Spontaneous Bacterial Peritonitis, Emergency Medicine

Basics

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.

Diagnosis

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

Treatment

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

Follow-Up

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

Infections related to continuous abdominal peritoneal dialysis: ‚

Symptoms: Cloudy peritoneal fluid (90%), abdominal pain (80%), and fever (50%)
Signs: Abdominal tenderness 70%
Diagnosis: Peritoneal WBCs >100/mL with >50% PMNs and positive Gram stain or culture:
- Fluid should be accessed by trained personnel
Microbiology:
- >50% of cases are due to gram-positives, most commonly staphylococci
- E. coli is an uncommon cause of peritonitis in patients with chronic ambulant peritoneal dialysis
Treatment:
- Antibiotics are given through the intraperitoneal (IP) route
- 1st choice: Cefazolin (1 g IP per day) + ceftazidime (1 g IP per day)
- Vancomycin (2 g IP every week) is an alternative to cefazolin
- Amikacin 2 mg/kg/day IP

Followup Recommendations

Gastroenterology or PCP follow-up for patients with SBP ‚

Pearls and Pitfalls

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

Additional Reading

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.

Codes

ICD9

567.23 Spontaneous bacterial peritonitis ‚

ICD10

K65.2 Spontaneous bacterial peritonitis ‚

SNOMED

11836002 Primary bacterial peritonitis (disorder)

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