DESCRIPTION

• Infection of ascites fluid without an evident intra-abdominal surgically treatable source:
  • Ascites fluid polymorphonuclear leukocyte count (PMN) > 250/mL with a positive bacterial peritoneal fluid culture
• Must be distinguished from secondary bacterial peritonitis:
  • Nonsurgical management of secondary bacterial peritonitis carries 100% mortality.
  • Surgical management of spontaneous bacterial peritonitis (SBP) carries 80% mortality
• Up to 30% yearly incidence of SBP in patients with ascites

ETIOLOGY

• Mechanism:
  • Portal hypertension causes translocation of intestinal bacteria through edematous gut mucosa to the peritoneal cavity
  • Variceal bleeding increases the risk of SBP due to a compromised barrier between the GI tract and blood stream
  • Transient bacteremia with low serum complement
  • Decreased host defense mechanisms
  • Impaired activity of reticuloendothelial system phagocytosis and opsonization
  • Can also seed ascitic fluid via bacteremia from infections outside of the gut
• Usually seen in the setting of cirrhosis:
  • Rare in other conditions causing ascites (nephrotic syndrome or CHF)
• Predominant organisms:
  • 63% aerobic gram-negative (Escherichia coli, Klebsiella, others)
  • 15% gram-positive (Streptococci)
  • 6–10% enterococci
  • < 1% anaerobic
• Gram-positives account for 50% of cases in patients who are on prophylactic therapy with fluoroquinolones.

[Outline]

• DESCRIPTION
• ETIOLOGY

SIGNS AND SYMPTOMS

Up to 30% of patients with SBP have no signs or symptoms of infection.

History

• Abdominal pain: Diffuse, constant, often very mild
• Fever, chills
• Diarrhea from bacterial overgrowth
• Worsening ascites
• Altered mental status
• Fatigue, myalgias

Physical Exam

• Fever is the most common sign:
  • A lower threshold for fever (> 37.8°C or > 100°F) is maintained for cirrhotic patients owing to baseline hypothermia
  • 80% of patients with SBP have fevers and chills
• Altered mental status
• Ascites
• Abdominal tenderness:
  • Development of a rigid abdomen may not occur because of the separation of visceral and parietal pleura due to ascites

ESSENTIAL WORKUP

• Paracentesis is the mainstay of diagnosis unless patient has peritoneal dialysis
• Coagulopathy does not have to be corrected before the procedure (except for platelets < 20,000)
• Procedure:
  • Use ultrasound guidance when available
  • Location (with patient supine):
    • 3–5 cm cephalad and medial to anterosuperior iliac spine, lateral to the rectus sheath OR
    • 2 cm caudad to the umbilicus (ensure bladder emptying beforehand)
  • 40–50 mL should be aspirated, then change needles to avoid contamination:
    • 10 mL for each culture bottle
    • 10 mL for cell count, chemistries, Gram stain (lithium–heparin tube, EDTA tube, and sterile container)
  • Inoculate culture bottles with peritoneal fluid immediately at the bedside

DIAGNOSIS TESTS & INTERPRETATION

Lab

• Routine ascitic fluid assays:
  • Cell count and differential:
    • Count bands as PMNs
  • Total protein
  • Albumin
  • Culture
  • Gram stain
  • Optional fluid assays:
    • Glucose
    • LDH (from lysed PMNs)
    • Amylase
• Characteristics of ascitic fluid consistent with SBP:
  • PMNs > 250/mm³
  • Diagnosis suggested when:
    • WBC > 1,000/mm³
    • WBC > 250/mm³ with > 50% PMNs
  • Total protein < 1 g/dL
  • pH < 7.34
  • Normal amylase
  • Positive culture:
    • Only 30–50% of cultures become positive; this rate increases with high volume bedside inoculation of culture bottles
  • Positive Gram stain
  • Glucose < 50 mg/dL
  • Ascites LDH > serum LDH
  • Lactoferrin > 242 shows promise as marker for SBP
  • Serum–ascites albumin gradient > 1.1 g/dL consistent with portal hypertension
  • If hemorrhagic ascites (> 10,000 RBC/mm³), subtract 1 PMN/mm³ for every 250 RBC/mm³ in ascites fluid interpretation
• Blood tests (usually reflect underlying disease):
  • CBC with differential
  • Basic metabolic panel
  • PT/PTT
  • LFTs (including albumin)
  • Blood cultures
  • UA and culture

Imaging

• Abdominal ultrasound:
  • Confirms presence of ascites
  • Helps guide paracentesis
• Chest radiograph
• Abdominal radiographs: Flat-plate and upright to evaluate for perforation or obstruction
• Water-soluble contrast CT if suspect secondary bacterial peritonitis

Diagnostic Procedures/Surgery

Surgery consultation to consider exploratory laparotomy if free air on x-ray or extravasation of contrast on CT

DIFFERENTIAL DIAGNOSIS

• Secondary bacterial peritonitis:
  • Due to perforation or abscess
  • Polymicrobial Gram stain or 2 of the following:
    • Ascites total protein > 1 g/dL
    • Ascites glucose < 50 mg/dL
    • Ascites LDH > 1/2 upper limit of normal serum LDH or LDH> 225
  • Orange ascites with bilirubin > 6 mg/dL suggests ruptured gallbladder
• Acute hepatitis:
  • Fever, leukocytosis, abdominal pain ± ascites
  • Ascites PMNs < 250/mm³
• Culture-negative neutrocytic ascites:
  • Ascites PMNs > 250/mL, culture negative
• Monomicrobial non-neutrocytic bacterascites:
  • Due to colonization phase of SBP
  • Ascites PMNs < 250/mm³, monomicrobial culture
  • Treated like SBP if symptomatic
• Polymicrobial bacterascites:
  • Due to accidental gut perforation (1 in 1,000 paracenteses)
  • Ascites PMNs < 250/mm³, polymicrobial culture
• Pancreatitis:
  • Elevated ascites amylase
• Peritoneal carcinomatosis or tuberculous peritonitis:
  • Secondary bacterial peritonitis criteria with non-PMN predominance and lack of fever

[Outline]

• SIGNS AND SYMPTOMS
• ESSENTIAL WORKUP
• DIAGNOSIS TESTS & INTERPRETATION
• DIFFERENTIAL DIAGNOSIS

PRE-HOSPITAL

• IV fluids for hypotension
• Blood glucose for altered mental status
• Supplemental oxygen for respiratory complaints

INITIAL STABILIZATION/THERAPY

• ABCs
• Prompt antibiotic treatment and IV fluids for septic shock

ED TREATMENT/PROCEDURES

• Administer platelets before paracentesis only if platelet count is < 20,000/mm³
• Give empiric antibiotics immediately after paracentesis for:
  • Ascites PMNs > 250/mm³ or
  • Temperature > 37.8°C or
  • Altered mental status or
  • Abdominal pain/tenderness or
  • Clinical features most consistent with SBP
• Antibiotic options:
  • Ceftriaxone or cefotaxime
  • Ampicillin–sulbactam, piperacillin–tazobactam or aztreonam
  • Avoid aminoglycosides, fluoroquinolones
  • Add metronidazole for secondary bacterial peritonitis
• IV albumin is helpful in preventing renal impairment and reducing mortality in diagnosed SBP

Prognosis

• In-hospital noninfection–related mortality is 20%
• Can be precursor to hepatorenal syndrome
• 1- and 6-mo mortality rates after an episode of SBP are 32% and 69%, respectively

MEDICATION

First Line

• Cefotaxime: 2 g IV q8h
• Albumin for high-risk patients: 1.5 g/kg IV on day 1 and 1 g/kg IV on day 3

Second Line

• Ceftriaxone: 2 g IV q8h
• Piperacillin–tazobactam: 3.375 g IV q6h
• Ampicillin–sulbactam: 1.5–3 g IM/IV q6h
• Aztreonam: 0.5–2 g IM/IV q6–12h

[Outline]

• PRE-HOSPITAL
• INITIAL STABILIZATION/THERAPY
• ED TREATMENT/PROCEDURES
• Prognosis
• MEDICATION

DISPOSITION

Admission Criteria

• Admit all patients for IV antibiotics and gastroenterology consultation
• ICU admission for septic shock or severe hepatic encephalopathy

Discharge Criteria

• All patients with suspected or known SBP should be admitted.
• If patient refuses admission and has no signs of shock, encephalopathy, azotemia, or GI bleeding, a dose of IV ceftriaxone and a course of oral fluoroquinolones followed by close follow-up may be considered

Issues for Referral

• Hepatology and gastroenterology referral may be indicated
• Prophylaxis with norfloxacin or trimethoprim/sulfamethoxazole

ALERT

FOLLOW-UP RECOMMENDATIONS

Gastroenterology or PCP follow-up for patients with SBP

[Outline]

• DISPOSITION
• FOLLOW-UP RECOMMENDATIONS

• Rule out secondary bacterial peritonitis first
• Bedside inoculation of blood culture bottles with ascitic fluid increases culture yield
• Maintain high suspicion for SBP, since many patients are asymptomatic

ICD9

567.23 Spontaneous bacterial peritonitis

ICD10

K65.2 Spontaneous bacterial peritonitis

[Outline]

• ICD9
• ICD10

• Grabau CM, Crago SF, Hoff LK, et al. Performance standards for therapeutic abdominal paracentesis. Hepatology. 2004;40:484–488.
• Greenberger NJ, Blumberg RS, Burakoff R. Current Diagnosis & Treatment: Gastroenterology, Hepatology, & Endoscopy. 2nd ed. McGraw-Hill; 2012.
• Such J, Runyon BA. Spontaneous bacterial peritonitis. Clin Infect Dis. 1998;27:669–674.
• Wiest R, Krag A, Gerbes A. Spontaneous bacterial peritonitis: Recent guidelines and beyond. Gut. 2012;61(2):297–310.
• Wong CL, Holroyd-Leduc J, Thorpe KE, et al. Does this patient have bacterial peritonitis or portal hypertension? How do I perform a paracentesis and analyze the results? JAMA. 2008;299:1166–1178.

See Also (Topic, Algorithm, Electronic Media Element)

• Ascites
• GI Bleeding
• Hepatitis
• Hepatorenal Syndrome
• Abdominal Pain

We wish to acknowledge the previous authors of this chapter for their contributions on this topic: Michael Schmidt, Amer Aldeen, and Lucas Roseire.

Alison Foster-Goldman

Christopher T. Richards