- Clinical science
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 for selected high-risk patients. Long-term prophylactic antibiotic therapy is recommended to prevent recurrent infection.
- Spontaneous bacterial peritonitis: : infection of the ascitic fluid in the absence of any focal intraabdominal, surgically treatable source of infection 
- Secondary bacterial peritonitis: inflammation of the peritoneum caused by bacterial infection from a surgically treatable intraabdominal source 
- Most common bacterial infection in patients with cirrhosis. 
- Represents over 30% of bacterial infections among hospitalized patients with cirrhosis. 
- Prevalence among asymptomatic outpatients with decompensated cirrhosis is estimated to be up to 3.5% 
Epidemiological data refers to the US, unless otherwise specified.
Risk factors 
- Additional risk factors in patients with cirrhosis include: 
- Low ascitic fluid protein concentration (< 1.5 g/dL)
- Upper gastrointestinal bleeding
- Prior episodes of SBP
- 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
- Usually a monomicrobial infection; suspect secondary bacterial peritonitis if multiple organisms are demonstrated on ascitic fluid gram stain or culture (see “Secondary bacterial peritonitis” in “Differential diagnoses” section).
- Gram-negative enteric bacteria (e.g., Escherichia coli, Klebsiella spp.) are most common.
- Gram-positive bacteria (e.g., Streptococcus spp., Staphylococcus spp., Enterococcus spp.) are increasing in prevalence.
- Increasing prevalence of fluoroquinolone-resistant and multidrug-resistant bacteria 
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. 
- Obtain 2 sets of blood cultures before the administration of antibiotics.
- Perform paracentesis without delay and before the administration of antibiotics. 
- Rule out secondary bacterial peritonitis (see the section “Differential diagnosis”) and other causes of abdominal pain (see “Acute abdominal pain”). 
- Blood cultures (2 sets)
- Inflammatory markers (e.g., CRP, ESR) may be elevated 
- CBC: potentially leukocytosis
- Liver chemistries: findings consistent with cirrhosis (see “Diagnostics” in “Cirrhosis”); evaluate for worsening hepatic function
- : to evaluate for , ,
Diagnostic paracentesis 
- Patients with cirrhosis and ascites with any of the following: 
- Clinical deterioration or hospital admission 
- Signs of infection (e.g., fever; , hypothermia, tachycardia, tachypnea, shock, leukocytosis, acidosis)
- Gastrointestinal signs or symptoms (e.g., abdominal pain/tenderness, vomiting, diarrhea, , GI bleed)
- Worsening ascites
- Worsening liver and/or renal function
- Patients with cirrhosis and ascites with any of the following: 
- Timing: immediately (ideally before the administration of antibiotics)
Peritoneal fluid analysis
- Cell count and differential: neutrophil count of ≥ 250/mm3 indicates SBP
- Gram stain: limited value; very low sensitivity and high false-positive rates. 
Bacterial cultures: often negative
- Positive cultures not required for diagnosis but should be ordered in every patient suspected of having SBP 
- Definition: a positive ascitic fluid bacterial culture in the presence of ascitic fluid neutrophil count < 250/mm3 that is not associated with a surgically treatable intraabdominal source of infection
- Interpretation: Bacterascites may represent transient bacterial colonization or early 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).
Antimicrobial therapy 
- Indications (presence of any of the following in a patient with cirrhosis and ascites): 
- Most common isolates: Escherichia coli, Streptococcus spp., Staphylococcus spp., and Klebsiella (see “Etiology” section) 
- Risk factors for resistant pathogens include: 
|Empiric antibiotic therapy for spontaneous bacterial peritonitis |
|Patient characteristics||Recommended regimen for patients with cirrhosis|
and no recent beta-lactam antibiotic exposure
suspected resistant pathogen,
and/or recent beta-lactam antibiotic exposure 
Management of bacterascites 
Adjunctive therapy 
- IV albumin supplementation 
- Consider discontinuing beta blockers. 
- Discontinue diuretics. 
- Avoid potentially nephrotoxic medications (e.g., NSAIDs). 
- Consider discontinuing proton-pump inhibitors. 
- Electrolyte repletion
- Analgesics as needed (see “Pain management”)
- Antipyretics as needed
- IV fluids: Use caution in patients who are volume overloaded.
- See “Treatment” and “Complications” in “ ” for other management considerations.
Monitoring and subsequent management 
- Serial abdominal examination
- Repeat paracentesis: not routinely recommended
- Indications (any of the following): 
- The patient does not have advanced cirrhosis (i.e., when SBP is a suspected or confirmed complication of ascites due to causes other than cirrhosis).
- SBP developed in the hospital (i.e., nosocomial infection).
- Recent beta-lactam antibiotic exposure
- Atypical ascitic fluid chemistry: total protein > 1 g/dL, LDH ≥ upper limit of normal for serum, or glucose < 50 mg/dL
- Atypical growth on initial ascitic fluid culture (e.g., polymicrobial)
- Lack of symptom resolution (e.g., ongoing fever and/or abdominal pain) despite antibiotic therapy
- Timing: 48 hours after initiation of antibiotics
- Worsening of signs and symptoms; and/or lack of significant reduction in ascitic fluid neutrophil count (by at least 25%) after initiation of antibiotics; indicates a potential failure of first-line antibiotic therapy and should raise suspicion of secondary bacterial peritonitis (see “Differential diagnosis” section).
- Indications (any of the following): 
- Consider GI/hepatology consult or infectious disease consult.
- Consider referral for a liver transplant evaluation. 
- Obtain blood cultures (2 sets) and routine laboratory studies (CBC, BMP, LFTs, coagulation panel).
- Perform paracentesis and order ascitic fluid analyses (cell count and differential, bacterial culture, total protein, albumin, glucose, LDH).
- Begin .
- Consult infectious disease if concern for healthcare-associated infection or resistant pathogens.
- Consider indications for IV albumin.
- Hold beta blockers, diuretics, and all potentially nephrotoxic medications.
- Provide supportive therapy as needed.
- Consider CT abdomen/pelvis and surgical consult if any concern for secondary bacterial peritonitis (see “Differential diagnosis” section).
- Admit to medical or GI/hepatology service.
- Consider GI/hepatology consult.
Secondary bacterial peritonitis 
- Definition: inflammation of the peritoneum caused by bacterial infection from a surgically treatable intraabdominal source 
- Perforation of an intraabdominal viscous (e.g., duodenal perforation due to a peptic ulcer)
- Translocation of bacteria from an abdominal organ inflammation (e.g., appendicitis, diverticulitis, pancreatitis, intraabdominal abscess)
- Trauma (e.g., penetrating wound)
- Iatrogenic (e.g., surgery, anastomosis insufficiency, invasive procedure)
- Abdominal pain/tenderness
- (e.g., local or diffuse rigidity, rebound tenderness, and/or guarding) 
- Gastrointestinal symptoms (e.g., nausea, vomiting, ileus)
- Signs of infection (e.g., fever, tachycardia, tachypnea, hypotension, leukocytosis, sepsis, shock)
- Worsening or lack of symptom resolution after initiation of antibiotics in a patient initially suspected of having SBP
- Cannot be reliably distinguished from SBP based on the clinical presentation and physical exam alone 
Peritoneal fluid analysis:
- Cell count: neutrophil count of ≥ 250/mm3
- Bacterial culture and/or gram stain: positive
- Chemistries: total protein > 1 g/dL, LDH > upper limit of normal for serum, glucose < 50 mg/dL 
- Other: Carcinoembryonic antigen > 5 ng/mL or alkaline phosphatase > 240 U/L suggests secondary peritonitis with intestinal perforation. 
- Management 
Secondary bacterial peritonitis usually requires imaging and urgent surgical management.
- Spontaneous fungal peritonitis
- Alcoholic hepatitis
- Other common infections in patients with cirrhosis 
- Other conditions that may present with ascites accompanied by fever or abdominal pain 
- See also “Differential diagnosis” in “ ” and “ .”
The differential diagnoses listed here are not exhaustive.
Prophylaxis for SBP 
- Primary prophylaxis: ascitic fluid protein < 1.5 g/dL in patients with either impaired renal function or liver failure
- Secondary prophylaxis: all patients with a previous episode of SBP 
- Short-term prophylaxis in patients with cirrhosis and GI bleeding (see “Complications” in “Portal hypertension”)
- Commonly used agents