syndrome, and mortality

When to Refer

• Patients failing to improve within 3–5 days of initial therapy

• Patients with possible secondary peritonitis, ie, ascites infected by an intra-abdominal infection (appendicitis, diverticulitis)

• Consider secondary peritonitis in patients with

  • Ascites total protein < 1 g/dL, glucose < 50 mg/dL, or ascites lactate dehydrogenase (LD) > upper limit of normal for serum LD

  • Polymicrobial infection

  • High ascitic neutrophil counts (> 10,000/mcL)

When to Admit

• Symptomatic patients require admission for intravenous antibiotics

• Selected asymptomatic patients may be treated with oral antibiotics with close follow-up