Description

• Definition: inflammation of the peritoneum
• Classification:
  • Aseptic: chemical irritation or systemic inflammation of peritoneum
  • Bacterial: infection of peritoneal fluid
• Bacterial peritonitis types:
  • Primary/spontaneous bacterial peritonitis (SBP): infection of ascitic fluid in the absence of an intra-abdominal source
  • Secondary bacterial peritonitis: infection of ascitic fluid from a detectable intra-abdominal source
    • Secondary bacterial peritonitis can be further classified as either perforation peritonitis or nonperforation peritonitis.
  • Tertiary bacterial peritonitis: >48 hours of infection despite source control
  • Peritoneal dialysis–associated peritonitis
  • Perforated appendicitis and chronic peritoneal dialysis are the most common cause leading to acute peritonitis in children.

Epidemiology

Incidence

• In cirrhotic patients with ascites, the annual incidence of SBP is 10–25%.
• 25–75% of patients with secondary bacterial peritonitis progress to tertiary peritonitis.

Prevalence

• SBP: In asymptomatic patients with cirrhosis and ascites, the prevalence of SBP is <4% in outpatients. Nosocomial rates are 10%.
• In patients with cirrhosis and ascites, 5% of peritonitis is secondary.
• Secondary peritonitis is the most common cause of sepsis in surgical ICU patients.
• PD peritonitis is the primary reason for switching from PD to hemodialysis (HD).
• PD peritonitis in children is more common than in adults.

Etiology and Pathophysiology

• Mechanism
  • SBP:
    • Bacterial translocation via lymphatic spread through mesenteric lymph nodes
    • Often develops in the setting of large-volume ascites in patients with advanced cirrhosis
    • Cirrhotic patients have:
      • Alterations to gut microbiota with higher prevalence of pathogenic organisms
      • Small intestinal bacterial overgrowth (SIBO) and increased intestinal mucosal permeability to bacteria
      • Decreased cellular and humoral immunity limiting peritoneal bacterial clearance
  • Secondary:
    • Translocation of bacteria from inflamed or perforated intraperitoneal (IP) organs or introduction of bacterial through instrumentation
  • Tertiary: evolves from secondary peritonitis
  • PD peritonitis:
    • Contamination with pathogenic skin flora during exchanges or exit-site infection
• Microbiology
  • SBP. Most cases (>90%) of SBP are monomicrobial.
    • Most common gram-negative pathogens are Escherichia coli (33%) and Klebsiella spp. (8%).
    • Most common gram-positive pathogens are Streptococcus spp. (15%) and Staphylococcus aureus (13%).
  • Secondary: perforation of a viscus, small bowel strangulation, necrotizing pancreatitis. Organism depends on cause of peritonitis; gram-positive organisms more common with upper GI pathology, whereas gram-negative organisms more common with lower GI pathology. Common species include E. coli, Klebsiella, Proteus, Streptococcus, Enterococcus, Bacteroides, and Clostridium.
  • PD peritonitis is most commonly due to Staphylococcus epidermidis and S. aureus.

Risk Factors

• SBP: advanced cirrhosis with ascites, malnutrition, upper GI bleed, PPI usage, and prior SBP
  • Acid suppression (most commonly with PPIs) promotes gut bacterial growth and translocation.
  • 70% of SBP cases are in patients with Child-Pugh class C cirrhosis.
  • Low ascites protein (<1.0 g/dL) increases risk.
• Secondary:
  • Helicobacter pylori or NSAIDs-induced ulcers, vascular disease causing bowel ischemia, alcohol abuse causing pancreatitis, trauma, or IBD causing bowel perforation
• PD peritonitis:
  • Nonsterile technique
  • Recent instrumentation

General Prevention

• SBP prophylaxis decreases mortality in patients at high risk (e.g., ascitic fluid protein concentration <1.0 g/dL, esophageal varices, or history of previous SBP).
  • Antibiotics include norfloxacin, ciprofloxacin, TMP/SMZ PO, ceftriaxone IV.
  • Patients with cirrhotic ascites who have low ascitic fluid protein (<1.5 g/dL), renal impairment (creatinine ≥1.2 mg/dL, BUN ≥25 mg/dL, serum sodium [Na] ≤130 mEq/L), or liver failure (Child-Pugh score ≥9 and serum bilirubin ≥3 mg/dL) should also receive SBP prophylaxis.
• Limit use of PPIs.
• PD peritonitis:
  • Sterile techniques
  • Antibiotic prophylaxis prior to selected procedures

Commonly Associated Conditions

SBP almost always occurs in the setting of decompensated cirrhosis.