Spontaneous Bacterial Peritonitis

Infection of ascitic fluid occurring in absence of any evident infective source, which may present as:

SBP is generally a monomicrobial infection. Multiple organisms suggests secondary peritonitis from faecal contamination, which is a surgical disease.

Epidemiology and Risk Factors

Risk factors:

Child-Pugh score is covered under Child-Pugh Score.

  • Previous SBP
  • Invasive devices
  • Hepatic dysfunction
    • Child-Pugh Grade C
    • Variceal bleeding
  • Infection
    • UTI
    • Intestinal bacterial overgrowth

Pathophysiology

Major factors:

  • Ascites is a ready-made, continuously available viable culture medium
  • Immunosuppression secondary to chronic liver disease

Aetiology

Causative organisms:

  • E. coli: 37%
  • K. pneumoniae: 17%
  • Other Gram positives: 14%
  • S. pneumoniae: 12%
  • Other gram negatives: 10%
  • S. viridans: 9%

Clinical Manifestations

Features include:

Asymptomatic in ~10%.

  • Fever: 70%
  • Abdominal pain: 50%
    • Tenderness: 40%
    • Rebound: 10%
  • Confusion
    • Altered level of consciousness: 54%

Diagnostic Approach and DDx

Mortality approaches 80% if an unnecessary laparotomy is performed, so it is vital to distinguish SBP from secondary peritonitis.

Key differentials:

  • Secondary peritonitis
    Indicated by:
    • Peritonism
    • Localising abdominal pain
    • Multiple organisms on Gram stain
    • Failure of antibiotic therapy
    • Ascitic fluid findings
      Two of:
      • Protein >1g/dL
      • Glucose <3mmol/L
      • LDH > ULN of serum LDH

Investigations

Laboratory:

  • Ascitic tap
    Required for diagnosis.
    • Usually low bacterial concentrations of a single organism
    • Consider using a micropuncture kit (e.g. 21G spinal needle) to ↓ risk of continual leak from puncture site
    • 10-20mL should be placed into blood culture bottles to increase yield
    • Diagnostic criteria:
      • WCC >250/mm3
      • Evidence of bacteria
        Usually only one.
    • Paracentesis should be repeated at 48 hours after microbial therapy

Cirrhotic patients with large volume ascites should be tapped on ICU admission irrespective of their admission diagnosis, as ~10% will be complicated with SBP

Turbid Ascites

Imaging:

  • CT
    If concern for secondary peritonitis.

Management

  • Appropriate antibiotics
  • Give 20% albumin
  • Cease nephrotoxins and antihypertensives
  • Consider repeat paracentesis

Specific therapy:

  • Pharmacological
    • Antibiotics
      Choice is contextual, however:
      • Ceftriaxone 2g IV daily
      • Tazocin 4.5g IV TDS
        If resistant species, nosocomial infection, or septic shock.
    • 20% Albumin
      • 1.5g/kg IV, then 1g/kg 48 hours later
      • ↓ AKI
      • Substantial ↓ mortality by ↓ hepatorenal syndrome
  • Procedural
    • Repeat paracentesis
      At 48 hours to evaluate for treatment failure; unnecessary if organism is susceptible and there is clinical improvement.

Supportive care:

  • C
    • Cease β-blockade
      Many patients will be on propranolol for variceal haemorrhage prophylaxis, which will ↓ CO in the septic state.
  • G
    • Feeding
      • ↓ Bacterial translocation
    • Cease PPI
    • Rifaximin 400mg PO TDS

Disposition:

  • Ongoing prophylactic antibiotics
    May be appropriate in high risk patients; agents include:
    • Rifaximin
    • Norfloxacin
    • Ciprofloxacin

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

  • B
    • Pleural effusion
      • May occur when there is communication betwen the abdomena nd pleura
      • Thoracocentesis is indicated for:
        • Respiratory failure
        • Clinical suspicion of empyema

Prognosis

Features associated with ↑ mortality include:

  • Resistant organism

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.