20: Spontaneous Bacterial Peritonitis



Overall Bottom Line


  • SBP is observed predominantly in patients with advanced cirrhosis.
  • Gram-negative aerobic bacteria are causative in approximately 80% of patients, anaerobic bacteria occur in no more than 5% of patients, but the prevalence of multidrug resistant organisms is increasing.
  • Diagnostic paracentesis with ascitic fluid analysis (PMN count and culture) is the cornerstone of diagnosis.
  • Primary and secondary prophylaxis improves survival.
  • Treatment (third generation cephalosporins are first line antibiotics) leads to resolution of SBP in 70–90% of patients.
  • Early diagnosis and treatment have reduced in-hospital mortality from approximately 80% to 15–20%.






Section 1: Background



Definition



  • SBP is a life-threatening infection of ascites in the absence of an intra-abdominal source of infection and with no obvious source of bacteria.


Epidemiology



  • SBP is observed predominantly in patients with advanced cirrhosis.
  • The prevalence of SBP in outpatients is 1.5–3.5% and approximately 15–20% in hospitalized patients.
  • SBP occurs in between 25% and 65% of cirrhotic patients with acute GI bleeding.


Etiology



  • Gram-negative aerobic bacteria is most common (80% of cases; E. coli > Klebsiella species).
  • Gram-positive cocci, mainly Streptococcus species (S. pneumoniae) occur in 20% of cases.
  • Anaerobic bacteria occur in <5% of patients.
  • Ninety percent of all SBP cases are monomicrobial.
  • Epidemiology of bacterial infections differs between community-acquired (Gram-negative infections predominate) and nosocomial infections (Gram-positive infections predominate).
  • Microbiology of SBP is changing with an increasing prevalence of MDR organisms. Suspect MDR organisms if:

    • SBP is nosocomial.
    • The patient was in hospital recently.
    • The patient had intestinal decontamination.


Pathogenesis



  • Multifactorial, not well understood.
  • Dysfunction of the immune system in cirrhosis.
  • Activity of the RES-system (chemotaxis, phagocytosis, intracellular killing) impaired.
  • Deficient phospholipase C activity in blood neutrophils.
  • Increased intestinal permeability.
  • Bacterial overgrowth and translocation of intestinal micro-organisms.
  • Endotoxemia.
  • Reduced levels of antibacterial substances in ascites (e.g. opsonins, complement components).


Risk factors



  • The risk of SBP is increased in cirrhotic patients with the following conditions:

    • GI bleeding.
    • Low total protein concentration (<1–1.5 g/dL) in ascites.
    • Severe liver dysfunction.
    • History of previous SBP.
    • Use of proton pump inhibitors.


Section 2: Prevention



  • Primary prophylaxis is restricted to patients with high risk of SBP.
  • Third generation cephalosporins are first line antibiotics in patients with acute GI bleeding.
  • Fluoroquinolones may be used in patients with low total protein content in ascites.
  • Primary prophylaxis improves survival.
  • Whether prophylaxis should be given intermittently or continuously remains unsettled.


Screening



  • A diagnostic paracentesis should be performed:

    • In all cirrhotic patients with newly formed ascites.
    • In any patient with cirrhosis and ascites on hospital admission.
    • In patients with cirrhosis and ascites who develop compatible symptoms or signs of peritonitis (e.g. abdominal pain, fever).
    • In any patient with cirrhosis and ascites with worsening renal, liver or mental function/hepatic encephalopathy without an obvious cause (see Chapter 19).


Primary prevention



  • Primary prophylaxis should be restricted to patients at high risk of SBP, i.e. those with:

    • Low total protein content in ascites (1–1.5 g/dL), and/or
    • Acute GI hemorrhage.

  • Patients with acute GI bleeding and severe liver disease:

    • Ceftriaxone 1–2 g IV once a day for 3–4 days. May be switched to
    • Norfloxacin 400 mg PO twice a day after bleeding has been controlled.

  • Patients with acute GI bleeding and less severe liver disease:

    • Norfloxacin 400 mg PO once to twice a day or
    • Ciprofloxacin 500 mg PO twice a day or 750 mg PO once weekly.

  • Patients without GI bleeding with low total protein (<1–1.5 g/dL) in ascites:

    • Norfloxacin 400 mg PO once a day for 12 months.

  • Whether prophylaxis should be given intermittently or continuously currently is unsettled.


Secondary prevention



  • Patients recovering from one episode of SBP should receive long-term secondary prophylaxis with:

    • Norfloxacin 400 mg PO once a day (or another quinolone) or
    • Co-trimoxazole (TMP/SMX) 1 double-strength tablet PO once a day, 5 days per week.

  • Secondary prophylaxis should be continued until the disappearance of ascites or until liver transplantation.
  • Long-term secondary prophylaxis will result in a:

    • Change of bacterial spectrum towards Gram-positive cocci as well as
    • Emergence of quinolone resistant Gram-negative organisms.

  • Patients who develop SBP on prophylactic quinolones respond as well to third generation cephalosporins as patients not on prophylaxis.


Section 3: Diagnosis






Clinical Pearls


  • Clinical findings are unreliable and may be misleading.
  • The diagnosis of SBP is based on the results of ascitic fluid analysis:

    • Neutrophil cell count >250/mm3 (>0.25 × 109/L).
    • Positive culture.





Differential diagnosis
















Differential diagnosis Features
Secondary bacterial peritonitis
due to intestinal perforation		 Suspect secondary bacterial peritonitis in patients with:


  • Polymicrobial ascites with very high ascitic PMN count (>5000 PMN/mm3), and/or
  • High ascitic protein concentration or
  • Inadequate response to therapy (failure of neutrophil count to fall after 48 hours of antibiotic therapy)
Peritoneal tuberculosis Culture-negative peritonitis; sensitivity of ascites smear for mycobacteria is 0%, that of ascites culture is approximately 50%
Peritoneal carcinomatosis Culture-negative peritonitis; if three still warm ascites samples are examined without delay the sensitivity of cytological examination in diagnosing peritoneal carcinomatosis amounts to >90%


Typical presentation



  • The clinical signs and symptoms of SBP may be subtle and range from:

    • Asymptomatic, to
    • Fever, abdominal pain, abdominal tenderness, altered mental status (50–60% of patients),
    • Diarrhea, paralytic ileus, hypotension, hypothermia (≤50% of patients).

Tags:
Aug 12, 2016 | Posted by in GASTROENTEROLOGY | Comments Off on 20: Spontaneous Bacterial Peritonitis

Full access? Get Clinical Tree
Get Clinical Tree app for offline access