Spontaneous Bacterial Peritonitis (SBP)

A 55 year old male with a history of cirrhosis and ascites due to chronic alcohol use presents to the emergency department with diffuse abdominal pain, vomiting, and low-grade fever for two days. He also reports fatigue and increasing confusion. On examination, blood pressure is 100/60 mm Hg, pulse rate is 108 beats per minute, respiratory rate is 18 breaths per minute, and temperature is 100.2°F. The abdomen is distended with shifting dullness, with diffuse tenderness and hypoactive bowel sounds. Laboratory findings show WBC count 14,000/mm³, serum creatinine 1.8 mg/dL, and serum albumin 2.1 g/dL. Paracentesis reveals ascitic fluid neutrophil count of 380 cells/mm³. Diagnosis?

Diagnosis is Spontaneous Bacterial Peritonitis (SBP).

1. Definition

Spontaneous bacterial peritonitis is an infection of ascitic fluid without an identifiable surgically treatable intra-abdominal source.

2. Etiology

1. Escherichia coli most common
2. Klebsiella species
3. Streptococcus species

3. Pathophysiology

1. Bacterial translocation from the gut
2. Impaired host immunity in cirrhosis
3. Infection of low-protein ascitic fluid

4. Clinical Features

1. Fever
2. Diffuse abdominal pain
3. Altered mental status
4. Hypotension and tachycardia
5. May present with subtle symptoms or clinical deterioration

5. Diagnostic Evaluation

5.1 Ascitic Fluid Analysis

1. Neutrophil count ≥ 250 cells/mm³ is diagnostic
2. Ascitic fluid culture should be obtained

5.2 Laboratory Findings

1. Leukocytosis
2. Elevated creatinine indicating renal dysfunction
3. Low serum albumin

6. Key Diagnostic Insight

Cirrhosis + ascites + neutrophils ≥ 250 cells/mm³ = SBP

7. Complications

1. Hepatorenal syndrome
2. Sepsis
3. Hepatic encephalopathy
4. High mortality if untreated

8. Management

8.1 Antibiotic Therapy

1. Start empiric third-generation cephalosporin such as cefotaxime or ceftriaxone immediately

8.2 Albumin Infusion

1. Intravenous albumin reduces risk of renal failure and mortality
2. Typical dosing: 1.5 g/kg on day 1 and 1 g/kg on day 3

8.3 Secondary Prophylaxis

1. Ciprofloxacin or trimethoprim sulfamethoxazole
2. Indicated in patients with prior SBP or low ascitic protein

9. Key Clinical Insight

SBP should be suspected in any patient with cirrhosis and ascites who develops clinical deterioration, even with minimal abdominal findings

10. Exam Level Pearls

1. Ascitic neutrophils ≥ 250 cells/mm³ is diagnostic
2. E. coli is the most common organism
3. Do not delay antibiotics while awaiting culture results
4. Albumin prevents hepatorenal syndrome
5. Always perform diagnostic paracentesis in cirrhotic patients with ascites and new symptoms