Spontaneous bacterial peritonitis (SBP) is an inflammatory reaction of the peritoneum secondary to the presence of bacteria or other microorganisms. More specifically, SBP is defined as an ascitic fluid infection without an evident intraabdominal surgically treatable source occurring primarily in patients with advanced cirrhosis of the liver.

Primary peritonitis

SBP

Peritonitis, spontaneous bacterial

• Acute fever with accompanying abdominal pain/ascites, nausea, vomiting, diarrhea.
• In cirrhotic patients, presentation may be subtle with a low-grade temperature (100° F [37.8° C]) with or without abdominal abnormalities.
• In patients with ascites, a heightened degree of awareness is necessary for detection.
• Jaundice and encephalopathy.
• Deterioration of mental status and/or renal function.
• Table E1 summarizes symptoms and signs of ascetic fluid infection.

• Escherichia coli
• Klebsiella pneumoniae
• Streptococcus pneumoniae
• Streptococcus and Enterococcus spp.
• Staphylococcus aureus
• Anaerobic pathogens: Bacteroides, Clostridium organisms
• Other: Fungal, mycobacterial, viral

• Appendicitis (in children)
• Perforated peptic ulcer
• Secondary bacterial peritonitis
• Peritoneal abscess
• Splenic, hepatic, or pancreatic abscess
• Cholecystitis
• Cholangitis

Paracentesis and ascitic fluid analysis will confirm diagnosis (see “Laboratory Tests”).

Ascitic fluid analysis reveals the following:

• Cell count with an absolute polymorphonuclear cell count >250/mm³
• Presence of bacteria on Gram stain
• pH <7.31
• Lactic acid >32 mg/dl
• Protein <1 g/dl
• Glucose >50 mg/dl
• Lactate dehydrogenase <225 μU/ml
• Positive culture of peritoneal fluid
• Measurement of the serum/ascites/albumin gradient: The serum/ascites/albumin gradient indirectly measures portal pressure. The albumin concentration of ascitic fluid and serum must be obtained on the same day. The ascitic fluid value is subtracted from the serum value to obtain the gradient. If the difference (not a ratio) is >1.1 g/dl, the patient has portal hypertension, with 97% accuracy. If the difference is <1.1 g/dl, portal hypertension is not present. The majority of patients with SBP have portal hypertension as a result of cirrhosis

• Abdominal ultrasound: If there is clinical difficulty in performing paracentesis
• CT scan: To rule out secondary peritonitis (if indicated) and to exclude abscess, mass

• Cefotaxime (2 g IV q8h) or ceftriaxone (2 g IV q24h). Alternative agents include ticarcillin-clavulanate, piperacillin-tazobactam, cefoxitin, and meropenem (for multidrug resistant gram-negative rods). Continue therapy for 5 to 7 days. Repeat diagnostic paracentesis can be done at day 2. Repeat paracentesis at 48 hr will demonstrate a significant decrease in polymorphonuclear count in patients with SBP. If ascites PMN count decreases by at least 25% at day 2, IV therapy can be switched to PO (levofloxacin 500 to 750 mg qd) to complete 7 days of therapy if organisms are susceptible.
• IV albumin (1.5 g/kg of body weight upon initial diagnosis and 1 g/kg of albumin on day 3) if BUN >30 mg/dl, serum creatinine >1 mg/dl, bilirubin >4 mg/dl.

• Ciprofloxacin 500 mg PO qd or levofloxacin 250 mg PO qd.
• Alternative therapy: TMP-SMX one double-strength tablet PO qd.
• Rifaximin 1200 mg a day was shown in a recent study to be superior to norfloxacin.
• Prophylaxis should be continued until disappearance of ascites or until liver transplantation.

The overall mortality rate from an episode of SBP is 20%, and following an episode, the 1-yr mortality rate approaches 70%. Patients that develop SBP should be considered for liver transplantation.

• Renal failure is a major cause of morbidity in cirrhotic patients with SBP. The use of IV albumin (1.5 g/kg at the time of diagnosis and 1 g/kg on day 3) may lower the rate of renal failure and mortality in patients with SBP.
• The criteria for the diagnosis of SBP require that abdominal paracentesis be performed and ascitic fluid be analyzed before a diagnosis of SBP can be made.
• Culturing ascitic fluid as if it were blood (with bedside inoculation of at least 10 ml of ascitic fluid directly into blood culture bottles at the bedside) has been shown to significantly increase the culture positivity of the ascitic fluid in the 80% to 100% range.
• Avoid therapeutic paracenteses during active infection.
• Positive blood cultures in an individual with ascites require exclusion of a peritoneal source by paracentesis.
• Follow-up paracentesis is indicated only in selected cases (worsening clinical status, nosocomial SBP, infection with atypical organism, recent β-lactam exposure).
• All patients with ascites and upper gastrointestinal hemorrhage should receive prophylaxis for SBP with IV ceftriaxone for as long as 7 days.¹