A 62-year-old woman with cirrhosis and ascites develops fever, hypotension, and tachycardia. Diagnostic paracentesis shows elevated polymorphonuclear leukocytes. What is the most common site of infection in patients developing septic shock in the setting of advanced liver disease?

Explanation

## Most Common Site of Infection in Cirrhosis-Associated Septic Shock **Key Point:** Spontaneous bacterial peritonitis (SBP) is the most common bacterial infection and the leading cause of septic shock in patients with advanced cirrhosis and ascites. ### Infection Sites in Cirrhotic Patients | Site | Frequency | Pathophysiology | Organisms | |------|-----------|-----------------|----------| | **Spontaneous bacterial peritonitis** | 40–50% | Bacterial translocation; impaired opsonization | *E. coli*, *Klebsiella*, *Streptococcus* | | Pneumonia | 20–30% | Aspiration; immunosuppression | *Streptococcus pneumoniae*, *S. aureus* | | Urinary tract infection | 15–20% | Catheterization; impaired immunity | *E. coli*, *Klebsiella* | | Spontaneous bacteremia (no source) | 10–15% | Bacterial translocation | Gram-negative bacilli | **High-Yield:** SBP occurs in 10–30% of cirrhotic patients with ascites and is a major cause of mortality. It is defined by ascitic fluid PMN count ≥250 cells/mm³ (or ≥500 cells/mm³ if culture-positive) WITHOUT evidence of secondary peritonitis. ### Pathophysiology of SBP 1. **Bacterial translocation** from the gut due to: - Increased intestinal permeability - Portal hypertension and collateral circulation - Impaired gut motility 2. **Impaired opsonization** in cirrhosis: - Reduced complement levels - Decreased immunoglobulin production - Impaired reticuloendothelial function 3. **Result:** Spontaneous seeding of ascites with enteric flora **Clinical Pearl:** SBP typically presents with fever, abdominal pain, and deterioration in hepatic encephalopathy. Paracentesis is diagnostic — do not delay it while awaiting culture results. Empiric antibiotics (3rd-generation cephalosporin) should be started immediately. **Mnemonic — Risk factors for SBP: CHAPS** - **C**irrhosis with ascites - **H**ypoalbuminemia (albumin <1.5 g/dL) - **A**scitic fluid protein <1 g/dL - **P**rior SBP episode - **S**pontaneous variceal bleeding **Warning:** Do not confuse SBP (spontaneous, no perforation) with secondary peritonitis (perforation of viscus). Secondary peritonitis requires surgical intervention and has multiple organisms. [cite:Harrison 21e Ch 297; Robbins 10e Ch 18]