Spontaneous Bacterial Peritonitis

Microbiology and Pathogenesis

• SBP develops in patients with severe ascites, usually due to cirrhosis, but also from:

  • CHF

  • Malignancy

  • Lymphedema

• Bacteria enter the peritoneal space through the blood, lymphatic fluid, transluminal passage

• In severe cirrhosis, the RES liver system is often bypassed secondary to shunting, increasing the risk of prolonged bacteremia. The bowel motility is also decreased, resulting in bacterial overgrowth

• Most common pathogens

  • Enteric bowel flora

  • E coli

  • Klebsiella

  • Strep pneumoniae

  • Enterococcus

Clinical Manifestations

• Subtle initial signs and symptoms

• Fever is the most common manifestation, and is usually low grade

• Abdominal pain can be diffuse and constant

  • No guarding

  • The ascites separates the peritoneum, preventing severe inflammatory irritation of the abdominal wall muscles

  • Rebound tenderness in late stages

• AMS, from exacerbated hepatic encephalopathy

• Diarrhea might precede other symptoms

Diagnosis

• Ascitic fluid must be sampled (paracentesis)

  • Needle aspiration

  • Significant bleeding only occurs in less than 1% of patients, despite a high INR in many cases

  • Paracentesis is minimally traumatic and does not require ppx plasma transfusions

  • Samples:

    • (1) Take at least 10 ml of ascitic fluid into a blood culture flask. Change needles before you do this to avoid growing skin flora.

    • (2) Take a second sample into an anticoagulated tube for cell counts

    • (3) total protein, LDH, glucose, amylase, albumin

    • (4) Gram stain

• Interpretation

  • Leukocytes almost always > 300 cells/mm³, with PMN predominance

    • The diagnosis is strongly suggested if the absolute PMN count is over 250/mm³

    • Can test using a UA leuk esterase strip > 21

  • Gram stain is positive in 20-40% of cases

  • The following suggests secondary peritonitis from bowel perforation

    • High total protein

    • High LDH

    • High amylase

    • Low glucose

Treatment

• Empiric antibiotics need to be emergently started after cultures obtained

  • 3rd generation cephalosporin

  • If secondary peritonitis suspected, add metronidazole

  • Treat for 5-10 days depending on response to therapy

Outcome

• Mortality is high (60-70%) due to severe underlying liver disease and the severity of this type of infection

• There is benefit to early diagnosis

• Strongly consider liver transplant for first episode spontaneous peritonitis

Prophylaxis

• Antibiotic ppx is indicated after the first episode

  • Regimens:

    • TMP-SMX 1 ds tab once daily

    • Norfloxacin 400 mg once daily

    • Ciprofloxacin 500 mg once daily

• Stop beta blockers after the first episode

  • Patients may be on NSBB such as propranolol, nadolol, or also carvedilol.

  • Increase mortality, increase rates of hepatorenal syndrome, increase hospitalizations