Peritonitis
Definition
Peritonitis is inflammation of the peritoneum caused by infection, chemical irritation, ischemia, foreign material, or sterile inflammatory processes.
Anatomy Relevant to Peritonitis
The peritoneum is a serous membrane consisting of:
|
Layer |
Description |
|
Parietal peritoneum |
Lines abdominal wall |
|
Visceral peritoneum |
Covers abdominal organs |
The peritoneal cavity normally contains:<50–100 mL sterile fluid
Classification of Peritonitis
1. Primary (Spontaneous) Peritonitis
Infection without intra-abdominal source.occure due to translocation of bacteria
Usually monomicrobial.
|
Organism |
Frequency |
|
Escherichia coli |
Most common |
|
Klebsiella spp. |
Common |
|
Streptococcus spp. |
Common |
|
Enterococcus spp. |
Less common |
2. Secondary Peritonitis
Most common form.Usually polymicrobial.
Results from perforation or disruption of GI tract.
Examples:
- Perforated peptic ulcer
- Appendicular perforation,Perforated diverticulitis
- Bowel ischemia
- Anastomotic leak,Trauma
Runyon’s Criteria for Secondary Peritonitis
Suggests perforated viscus rather than SBP.
Present if ≥2:
|
Parameter |
Value |
|
Ascitic protein |
>1 g/dL |
|
Glucose |
<50 mg/dL |
|
LDH |
Above serum upper limit |
Sensitivity approximately 67%.
3. Tertiary Peritonitis
Persistent or recurrent intra-abdominal infection despite adequate treatment of secondary peritonitis.
Occurs in:
- ICU patients
- Immunocompromised patients
- Severe septic shock
Common pathogens:
- Enterococcus
- Candida
- Coagulase-negative staphylococci
- MDR gram negatives
4. Chemical Peritonitis
Due to sterile irritants.
Examples:
- Gastric acid leakage
- Bile
- Pancreatic enzymes
- Blood
- Urine
- Barium
Can later become infected.
Clinical Features
Pain
Initially localized
Then generalized.
Characteristics:
- Sudden onset
- Severe
- Continuous
Gastrointestinal Symptoms
- Nausea
- Vomiting
- Abdominal distension
- Constipation
- Obstipation
Systemic Symptoms
- Fever
- Chills
- Malaise
Abdominal Findings
- Guarding(Voluntary muscle contraction.)
- Rigidity(Involuntary board-like abdomen.)
- Rebound Tenderness(Pain on release of pressure.)
- Silent Abdomen(Absent bowel sounds due to paralytic ileus.)
Investigations
Laboratory Tests
|
Investigation |
Typical Findings |
Clinical Significance |
|
Complete Blood Count (CBC) |
• Leukocytosis • Neutrophilia • Leukopenia may occur in severe sepsis/septic shock |
Indicates systemic inflammatory response and infection. Leukopenia is a poor prognostic sign and may suggest overwhelming sepsis. |
|
C-Reactive Protein (CRP) |
Elevated |
Marker of inflammation; useful for diagnosis and monitoring treatment response. |
|
Procalcitonin (PCT) |
Often elevated |
More specific for bacterial infection. Useful for assessing sepsis severity, monitoring response to therapy, and guiding antibiotic stewardship. |
|
Serum Lactate |
Elevated lactate levels |
Indicates tissue hypoperfusion and occult shock. Elevated levels are associated with increased mortality. Target after resuscitation: <2 mmol/L. |
|
Renal Function Tests (RFTs) |
• Elevated serum creatinine • Elevated BUN • Electrolyte abnormalities |
May reveal acute kidney injury (AKI) due to sepsis, hypovolemia, or multiorgan dysfunction. |
|
Arterial Blood Gas (ABG) |
• Metabolic acidosis • Elevated lactate • Possible respiratory compensation |
Reflects severity of sepsis and tissue hypoxia; helps assess acid-base status and adequacy of resuscitation. |
Imaging Studies in Peritonitis
|
Imaging Modality |
Typical Findings |
Clinical Significance |
|
Upright Chest X-Ray |
• Pneumoperitoneum (free air under diaphragm) |
Classical sign of hollow viscus perforation, especially peptic ulcer perforation. Quick and widely available screening test. |
|
Abdominal X-Ray |
• Dilated bowel loops • Air-fluid levels • Free intraperitoneal air |
May suggest bowel obstruction, ileus, perforation, or advanced intra-abdominal pathology. |
|
Ultrasound (USG Abdomen) |
• Free intraperitoneal fluid • Intra-abdominal abscess • Gallbladder pathology (cholecystitis, perforation) • Localized collections |
Useful bedside investigation, especially in unstable patients. Helps guide drainage procedures and identify biliary causes. |
|
CT Abdomen with IV Contrast (Investigation of Choice) |
• Free air • Free fluid • Abscess formation • Bowel wall thickening • Extraluminal contrast leak • Ischemic bowel changes |
Most sensitive and specific investigation for diagnosing peritonitis, identifying the source, extent of contamination, and planning source control. |
Diagnostic Peritoneal Fluid Analysis
|
Indication |
Reason |
|
New-onset ascites |
Determine etiology (portal hypertension vs non-portal hypertension) |
|
Suspected Spontaneous Bacterial Peritonitis (SBP) |
Ascitic fluid PMN count, culture, and sensitivity |
|
Hospital admission in a patient with cirrhosis and ascites |
Recommended regardless of symptoms to exclude SBP |
Spontaneous Bacterial Peritonitis
Diagnostic criteria:-Ascitic PMN Count ≥250 cells/mm³
Diagnostic even if culture negative.
Monomicrobial Non-Neutrocytic Bacterascites (MNB)
Definition
|
Criterion |
Requirement |
|
Ascitic fluid culture |
Positive (single organism) |
|
Ascitic fluid PMN count |
<250 cells/mm³ |
|
Surgical source of infection |
Absent |
How Does It Occur?
Possible explanations:
- Early stage of SBP before neutrophil recruitment
- Transient bacterial translocation from the gut
- Contamination during sampling (less common if proper technique used)
- Partial treatment with antibiotics before paracentesis
Culture
Inoculate directly into:
- Aerobic blood culture bottle
- Anaerobic blood culture bottle
Improves yield.
Management
|
Community-Acquired SBP |
||
|
Drug/Regimen |
Dose |
Preferred Clinical Situations |
|
Cefotaxime(Traditional Gold Standard) |
2 g IV every 8 hours |
First-line for community-acquired SBP; most extensively studied regimen; excellent ascitic fluid penetration; preferred when local resistance rates are low. |
|
Ceftriaxone |
1 g IV daily (mild-moderate infection) 2 g IV daily (severe infection) |
Most commonly used alternative to cefotaxime due to convenient once-daily dosing; suitable for most community-acquired SBP cases. |
|
Amoxicillin-Clavulanate |
1.2 g IV every 8 hours |
Alternative option in stable patients with community-acquired SBP when third-generation cephalosporins cannot be used. |
|
Cefoperazone-Sulbactam |
3 g IV every 12 hours |
Alternative regimen in areas with favorable susceptibility patterns; useful when broader Gram-negative coverage is desired. |
|
Nosocomial / Healthcare-Associated SBP Increasing prevalence of:
|
||
|
Piperacillin-Tazobactam |
4.5 g IV every 6 hours |
Preferred for healthcare-associated SBP, recent hospitalization, recent antibiotic exposure, concern for Pseudomonas, or higher risk of resistant organisms.Non-shock patients |
|
Meropenem |
1 g IV every 8 hours |
Preferred in septic shock, known or suspected ESBL-producing organisms, prior cephalosporin exposure, recurrent SBP, or high MDR prevalence settings. |
|
Meropenem + Vancomycin |
Meropenem 1 g IV q8h+ Vancomycin (weight-based dosing) |
Severe nosocomial SBP with risk factors for both ESBL Gram-negatives and MRSA. |
|
Meropenem + Linezolid |
Meropenem 1 g IV q8h+ Linezolid 600 mg IV/PO q12h |
Consider if MRSA/VRE risk exists and renal dysfunction makes vancomycin less desirable. |
Duration of Therapy
Current Guideline Recommendation
5–7 days
If clinical improvement occurs.
Longer therapy generally unnecessary.
Albumin Therapy -Why Albumin?
SBP causes:
- Systemic vasodilation
- Effective hypovolemia
- Renal hypoperfusion
- Hepatorenal syndrome
Albumin reduces:
- Renal failure
- Need for dialysis
- Mortality
Albumin Regimen(20–25% albumin is preferred in SBP.)
Day 1-1.5 g/kg IV
Day 3-1 g/kg IV
There is no SBP-specific infusion rate mandated by guidelines. Albumin is generally infused slowly while monitoring for volume overload.2–6 hours depending on dose and comorbidities
Who Must Receive Albumin?
Current guidelines strongly recommend albumin in:
|
Criterion |
Value |
|
Creatinine |
>1 mg/dL |
|
BUN |
>30 mg/dL |
|
Bilirubin |
>4 mg/dL |
Many centers now give albumin to nearly all hospitalized SBP patients.
Monitoring Response
Repeat Diagnostic Paracentesis Recommended at 48 Hours
Particularly if:
- Severe infection
- Septic shock
- Poor clinical response
Expected Response-PMN Count Should Fall By ≥25% after 48 hours.
Oral Step-Down Therapy
After clinical improvement.
Options:
|
Drug |
Dose |
|
Ciprofloxacin |
500 mg PO BID |
|
Levofloxacin |
500–750 mg daily |
|
Amoxicillin-Clavulanate |
Selected patients |
Secondary Prophylaxis
Without prophylaxis: Recurrence rate ≈70% within 1 year
Indications-All patients who survive SBP.
|
Drug |
Dose |
When to Prefer / Comments |
|
Ciprofloxacin |
500 mg PO once daily |
Most widely used current regimen. Preferred for long-term secondary prophylaxis after recovery from SBP. Convenient once-daily dosing and widely available. |
|
Norfloxacin |
400 mg PO once daily |
Historically the standard prophylactic agent with extensive supporting evidence. Availability is limited in many countries, including some regions of India. |
|
Trimethoprim-Sulfamethoxazole |
1 Double-Strength (DS) tablet PO once daily (160 mg TMP + 800 mg SMX) |
Alternative when fluoroquinolones cannot be used due to allergy, intolerance, resistance concerns, or drug interactions. May also be considered in regions with high fluoroquinolone resistance. |
Primary Prophylaxis
Not all cirrhotic patients require prophylaxis.
Indications
Low Ascitic Protein (<1.5 g/dL)
Plus one of:
Renal Dysfunction
- Creatinine ≥1.2 mg/dL
- BUN ≥25 mg/dL
- Sodium ≤130 mEq/L
OR
Advanced Liver Failure
- Child-Pugh ≥9
- Bilirubin ≥3 mg/dL
GI Bleeding Prophylaxis
Acute upper GI bleeding in cirrhosis carries a very high risk of SBP.
Ceftriaxone-1 g IV daily for 7 days
This is guideline-mandated prophylaxis.
Secondary Peritonitis Management
Community-Acquired Mild–Moderate Secondary Peritonitis
|
Regimen |
Dose |
|
Ceftriaxone + Metronidazole |
Ceftriaxone 2 g IV daily + Metronidazole 500 mg IV q8h |
|
Cefotaxime + Metronidazole |
Cefotaxime 2 g IV q8h + Metronidazole 500 mg IV q8h |
Single-Agent Options
|
Drug |
Dose |
|
Piperacillin-Tazobactam |
4.5 g IV q6h |
Excellent coverage:
- Gram positives
- Gram negatives
- Anaerobes
High-Risk Community-Acquired Infection
High-risk factors:
- Septic shock
- Delayed presentation
- APACHE II >15
- Elderly
- Immunosuppression
Preferred:
|
Drug |
Dose |
|
Piperacillin-Tazobactam |
4.5 g IV q6h |
|
Meropenem |
1 g IV q8h |
Healthcare-Associated Peritonitis
Risk factors:
- Recent hospitalization
- Prior antibiotics
- ICU stay
- MDR colonization
Preferred:
|
Drug |
Dose |
|
Meropenem |
1 g IV q8h |
|
Imipenem-Cilastatin |
500 mg IV q6h |
MRSA Coverage
Add if:
- Known MRSA colonization
- Prior MRSA infection
- Healthcare-associated infection
|
Drug |
Dose |
|
Vancomycin |
Weight-based |
|
Linezolid |
600 mg q12h |
Enterococcal Coverage
Not routinely required in all patients.
Consider in:
- Healthcare-associated infection
- Immunocompromised patients
- Postoperative infection
- Liver transplant recipients
Options:
- Ampicillin
- Piperacillin-Tazobactam
- Vancomycin
Antifungal Therapy
Not Recommended Routinely
Do NOT add empirically for all patients.
Indications
|
Condition |
|
Recurrent GI perforation |
|
Upper GI perforation |
|
Esophageal perforation |
|
TPN use |
|
Immunosuppression |
|
Candida isolated from peritoneal cultures |
|
Septic shock with high Candida risk |
Preferred Agents
|
Drug |
Dose |
|
Fluconazole |
800 mg loading then 400 mg/day |
|
Micafungin |
100 mg/day |
|
Caspofungin |
70 mg loading then 50 mg/day |
Duration of Antibiotics After Adequate Source Control
|
Clinical Scenario |
Recommended Duration |
|
Perforated appendicitis with source control |
3–5 days |
|
Perforated diverticulitis with source control |
4 days |
|
Generalized secondary peritonitis with adequate source control |
4 days |
|
Persistent sepsis or inadequate source control |
Individualized; continue until source controlled |