Spontaneous bacterial peritonitis

See Peritoneal dialysis-associated peritonitis for PD peritonitis


  • Develops in large, clinically obvious ascites secondary to cirrhosis
    • Portal hypertension → bowel edema → normal flora translocates across bowel wall into the peritoneum
  • 30% of ascitic patients will develop spontaneous bacterial peritonitis (SBP) in a given year

Causative Agents

Clinical Features

Ascites secondary to cirrhosis.

Differential Diagnosis

Diffuse Abdominal pain

Abdominal distention


Although not the diagnostic test of choice, acute abdominal CT of SBP (top images) shows ascites and thickened intestinal wall (arrowhead). Bottom images show resolution after discharge.

Consider alternative diagnoses at the same time

SBP Work-Up of Ascitic Fluid via Paracentesis

  • Cell count with differential
  • Gram stain
  • Culture (10cc in blood culture bottle)
  • Glucose
  • Protein


  • Albumin and SERUM albumin
  • LDH and SERUM LDH at same time
  • Amylase

Specific circumstances

  • TB smear and culture
  • Cytology
  • TG
  • Billirubin

Diagnosis of SBP via Ascitic Fluid Analysis

Standard Evaluation

  • Paracentesis results supporting a diagnosis of SBP:
    • Absolute neutrophil count (PMNs) ≥250, pH <7.35, OR blood-ascites pH gradient >0.1[1]
    • Bacteria on gram stain (single type)
    • SAAG > 1.1
      • Diagnostic of portal hypertension with 97% accuracy[2]
      • SBP rarely develops in patients without portal hypertension
    • Protein < 1, Glucose > 50 (otherwise concern for secondary bacterial peritonitis)

For bloody tap, subtract 1 WBC for every 250 RBC[3]

If on peritoneal dialysis

See Peritoneal dialysis-associated peritonitis

  • Cell count >100/mm with >50% neutrophils most consistent with infection[4]

Spontaneous versus secondary bacterial peritonitis

  • Importance of distinction
    • Mortality of secondary bacterial peritonitis (eg. perforated appendicitis, cholecystitis) ~100% if treatment is only antibiotics without surgery
    • Mortality of unnecessary surgery in patients with SBP ~80%
  • Laboratory findings
    • Secondary bacterial peritonitis strongly suggested by:
      • Neutrocytic fluid (PMN ≥250) with two or more of the following:
        • Total protein concentration >1 g/dL (10 g/L)
        • Glucose concentration <50 mg/dL (2.8 mmol/L)
        • LDH greater than upper limit of normal for serum
      • Ascitic alk phos >240
      • Gram stain
        • Large numbers of different bacterial forms
  • Imaging
    • If evidence of secondary bacterial peritonitis obtain abdominal imaging
      • If no evidence of free air or contrast extravasation then surgery is not indicated




Reduces renal failure and hospital mortality if given within 6 hours[6][7][8]

  • Give for all or (larger effect) if creatinine >1mg/dL, BUN >30mg/dL, or T Bili >4mg/dL
  • 1.5gm/kg at within 6 hrs of diagnosis; 1gm/kg on day 3


  • Most admitted
    • Can consider discharge with PO antibiotics if has mild, uncomplicated disease and close follow up

See Also


  1. Wilkerson R, Sinert, R. The Use of Paracentesis in the Assessment of the Patient With Ascites. Ann Emerg Med 2009, 54(3): 465-68.
  2. Runyon BA, Montano AA, Akriviadis EA, et al. The serum-ascites albumin gradient is superior to the exudate-transudate concept in the differential diagnosis of ascites. Ann Intern Med 1992; 117:215.
  3. Hoefs JC "Increase in ascites white blood cell and protein concentrations during diuresis in patients with chronic liver disease."Hepatology. 1981;1(3):249. PMID 7286905
  4. ISPD GUIDELINES/RECOMMENDATIONS http://www.ispd.org/guidelines/articles/update/ispdperitonitis.pdf
  5. Haines EJ, Oyama LC: Disorders of the Liver and Biliary Tract, in Walls RM, Hockberger RS, Gausche-Hill M, et al (eds): Rosen’s Emergency Medicine: Concepts and Clinical Practice, ed 9. Philadelphia, Elsevier 2018, (Ch) 80:p 1083-1103.
  6. Jamtgaard, et al. Does albumin infusion reduce renal impairment and mortality in patients with SBP. Annals of EM. April 2016. 67(4):458-458.
  7. Sort, P et al. Effect of intravenous albumin on renal impairment and mortality in patients with cirrhosis and spontaneous bacterial peritonitis. N Engl J Med. 1999 Aug 5;341(6):403-9.
  8. Xue, HP et al. Effect of albumin infusion on preventing the deterioration of renal function in patients with spontaneous bacterial peritonitis. Chinese Journal of Digestive Diseases, 2002 Jan 3: 32-34.