Spontaneous bacterial peritonitis

Pathophysiology - Leaky Gut, Angry Bug

• Portal Hypertension & Cirrhosis → Gut edema, ↓ motility, & small intestinal bacterial overgrowth (SIBO).
• "Leaky Gut": ↑ Intestinal permeability allows bacteria to cross the gut wall (translocation).

• "Angry Bug" is a misnomer: The host is compromised, not the bug more virulent.
  • Most common organisms: E. coli (~70%), Klebsiella, Strep. pneumo.

⭐ Ascitic fluid with low total protein (< 1 g/dL) has poor opsonic activity (↓ opsonins like complement), significantly increasing SBP risk.

Diagnosis - Tapping the Abdomen

• Indication: Perform diagnostic paracentesis in any patient with cirrhosis and ascites upon hospital admission, or with signs of infection (fever, pain) or clinical deterioration.
• Core Analysis:
  • Cell Count: An ascitic fluid absolute polymorphonuclear (PMN) leukocyte count of ≥250 cells/mm³ is the primary diagnostic criterion.
  • Culture: Essential for pathogen identification and sensitivity testing. Gram stain is low-yield.
  • SAAG: Serum-Ascites Albumin Gradient. A value > 1.1 g/dL is consistent with portal hypertension.

⭐ High-Yield: Inoculating ascitic fluid into blood culture bottles at the bedside significantly increases the culture yield (~80%) compared to conventional sterile containers.

Management - Bug Juice Cocktails

• Empiric Antibiotics: Initiate immediately after paracentesis if SBP is suspected. Do not wait for culture results.
  • Primary targets: E. coli, Klebsiella pneumoniae, Streptococcus pneumoniae.
• IV Albumin Adjunct: Co-administer with antibiotics.
  • Dosing: 1.5 g/kg on day 1, then 1.0 g/kg on day 3.
• Prophylaxis (Secondary): To prevent recurrence.
  • Daily Norfloxacin, Ciprofloxacin, or TMP-SMX.

⭐ IV albumin co-administration is critical; it significantly reduces the incidence of hepatorenal syndrome and improves short-term survival in patients with SBP.

Prophylaxis - Keeping Bugs at Bay

• Primary Prophylaxis: For high-risk patients without prior SBP.

  • Indicated if ascitic fluid protein is < 1.5 g/dL, plus either:
    • Advanced liver failure (Child-Pugh score ≥ 9 & bilirubin ≥ 3 mg/dL)
    • Renal dysfunction (Cr ≥ 1.2, BUN ≥ 25, or Na ≤ 130)

• Secondary Prophylaxis: Lifelong prevention for any patient who has survived an episode of SBP.

• Common Regimens:

  • Daily oral ciprofloxacin or norfloxacin.
  • Daily trimethoprim-sulfamethoxazole (TMP-SMX).

⭐ Patients with cirrhosis and an upper GI bleed are given short-term (e.g., 7 days) ceftriaxone prophylaxis due to a very high risk of developing SBP.

• SBP is an infection of pre-existing ascitic fluid without an evident intra-abdominal source, typically in patients with cirrhosis.
• Suspect in any patient with cirrhosis and ascites presenting with fever, abdominal pain, or altered mental status.
• Diagnosis is confirmed by paracentesis showing an ascitic fluid PMN count ≥ 250 cells/mm³.
• The most common pathogens are gram-negative bacteria, especially E. coli.
• Third-generation cephalosporins (e.g., cefotaxime, ceftriaxone) are the empiric treatment of choice.