## Diagnosis and Management: Spontaneous Bacterial Peritonitis (SBP) ### Diagnostic Criteria Met **High-Yield:** This patient fulfills diagnostic criteria for spontaneous bacterial peritonitis (SBP): - Ascitic fluid PMN count ≥250 cells/μL (here: 350 with 85% neutrophils) - Clinical signs of peritonitis (fever, abdominal pain) - High SAAG (1.8 g/dL) confirming portal hypertension - Negative culture (culture is often negative in SBP; diagnosis is clinical + cell count) **Key Point:** SBP is a life-threatening complication of decompensated cirrhosis with high mortality if untreated. Do NOT wait for culture results to initiate therapy. ### Why This Is SBP, Not Secondary Peritonitis | Feature | SBP | Secondary Peritonitis | |---------|-----|----------------------| | **Ascitic protein** | Usually < 1 g/dL | Often > 1 g/dL | | **Ascitic glucose** | Often < 50 mg/dL | Variable | | **LDH** | Low (< 225 IU/L) | Elevated | | **PMN count** | 250–2000 cells/μL | Often > 1000 | | **Multiple organisms** | Rare | Common | | **Perforation history** | None | Often present | **Clinical Pearl:** The low glucose (45 mg/dL) and low LDH (90 IU/L) with negative culture are classic for SBP, not secondary peritonitis (which would show elevated LDH and often multiple organisms). ### Optimal Management Algorithm ```mermaid flowchart TD A[Ascitic Fluid PMN ≥ 250 cells/μL + Clinical Signs]:::outcome --> B[Diagnosis: SBP]:::outcome B --> C[Start Empiric Antibiotics IMMEDIATELY]:::urgent C --> D[Third-generation Cephalosporin<br/>e.g., Cefotaxime 2g IV Q4-6H]:::action D --> E[Add Albumin Infusion]:::action E --> F[1.5 g/kg on Day 1<br/>1 g/kg on Day 3]:::action G[Monitor Renal Function]:::decision G -->|Creatinine rising| H[Add Vasoconstrictor<br/>Terlipressin or Noradrenaline]:::action G -->|Stable| I[Continue Antibiotics + Albumin]:::action H --> J[Repeat Paracentesis at 48h<br/>if no improvement]:::action I --> J J --> K[Assess Response:<br/>PMN count should decrease]:::decision K -->|Good response| L[Continue 5-7 days total]:::action K -->|No improvement| M[Consider Secondary Peritonitis<br/>or Imaging]:::urgent ``` ### Antibiotic Regimen **Key Point:** Empiric therapy for SBP: - **First-line:** Cefotaxime 2 g IV Q4–6H (or ceftriaxone 1 g IV Q12H) - **Duration:** 5–7 days - **Rationale:** Covers gram-negative organisms (E. coli, Klebsiella) and gram-positive cocci - **Allergy alternative:** Fluoroquinolone (e.g., levofloxacin) if beta-lactam allergy ### Albumin Infusion: Why It Matters **High-Yield:** Albumin infusion reduces renal failure and mortality in SBP: - **Mechanism:** Expands effective arterial blood volume, prevents HRS - **Dosing:** 1.5 g/kg on Day 1, then 1 g/kg on Day 3 - **Evidence:** Landmark RCT showed mortality reduction from 29% to 10% with albumin + antibiotics vs. antibiotics alone **Clinical Pearl:** Vasoconstrictor (terlipressin or noradrenaline) should be added if renal function deteriorates (creatinine > 1.5 mg/dL or rising), as this indicates early hepatorenal syndrome. ### Why Observation Alone Is Wrong **Warning:** Delaying antibiotics in SBP is dangerous — mortality increases significantly without prompt treatment. Culture negativity does NOT exclude SBP; diagnosis is based on ascitic PMN count and clinical presentation. [cite:Harrison 21e Ch 297; Robbins 10e Ch 18]
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