Spontaneous bacterial peritonitis

Last updated: September 13, 2023

Summarytoggle arrow icon

Spontaneous bacterial peritonitis (SBP) is a bacterial infection of ascitic fluid that occurs in the absence of an identifiable intraabdominal source of infection. It is the most common bacterial infection and a leading cause of hospital admission and mortality among patients with cirrhosis. Enteric gram-negative bacteria (e.g., E. coli, Klebsiella spp.) have historically been the most common isolates; however, gram-positive, fluoroquinolone-resistant, and multidrug-resistant bacteria are increasingly common. SBP may manifest with fever, abdominal pain, and/or altered mental status, but some patients are asymptomatic at presentation. Diagnosis is based on the finding of elevated ascitic fluid neutrophil count (≥ 250/mm3) without an intraabdominal surgically-treatable source of infection. Timely antibiotic administration is the mainstay of therapy. Empiric antibiotic choice depends on the setting of infection (i.e., community-acquired infection vs. healthcare-associated infection), previous antibiotic exposure, and local bacterial susceptibility patterns. IV albumin supplementation is used as adjunctive therapy. Long-term prophylactic antibiotic therapy is recommended to prevent recurrent infection.

Definitiontoggle arrow icon

  • Spontaneous bacterial peritonitis: : infection of the ascitic fluid in the absence of any focal intraabdominal, surgically treatable source of infection [1]
  • Secondary bacterial peritonitis: inflammation of the peritoneum caused by bacterial infection from a surgically treatable intraabdominal source [2]

Epidemiologytoggle arrow icon

  • Most common bacterial infection in patients with cirrhosis. [3]
  • Represents over 30% of bacterial infections among hospitalized patients with cirrhosis. [4]
  • Prevalence among asymptomatic outpatients with decompensated cirrhosis is estimated to be up to 3.5% [5]

Epidemiological data refers to the US, unless otherwise specified.

Etiologytoggle arrow icon

Risk factors [3]

SBP in adults occurs almost exclusively in patients with cirrhosis and ascites. [6]

Pathophysiology [3][7]

  • Bacterial translocation from the intestinal lumen to mesenteric lymph nodes ; spread to systemic and portal circulation colonization and subsequent infection of ascitic fluid
  • Contributing factors related to underlying portal hypertension and cirrhosis:
    • Intestinal dysmotility
    • Bacterial overgrowth
    • Altered intestinal permeability
    • Systemic immune dysfunction

Microbiology [3][7]

SBP is typically a monomicrobial bacterial infection. The presence of multiple organisms on ascitic fluid gram-stain or culture should raise suspicion for secondary bacterial peritonitis.

Clinical featurestoggle arrow icon

Symptoms and signs of SBP may be subtle or absent.

Diagnosticstoggle arrow icon

SBP is diagnosed when the ascitic fluid neutrophil count is ≥ 250/mm3, with or without positive ascitic fluid bacterial cultures, and in the absence of another intraabdominal source of infection. SBP is often asymptomatic and a high index of suspicion is essential in any patient with cirrhosis and ascites. [3]

Approach [10][11]

Laboratory studies

Peritoneal fluid analysis [3][10][11]

  • Obtained via diagnostic paracetensis
  • When indicated, perform this procedure as soon as possible (ideally before the administration of antibiotics).
  • See “Paracentesis” for further details on indications, contraindications, steps, troubleshooting, and complications of this procedure.

Indications for diagnostic paracentesis in SBP

Patients with cirrhosis and ascites with any of the following: [2][11]

Peritoneal fluid analysis in SBP

SBP is diagnosed when the ascitic fluid neutrophil count is ≥ 250/mm3 in the absence of another intraabdominal source of infection. The diagnosis of SBP does not require positive ascitic fluid cultures.


Imaging tests are not required for diagnosis but may be indicated in patients with new-onset or worsening ascites (see ”Diagnostics” in “Cirrhosis”) or if secondary bacterial peritonitis is suspected (see “Differential diagnosis” section).

Treatmenttoggle arrow icon

Antimicrobial therapy [10][11]

Empiric antibiotic therapy

Empiric antibiotic therapy for spontaneous bacterial peritonitis [10][11]
Patient characteristics Recommended regimen for patients with cirrhosis

Community-acquired infection

AND no recent exposure to broad-spectrum antibiotics

Healthcare-associated infection,

suspected resistant pathogen,

AND/OR recent exposure to broad-spectrum antibiotics [10]

Management of bacterascites [10][11]

Empiric antibiotics are not indicated for asymptomatic patients with bacterascites.

Adjunctive therapy [10][11]

Supportive therapy

Monitoring and subsequent management [10][11]

Acute management checklisttoggle arrow icon

Differential diagnosestoggle arrow icon

Secondary bacterial peritonitis [2][11][13]

Secondary bacterial peritonitis usually requires imaging and urgent surgical management.


The differential diagnoses listed here are not exhaustive.

Complicationstoggle arrow icon

We list the most important complications. The selection is not exhaustive.

Preventiontoggle arrow icon

Prophylaxis for SBP [2][11]

Referencestoggle arrow icon

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