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Spontaneous Bacterial Peritonitis (SBP)

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Spontaneous Bacterial Peritonitis (SBP)

Spontaneous Bacterial Peritonitis (SBP) is an acute bacterial infection of ascitic fluid without an evident surgically treatable intra-abdominal source. It occurs most commonly in patients with decompensated liver cirrhosis and ascites and is a medical emergency requiring prompt antibiotic treatment

Also called

Primary Bacterial Peritonitis

ICD-10

K65.2

Specialty

Gastroenterology

Onset

Acute

Reviewed

July 2026

On This Page

Overview

Spontaneous Bacterial Peritonitis (SBP) develops when bacteria translocate from the intestine into ascitic fluid in patients with cirrhosis and portal hypertension. The infection occurs without gastrointestinal perforation or another intra-abdominal source. Early recognition is essential because SBP can rapidly progress to sepsis, renal failure, and death if left untreated.

Etiology & Risk Factors

Etiology

Spontaneous Bacterial Peritonitis (SBP) results from bacterial translocation from the intestinal lumen into ascitic fluid without an intra-abdominal perforation.

Common Causative Organisms

  • Escherichia coli (most common)

  • Klebsiella pneumoniae

  • Streptococcus species

  • Enterococcus species

Risk Factors

  • Liver cirrhosis

  • Ascites

  • Low ascitic protein (<1.5 g/dL)

  • Previous SBP

  • Gastrointestinal bleeding

  • Advanced liver disease (Child-Pugh C)

  • Renal dysfunction

  • Proton pump inhibitor use

  • Hospitalization

Pathophysiology

Liver cirrhosis → portal hypertension and ascites → increased intestinal permeability and bacterial overgrowth → bacterial translocation across the intestinal wall → bacteria enter mesenteric lymph nodes and bloodstream → bacteria seed the ascitic fluid → impaired immune defenses in ascitic fluid allow bacterial proliferation → spontaneous infection of ascitic fluid → systemic inflammatory response, sepsis, and possible hepatorenal syndrome.

Clinical Presentation

Symptoms

  • Fever

  • Abdominal pain or tenderness

  • Increasing abdominal distension

  • Nausea and vomiting

  • Altered mental status

  • Fatigue

  • Reduced appetite

Signs

  • Diffuse abdominal tenderness

  • Ascites

  • Fever

  • Hypotension

  • Tachycardia

  • Hepatic encephalopathy

  • Signs of sepsis in severe cases

History Taking

-Ask about:

  • Fever or chills
  • Abdominal pain
  • Increasing abdominal distension
  • Nausea or vomiting
  • Confusion or drowsiness
  • Recent gastrointestinal bleeding
  • Previous SBP
  • History of cirrhosis
  • Alcohol use
  • Viral hepatitis
  • Current medications
  • Previous antibiotic prophylaxis

Physical Examination

General Examination

Assess for:

  • Fever

  • Tachycardia

  • Hypotension

  • Altered mental status

  • Signs of sepsis

Abdominal Examination

Look for:

  • Ascites

  • Diffuse abdominal tenderness

  • Rebound tenderness (may be absent)

  • Abdominal distension

  • Reduced bowel sounds

Examine for signs of chronic liver disease:

  • Jaundice

  • Spider angiomas

  • Palmar erythema

  • Muscle wasting

  • Peripheral edema

  • Asterixis

Investigations

Diagnostic Paracentesis (Gold Standard)

Perform immediately in every patient with cirrhosis and ascites who is admitted to hospital or suspected of having SBP.

Ascitic fluid analysis:

  • Cell count and differential

  • PMN count

  • Gram stain (low sensitivity)

  • Ascitic fluid culture (inoculate into blood culture bottles at bedside)

  • Protein and albumin

  • Glucose and LDH if secondary peritonitis is suspected

Diagnostic Criterion

  • PMN count ≥250 cells/mm³ confirms SBP, regardless of culture results.

Blood Tests

  • Complete blood count

  • CRP

  • Liver function tests

  • Renal function and electrolytes

  • Coagulation profile (INR/PT)

  • Serum albumin

  • Blood cultures (before antibiotics if possible)

Imaging

Not required for diagnosis but may include:

  • Abdominal ultrasound (confirm ascites)

  • CT abdomen if secondary peritonitis or perforation is suspected

Diagnosis

-Diagnosis is based on:

  • Cirrhosis with ascites
  • Diagnostic paracentesis
  • Ascitic fluid PMN count ≥250 cells/mm³
  • Positive ascitic culture (supports diagnosis but is not required)
  • Exclusion of a surgically treatable intra-abdominal source
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Related Topics

Management

Management

-Initial Management

  • Hospital admission

  • Immediate diagnostic paracentesis

  • Start empirical IV antibiotics promptly

  • Supportive care

  • Monitor vital signs and urine output

-Antibiotic Therapy

First-line:

  • Third-generation cephalosporin

    • Cefotaxime

    • Ceftriaxone

-Alternative therapy:

  • Broad-spectrum antibiotics according to local resistance patterns for healthcare-associated infection or resistant organisms

-Albumin Therapy

Give intravenous albumin to reduce the risk of hepatorenal syndrome, especially in patients with renal dysfunction or severe disease.

-Supportive Care

  • Intravenous fluids if indicated

  • Correct electrolyte abnormalities

  • Treat hepatic encephalopathy

  • Manage acute kidney injury

  • Treat sepsis if present

Secondary Prophylaxis

After recovery:

  • Long-term oral antibiotic prophylaxis (e.g., norfloxacin or ciprofloxacin where appropriate according to local guidelines)

  • Optimize management of cirrhosis

  • Assess for liver transplantation in suitable patients

Complications

  • Sepsis
  • Septic shock
  • Hepatorenal syndrome
  • Acute kidney injury
  • Hepatic encephalopathy
  • Recurrent SBP
  • Multi-organ failure
  • Death

Prognosis

Spontaneous Bacterial Peritonitis (SBP) is associated with high morbidity and mortality if untreated. Early diagnosis and prompt treatment with antibiotics and albumin significantly improve survival. Despite successful treatment, recurrence is common, and many patients should be evaluated for liver transplantation.

 

Key Points / Clinical Pearls

  • Spontaneous Bacterial Peritonitis (SBP) is an infection of ascitic fluid without an intra-abdominal perforation.
  • It occurs mainly in patients with cirrhosis and ascites.
  • Escherichia coli is the most common causative organism.
  • Diagnostic paracentesis is the gold standard investigation.
  • Ascitic fluid PMN ≥250 cells/mm³ is diagnostic.
  • Do not delay antibiotic therapy after paracentesis.
  • Third-generation cephalosporins are first-line treatment.
  • Intravenous albumin reduces the risk of hepatorenal syndrome and mortality.
  • Long-term antibiotic prophylaxis is recommended after an episode of SBP.
  • Recurrent SBP indicates advanced liver disease and should prompt consideration of liver transplantation
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