Spontaneous Bacterial Peritonitis (SBP)

Bailey DeCoursey

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Background

• Infection of ascitic fluid without evidence of a surgical intra-abdominal source

• Present in approximately ⅓ of patients with cirrhosis who are hospitalized

• Presentation: fever, abdominal pain, encephalopathy, renal failure, acidosis, and/or leukocytosis

• Pathophysiology: Combination of GI bacterial flora overgrowth, reduced liver protein production (low complement levels), impaired phagocytic cell function leading to inability to clear pathogens

Evaluation

• Any pt with cirrhosis and ascites who is admitted should have diagnostic para to r/o SBP. Delaying paracentesis > 12 hours is associated with a 2.7-fold increase in mortality.

  • Obtain cell count with diff
  • Calculate the PMNs: total nucleated cells x % neutrophils.
  • PMN > 250 cells is diagnostic of SBP. If there are greater than 100k RBCs, you should correct for them: for every 250 RBCs, subtract 1 PMN

• A positive ascitic bacterial culture with PMN <250 is called bacterascites and asymptomatic patients with bacterascites should NOT receive antibiotics as it is likely a contaminant (however, repeat paracentesis should be performed to exclude progression to SBP). You will also frequently see culture-negative SBP (neutrocytic ascites) which SHOULD be treated (see below).

Management

• Immediately start empiric antibiotics

  • Guidelines recommend cefotaxime IV 2gm q8 hours x 5 days, but we commonly use ceftriaxone IV 2g q24h for 5-7 days at VUMC and Nashville VA
    • Most common culprits (E. coli, Klebsiella, streptococcal species, staphylococcal species)
    • If SBP developed with recent hospital admission (90 days), recent exposure to BSA, diagnosed >48 hours of admission, or with sepsis, should give zosyn ± vanc if prior infection or positive swab for MRSA. Daptomycin should be added with hx of VRE infection instead of vanc.
    • Finally, in patients with current or recent exposure to zosyn consider meropenem for MDR coverage.

• IV albumin 1.5 g/kg on day 1 and 1g/kg on day 3

• NSBB do not need to be discontinued in patients with SBP unless hypotensive (mean arterial pressure <65mmHg). If stopped, the timing of re-initiation is based on recovery of blood pressure

• PPI’s ↑ risk for SBP in pts with cirrhosis, and should be reviewed for appropriateness

• Repeat diagnostic paracentesis two days after antibiotics initiated

  • If <25% decrease in PMNs, antibiotics should be broadened. Consider secondary bacterial peritonitis.

• Prophylaxis:

  • GI bleed: ceftriaxone 1g dailyàciprofloxacin 500mg BID (preferred) or Bactrim one DS tablet BID x 5-7 days

• Outpatient lifelong ppx, indications:

  • Prior SBP
  • Ascitic protein <1.5 AND
    • Child Pugh >9 and bilirubin >3 OR
    • Renal dysfunction (Cr >1.2, Na <130, or BUN >25)
  • Preferred: Bactrim DS tab daily or ciprofloxacin 500mg daily
  • Alternatives: cefdinir 300mg daily, Augmentin 875/125 daily

• If suspicion is high for secondary bacterial peritonitis:

  • Examine serum-ascites albumin gradient (SAAG). SBP develops in pts with portal hypertension, defined by SAAG > 1.1 g/dL. SBP is unlikely if SAAG is < 1.1 g/dL.
  • While not particularly sensitive, an ascitic leukocyte count of 5-10k should prompt consideration of secondary peritonitis
  • Amylase from fluid can also be helpful to point towards pancreatic ascites, while bilirubin can indicate gallbladder perforation.
  • Peritoneal fluid CEA and alkaline phosphatase can additionally help identify hollow viscus injury.
  • Evaluate with cross-sectional imaging and surgical consultation as appropriate
  • Runyon’s Criteria to distinguish, requires ⅔ criteria below (protein, glucose, LDH)

	Spontaneous	Secondary
Protein (g/dL)	<1	>1
Glucose (mg/dL)	≥50	<50
LDH (U)	Elevated, but < 225	>225
Organisms	0-1	Polymicrobial