Overview
Peritonitis
Quick Reference
Critical Alerts
- Peritonitis is a surgical emergency: Unless SBP (medical management)
- Delay in surgery increases mortality: Source control is key
- Resuscitate while preparing for OR: Fluids, antibiotics before surgery
- SBP in cirrhotic patients: Paracentesis is diagnostic and prognostic
- Rigid abdomen = perforation until proven otherwise: Emergent imaging/surgery
- Broad-spectrum antibiotics covering GI flora: Start immediately
Key Diagnostics
| Finding | Significance |
|---|---|
| Diffuse abdominal tenderness | Generalized peritonitis |
| Guarding and rigidity | Peritoneal irritation |
| Rebound tenderness | Peritoneal inflammation |
| Free air on imaging | Perforated viscus |
| Ascitic fluid WBC >50 PMN/μL | SBP (in cirrhosis) |
Emergency Treatments
| Condition | Treatment | Details |
|---|---|---|
| Secondary peritonitis | Emergent surgery + antibiotics | Pip-tazo, ceftriaxone+metronidazole, or meropenem |
| SBP | Ceftriaxone 2g IV + albumin | No surgery needed |
| Fluid resuscitation | Crystalloids | 30 mL/kg if septic |
| Source control | Surgery | Repair perforation, drain abscess |
Definition
Overview
Peritonitis is inflammation of the peritoneum, the membrane lining the abdominal cavity. It is typically caused by infection (bacterial) and represents a medical and surgical emergency. Secondary peritonitis (from GI perforation) requires emergent surgery for source control, while spontaneous bacterial peritonitis (SBP) in patients with cirrhosis is managed medically.
Classification
By Source:
| Type | Description | Management |
|---|---|---|
| Primary (SBP) | Infection without GI perforation; occurs in ascites/cirrhosis | Medical (antibiotics + albumin) |
| Secondary | GI perforation, leak, or ischemia | Surgical (source control) |
| Tertiary | Persistent/recurrent infection after treatment of secondary | Often requires repeat surgery, broader antibiotics |
By Distribution:
| Type | Description |
|---|---|
| Localized | Contained abscess or phlegmon |
| Generalized | Diffuse peritoneal involvement |
Epidemiology
- SBP incidence in cirrhosis with ascites: 10-30% per year
- Secondary peritonitis mortality: 10-50% (depends on source, timing)
- Common sources: Perforated appendix, perforated peptic ulcer, diverticular perforation, bowel ischemia
Etiology
Secondary Peritonitis Causes:
| Source | Examples |
|---|---|
| Appendicitis | Perforated appendix |
| Peptic ulcer | Perforated duodenal or gastric ulcer |
| Diverticulitis | Perforated sigmoid diverticulum |
| Cholecystitis | Perforated gallbladder |
| Bowel ischemia | Mesenteric ischemia, volvulus |
| Trauma | Bowel perforation |
| Anastomotic leak | Post-surgical |
| Pancreatitis | Infected pancreatic necrosis |
SBP Pathogens (Cirrhosis):
| Organism | Frequency |
|---|---|
| E. coli | 40-50% |
| Klebsiella | 10-20% |
| Streptococcus (pneumoniae, viridans) | 20% |
| Enterococcus | 5% |
| Other Gram-negatives | 10% |
Pathophysiology
Secondary Peritonitis Mechanism
- Breach of GI barrier: Perforation, ischemia, leak
- Spillage of GI contents: Bacteria, bile, gastric acid, fecal matter
- Peritoneal contamination: Bacterial overgrowth
- Inflammatory response: Cytokine release, capillary leak
- Systemic sepsis: If untreated → shock, multi-organ failure
SBP Mechanism
- Bacterial translocation: From gut to mesenteric lymph nodes
- Bacteremia: Hematogenous spread
- Seeding of ascites: Impaired peritoneal defense
- Infection of ascitic fluid: Meets diagnostic criteria
Consequences
- Fluid sequestration (third-spacing)
- Sepsis and septic shock
- Multi-organ dysfunction
- Ileus
- Abscess formation
- Death if untreated
Clinical Presentation
Symptoms
Secondary Peritonitis:
SBP:
History
Key Questions:
Physical Examination
Secondary Peritonitis:
| Finding | Significance |
|---|---|
| Diffuse abdominal tenderness | Generalized peritoneal irritation |
| Guarding (voluntary → involuntary) | Peritonitis, perforation |
| Rigidity ("Board-like" abdomen) | Classic for perforation |
| Rebound tenderness | Peritoneal inflammation |
| Absent bowel sounds | Ileus |
| Fever, tachycardia | Systemic response |
| Hypotension | Septic shock |
SBP:
Severe abdominal pain
Common presentation.
Pain worsening with movement
Common presentation.
Anorexia, nausea, vomiting
Common presentation.
Fever
Common presentation.
History suggestive of underlying cause (e.g., prior ulcer, diverticulitis)
Common presentation.
Red Flags
Life-Threatening Features
| Finding | Concern | Action |
|---|---|---|
| Rigid abdomen | Perforated viscus | Emergent surgery |
| Free air on imaging | Perforation | Surgery |
| Septic shock | Severe sepsis | Resuscitation, ICU, source control |
| Worsening encephalopathy (SBP) | Severe SBP | Paracentesis, antibiotics |
| Hemodynamic instability | Sepsis | Fluids, vasopressors, source control |
| Multi-organ failure | Late presentation | ICU, aggressive management |
Differential Diagnosis
Other Causes of Acute Abdomen
| Diagnosis | Features |
|---|---|
| Pancreatitis | Epigastric pain, lipase elevated, no free air |
| Bowel obstruction | Colicky pain, distension, dilated bowel |
| Mesenteric ischemia | Severe pain out of proportion, lactic acidosis |
| Cholecystitis | RUQ pain, Murphy's sign, ultrasound findings |
| Pyelonephritis | Flank pain, CVA tenderness, pyuria |
| Ruptured AAA | Hypotension, pulsatile mass, back pain |
| Ectopic pregnancy | Reproductive age female, positive hCG |
Diagnostic Approach
Imaging
CT Abdomen/Pelvis with Contrast (Preferred):
| Finding | Interpretation |
|---|---|
| Free air | Perforation |
| Free fluid | Blood, pus, bowel contents |
| Bowel wall thickening | Inflammation, ischemia |
| Abscess | Localized infection |
| Signs of source (appendicitis, diverticulitis) | Directs surgery |
Upright or Left Lateral Decubitus X-Ray:
- Free air under diaphragm (perforation)
- Less sensitive than CT
Ultrasound:
- Assess ascites (SBP)
- RUQ for gallbladder disease
- FAST exam for free fluid
Laboratory Studies
| Test | Purpose |
|---|---|
| CBC | WBC elevation |
| BMP | Renal function, electrolytes |
| Lactate | Sepsis, ischemia |
| Lipase | Rule out pancreatitis |
| LFTs | Liver function (SBP) |
| Coagulation | Pre-operative, cirrhosis |
| Blood cultures | Bacteremia |
| Type and screen | Pre-operative |
| Urine hCG | Ectopic pregnancy (women) |
Paracentesis (For SBP)
Diagnostic Criteria for SBP:
- Ascitic fluid WBC >500/μL OR PMN >250/μL
- Positive ascitic fluid culture (often negative)
Paracentesis Findings:
| Parameter | SBP | Secondary Peritonitis |
|---|---|---|
| PMN count | >50/μL | Often >0,000/μL |
| Ascitic protein | Low (<1 g/dL usually) | Often high |
| Glucose | Normal | Low |
| LDH | Low | High (>25) |
| Culture | Monomicrobial (often negative) | Polymicrobial |
Runyon Criteria (Secondary vs SBP): ≥2 of: Glucose <50, Protein >1 g/dL, LDH > serum → Consider secondary peritonitis (surgical)
Treatment
Principles of Management
- Resuscitation: IV fluids, correct coagulopathy
- Broad-spectrum antibiotics: Cover GI flora
- Source control: Surgery for secondary peritonitis
- Supportive care: Pain management, NG tube, monitoring
Secondary Peritonitis
Antibiotics (Cover Gram-negatives, anaerobes, ± Enterococcus):
| Regimen | Agents |
|---|---|
| Single agent | Piperacillin-Tazobactam 4.5g IV q6h |
| Single agent | Meropenem 1g IV q8h |
| Combination | Ceftriaxone 2g IV + Metronidazole 500mg IV q8h |
| Combination | Ciprofloxacin + Metronidazole |
Duration: Typically 5-7 days (shorter with adequate source control)
Surgical Source Control:
- Exploratory laparotomy or laparoscopy
- Repair perforation, resect necrotic bowel
- Drain abscesses
- Peritoneal washout
- Timing: Ideally within 6-12 hours of diagnosis
Spontaneous Bacterial Peritonitis (SBP)
Antibiotics:
| Agent | Dose | Notes |
|---|---|---|
| Ceftriaxone | 2g IV q24h | First-line |
| Cefotaxime | 2g IV q8h | Alternative |
| Fluoroquinolone (levo/cipro) | If cephalosporin allergy | Watch for resistance |
Duration: 5-7 days
Albumin:
- 1.5 g/kg IV on day 1 + 1 g/kg on day 3
- Reduces renal failure and mortality in SBP
NO surgery for SBP unless concern for secondary peritonitis
Supportive Care
| Intervention | Details |
|---|---|
| IV fluids | Crystalloids; avoid over-resuscitation in cirrhosis |
| NG tube | Decompression if ileus/obstruction |
| NPO | Until source controlled |
| Pain management | Opioids PRN (after exam) |
| VTE prophylaxis | If not actively bleeding |
| ICU admission | If hemodynamically unstable |
Disposition
ICU Admission
- Septic shock
- Multi-organ dysfunction
- Post-operative monitoring
- Hemodynamic instability
Floor Admission
- Stable peritonitis awaiting or post surgery
- SBP stable on antibiotics
Surgical Consultation
- All cases of secondary peritonitis (EMERGENT)
- SBP not responding to medical therapy
- Concern for secondary peritonitis in cirrhotic
Follow-Up
| Situation | Follow-Up |
|---|---|
| SBP resolved | GI/Hepatology; consider prophylaxis |
| Post-surgical | Surgery clinic; wound care |
| Recurrent SBP | Evaluate for TIPS, transplant |
Patient Education
Condition Explanation
- "You have an infection in your abdomen that is very serious."
- "We need to give you antibiotics and may need surgery to fix the source."
- "This can progress quickly, so we need to act fast."
For SBP Patients (Cirrhosis)
- "The infection is in the fluid in your abdomen."
- "We can treat this with antibiotics and a protein infusion."
- "You may need medication to prevent this from happening again."
Special Populations
Cirrhotic Patients (SBP)
- High mortality if untreated (30-50%)
- Prophylaxis after first SBP: Norfloxacin or TMP-SMX
- Renal dysfunction common (hepatorenal syndrome)
- Avoid nephrotoxins
- May need TIPS or transplant evaluation
Immunocompromised
- Atypical organisms possible
- May have blunted clinical findings
- Low threshold for imaging and empiric therapy
Elderly
- May present atypically
- Higher mortality
- More comorbidities
Post-Operative Patients
- Consider anastomotic leak
- Low threshold for imaging
- Early surgical re-exploration if suspected
Quality Metrics
Performance Indicators
| Metric | Target | Rationale |
|---|---|---|
| Antibiotics within 60 minutes of sepsis recognition | 100% | Reduces mortality |
| Paracentesis for cirrhotic with ascites + infection concern | 100% | Diagnoses SBP |
| Surgery within 6-12 hours for secondary peritonitis | >0% | Source control |
| Blood cultures before antibiotics | >0% | Identify organism |
| Albumin given for SBP | 100% | Reduces renal failure |
Documentation Requirements
- Suspected source
- Imaging findings
- Antibiotic timing
- Surgical consultation
- Resuscitation efforts
Key Clinical Pearls
Diagnostic Pearls
- Rigid abdomen = perforation: Treat as surgical emergency
- Free air = perforation: Needs OR, not more imaging
- SBP can be subtle: Low threshold for paracentesis in cirrhosis
- PMN >250/μL = SBP: Even with negative culture
- Secondary peritonitis in cirrhosis: Consider if polymicrobial or high LDH/protein in ascites
- CT is gold standard for secondary peritonitis: Identifies source and complications
Treatment Pearls
- Source control saves lives: Surgery for secondary peritonitis
- Antibiotics cover GI flora: Gram-negatives + anaerobes
- SBP: No surgery, yes albumin: Prevents hepatorenal syndrome
- Don't delay surgery for resuscitation alone: Resuscitate en route to OR
- Meropenem or pip-tazo: Good single-agent options
- Duration 5-7 days with source control: Shorter is better if controlled
Disposition Pearls
- ICU for unstable patients: Sepsis, shock, multi-organ failure
- Surgical consult for all secondary peritonitis: Immediate
- SBP prophylaxis after first episode: Reduces recurrence
- Liver transplant evaluation for recurrent SBP: Long-term plan
References
- Sartelli M, et al. WSES guidelines for management of intra-abdominal infections. World J Emerg Surg. 2017;12:29.
- Runyon BA. Management of adult patients with ascites due to cirrhosis. Hepatology. 2013;57(4):1651-1653.
- Sort P, et al. Effect of intravenous albumin on renal impairment and mortality in patients with cirrhosis and spontaneous bacterial peritonitis. N Engl J Med. 1999;341(6):403-409.
- Mazuski JE, et al. The Surgical Infection Society Revised Guidelines on the Management of Intra-Abdominal Infection. Surg Infect. 2017;18(1):1-76.
- Rimola A, et al. Diagnosis, treatment and prophylaxis of spontaneous bacterial peritonitis. J Hepatol. 2000;32(1):142-153.
- European Association for the Study of the Liver (EASL). Clinical practice guidelines on the management of ascites, spontaneous bacterial peritonitis. J Hepatol. 2010;53(3):397-417.
- Solomkin JS, et al. Diagnosis and Management of Complicated Intra-abdominal Infection. Clin Infect Dis. 2010;50(2):133-164.
- UpToDate. Spontaneous bacterial peritonitis in adults: Treatment and prophylaxis. 2024.