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    Spontaneous Bacterial Peritonitis

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    Last Reviewed on Jan 19, 2022
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    By Jim Goulding,Aaron Chan

    Context

    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.

    Diagnostic Process

    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.

    Recommended Treatment

    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).

    Quality Of Evidence?

    Justification

    • Diagnostic value of Fluid PMN count: HIGH. Meta-analysis of prospective studies.
    High

    Diagnostic value of Fluid pH: LOW. Data from prospective studies published over 20 years ago.

    Low
    • Empiric antimicrobial therapy with Cefotaxime: HIGH. Multiple RCTs.
    High
    • Effect of albumin on reducing mortality in SBP: HIGH. Multiple RCTs.
    High
    • Antibiotic prophylaxis to prevent SBP in cirrhosis: LOW. Low-certainty evidence in recent Cochrane review.
    Low

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