Spontaneous bacterial peritonitis (SBP) is a bacterial infection of ascites without an identifiable source and is defined as polymorphonuclear leukocytes (PMN) count > 250 cells/mm3 and presence of a single organism in ascitic fluid.

• A potentially fatal but reversible cause of deterioration in patients with advanced cirrhosis and should be suspected in any patient with cirrhosis and ascites.
• Mortality rates increase by 10% for every hour delay in initiating antimicrobial therapy in patients with cirrhosis who are in septic shock.

PATHOPHYSIOLOGY

• Intestinal bacterial overgrowth with subsequent translocation to mesenteric lymph nodes with failure of the immune system in part due to diminished opsonic activity.

CLINICAL PRESENTATION

• Fever (50-75%), abdominal pain (27-72%) or tenderness (30-40%) almost exclusively in context of ascites.
• Can be asymptomatic in small but significant proportions (up to 13%) of patients.

Indications for paracentesis in cirrhotics with ascites include any of the following:

• • at time of admission (consider asymptomatic SBP).
  • change in clinical status.
  • development of lab abnormalities.
  • during episodes of variceal bleeding, prior to antibiotics.
• Fluid PMN count > 250 cells/mm3 is the single best test in diagnosing ascitic fluid infection.
• Ascitic fluid culture should be immediately inoculated at bedside in one aerobic and one anaerobic bottle, prior to initiation of antimicrobial therapy.
• Due to considerable mortality, there should be low threshold to perform diagnostic abdominal paracentesis even in context of coagulopathy.

EXCLUDING SECONDARY BACTERIAL PERITONITIS

• Defined as bacterial infection of ascites with surgically treatable intra-abdominal source of infection (e.g., perforated viscus or intra-abdominal abscess) with PMN count > 250 cells/mm3.

Secondary bacterial peritonitis should be suspected if 2 of 3 of the following on paracentesis fluid analysis:

• • Glucose < 2.8mmol/L.
  • Total protein > 0.62mmol/L.
  • LDH > Upper limit of normal for serum.

If above criteria are met OR polymicrobial ascitic culture, perform upright XR/chest to look for free air and consider CT to investigate for cause of secondary bacterial peritonitis.

OTHER INVESTIGATIONS

• Serum albumin and ascites albumin to confirm portal hypertension (if status unknown).
• Other studies such as ascites fluid pH have limited utility in the diagnosis of SBP.

TREATMENT: ANTIMICROBIAL THERAPY

• Monomicrobial infection with Escherichia coli and gram positives (streptococcus, enterococcus) most common organisms.
• Indications for empiric antimicrobial therapy to be initiated AFTER cultures are obtained if:
  • Fluid PMN > 250 cells/mm3 OR.
  • Clinical signs/symptoms of infection (e.g., fever, abdominal pain/tenderness).
• In most cases, start with Cefotaxime 2g IV q8h.
  • If nosocomial infection, recent hospitalization, or ICU admission, consider piperacillin-tazobactam or carbapenem +/- vancomycin.
• Duration of antimicrobial therapy is 5-7 days.
• Consider repeating diagnostic paracentesis in 48h to assess response.

TREATMENT: ALBUMIN / OTHER CONSIDERATIONS

• Start Albumin 1.5g/kg at day 1 and 1g/kg at day 3.
• Consider holding non-selective beta blockers in patients with SBP who develop hypotension (<65mmHg) or AKI.

SBP PROPHYLAXIS

• In patients with cirrhosis and UGIB, start Ceftriaxone 1g IV q24h until hemorrhage has resolved for maximum of 7 days.
• Antimicrobial prophylaxis should be also considered in patients with cirrhosis who have low protein ascites (<1.5g/L) and severe renal or liver dysfunction (Child-Pugh >9).

1. Serum albumin-ascitic albumin gradient (SAAG)
   -MD+CALC

    

   
   

2. Optimal Management of Cirrhotic Ascites: A review for Internal Medicine Physicians
   Gallo, A. Dedionigi, C. Civitelli, et al. 2020 Dec 31.
   -US National Library of Medicine National Institutes of Health Search database

    

   
   

1. Does this patient have bacterial peritonitis or portal hypertension? How do I perform a paracentesis and analyze the results?
    Wong CL et al. JAMA 2008; 299(10): 1166-78. PMID: 18334692
   -PubMed

   
   

2. Diagnosis, Evaluation and Management of Ascites, Spontaneous Bacterial Peritonitis and Hepatorenal Syndrome 2021: Practice Guidelines by the American Association for the Study of Liver Diseases. 
   Biggins S.W et al. . 2021;74:1014-1048.
   -PubMed

   
   

3. Spontaneous bacterial peritonitis and extraperitoneal infections in patients with cirrhosis.Mattos AA, Wiltgen D, Jotz RF et al.  Annals of Hepatology 2020; 19;451.
   -PubMed