Spontaneous Bacterial Peritonitis (SBP) in Cirrhosis
What is SBP?
SBP is a bacterial infection of ascitic fluid in cirrhotic patients without any surgically treatable intra-abdominal source, diagnosed when ascitic fluid neutrophil count exceeds 250 cells/mm³. 1 This is a life-threatening complication occurring in decompensated cirrhosis with approximately 20% in-hospital mortality despite appropriate treatment. 1
The infection is typically monobacterial, with approximately 60% caused by gram-negative bacteria (most commonly E. coli, followed by Klebsiella pneumoniae), though there has been a concerning shift toward gram-positive organisms and multidrug-resistant organisms (MDROs), particularly in nosocomial infections where MDROs now represent 35% of cases. 1
Workup and Diagnosis
When to Perform Diagnostic Paracentesis
Every cirrhotic patient with ascites admitted emergently to the hospital must undergo diagnostic paracentesis immediately, even without symptoms of infection. 1 This is critical because up to one-third of SBP patients are completely asymptomatic or present only with encephalopathy or acute kidney injury. 1
Additional indications for paracentesis include: 1
- Any signs/symptoms suggestive of infection (fever, hypothermia, chills, abdominal pain/tenderness)
- Clinical deterioration (worsening encephalopathy, acute kidney injury, jaundice)
- Tense ascites with acute kidney injury
Diagnostic Criteria
The diagnosis is established by ascitic fluid absolute neutrophil count >250/mm³. 1 This cutoff has the highest sensitivity and was chosen to avoid missing treatable cases. 1
Essential Laboratory Steps
Obtain ascitic fluid culture by inoculating at least 10 mL of ascitic fluid into blood culture bottles at the bedside before any antibiotics are given. 1 This increases culture sensitivity to >90%. 1
Simultaneously obtain: 1
- Blood cultures (increases organism isolation rates)
- Complete blood count with differential
- Urine culture
- Chest x-ray
- Skin examination for cellulitis
A critical pitfall: Culture results are frequently negative (even with proper technique), but culture positivity is not required for diagnosis—the neutrophil count >250/mm³ is diagnostic. 1 However, cultures are essential to guide antibiotic therapy and assess susceptibility. 1
Treatment
Empirical Antibiotic Therapy
Start empirical antibiotics immediately upon diagnosis (neutrophil count >250/mm³) without waiting for culture results—every hour of delay in septic shock increases mortality by 10%. 1, 2
Community-Acquired SBP (First-Line)
Third-generation cephalosporins are first-line therapy for community-acquired SBP: 1, 2
- Cefotaxime 2g IV every 8-12 hours for 5-7 days (4g/day is as effective as 8g/day) 1, 2
- Ceftriaxone 1-2g IV every 12-24 hours is an equally effective alternative 2
These achieve infection resolution rates of 77-98%. 1, 2
Alternative Options for Community-Acquired SBP
- Amoxicillin/clavulanic acid (1g/0.2g IV every 8 hours, then switch to 0.5g/0.125g PO every 8 hours) achieves 87% resolution rate, similar to cefotaxime 1, 2
- Oral ofloxacin (400mg PO every 12 hours) for uncomplicated SBP only (no renal failure, hepatic encephalopathy, GI bleeding, ileus, or shock) achieves 84% resolution 1, 2
Do NOT use quinolones if: 1, 2
- Patient is already on quinolone prophylaxis
- High local prevalence of quinolone-resistant bacteria
- Nosocomial SBP
Never use aminoglycosides (e.g., tobramycin) due to nephrotoxicity. 1, 2
Nosocomial or Healthcare-Associated SBP
For nosocomial SBP, recent hospitalization, or critically ill ICU patients, use broader-spectrum coverage due to high MDRO prevalence (35%): 1, 2
- Meropenem 1g IV every 8 hours PLUS daptomycin 6mg/kg/day 2
- Alternative: Piperacillin/tazobactam in areas with low MDRO prevalence 3
The shift toward MDROs has decreased response rates to traditional cephalosporins in these settings. 1
Essential Adjunctive Therapy: Intravenous Albumin
Add IV albumin to antibiotic therapy in all SBP patients with baseline bilirubin ≥4 mg/dL (68 μmol/L) OR creatinine ≥1 mg/dL (88 μmol/L): 1, 2
- 1.5 g/kg body weight at diagnosis
- 1.0 g/kg on day 3
This reduces hepatorenal syndrome from 30% to 10% and mortality from 29% to 10%. 1, 2 Albumin improves circulatory function while crystalloids and hydroxyethyl starch do not provide this benefit. 1
For patients with bilirubin <4 mg/dL and creatinine <1 mg/dL, the benefit is less clear as hepatorenal syndrome incidence is very low (0-7%) in this group. 1
Monitoring Treatment Response
Perform repeat paracentesis at 48 hours to assess neutrophil count. 1, 2
Treatment failure is suspected if: 1, 2
- Ascitic neutrophil count fails to decrease to <25% of pre-treatment value
- Worsening clinical signs/symptoms
- No marked reduction or increase in neutrophil count
Resolution is confirmed by: 1
- Ascitic neutrophil count <250/mm³
- Sterile cultures (if initially positive)
If treatment fails, consider: 1
- Resistant bacteria (change antibiotics based on susceptibility or use broader empiric coverage)
- Secondary bacterial peritonitis (requires CT imaging and surgical consultation) 1
Prevention After SBP Episode
All patients surviving an SBP episode require indefinite long-term antibiotic prophylaxis until liver transplantation or death. 2, 4 Without prophylaxis, SBP recurrence rate is 68-70% within one year. 2, 4
Norfloxacin 400mg PO daily is the most studied regimen, reducing recurrence from 68% to 20%. 2, 4 Local resistance patterns should guide prophylaxis choice. 2
Key Clinical Pitfalls to Avoid
- Never delay antibiotics waiting for culture results—start immediately upon diagnosis 1, 2
- Never skip diagnostic paracentesis in hospitalized cirrhotic patients with ascites, even without symptoms 1
- Never use aminoglycosides due to nephrotoxicity 1, 2
- Recognize nosocomial vs. community-acquired SBP—nosocomial requires broader coverage due to 35% MDRO rate 1, 2
- Don't forget albumin in patients with elevated bilirubin or creatinine—it significantly reduces mortality 1, 2
- Inoculate blood culture bottles at bedside before antibiotics to maximize culture yield 1
- Consider secondary peritonitis if treatment fails—requires CT imaging and surgical evaluation 1