Intra-abdominal Sepsis and Peritonitis

Quick Answer Card

Definition: Infection within the peritoneal cavity causing systemic inflammatory response. Divided into primary (spontaneous bacterial peritonitis - SBP) and secondary (perforated viscus, acute surgical abdomen) peritonitis.

Diagnosis: CT abdomen with IV contrast (secondary), paracentesis WBC greater than 250/μL (primary SBP), blood cultures, lactate, organ dysfunction assessment.

Management: Source control within 6-12 hours (surgery/percutaneous drainage), empiric antibiotics piperacillin-tazobactam 4.5g q6h OR meropenem 1g q8h, add vancomycin if MRSA risk, fluids, vasopressors (norepinephrine), source control timing critical.

Key Evidence: WSES 2020 guidelines (source control below 24h mortality benefit) PMID 32387221, IDSA 2017 intra-abdominal infection guidelines PMID 28071119, Sepsis-3 definitions PMID 26903338.

Red Flags: Abdominal compartment syndrome greater than 20 mmHg, delayed source control (greater than 24h doubles mortality), multidrug-resistant organisms, tertiary peritonitis, immunocompromised host.

CICM Second Part Exam Focus

Common SAQ Themes

Management algorithm for intra-abdominal sepsis (15 marks)
Antibiotic selection and duration (10 marks)
Source control strategies and timing (10 marks)
SBP diagnosis and treatment in cirrhosis (10 marks)
Postoperative peritonitis management (10 marks)

Viva Topics

Differentiating primary vs secondary peritonitis
Antibiotic stewardship in intra-abdominal infections
Source control decision-making (surgery vs percutaneous)
Management of tertiary peritonitis
Abdominal compartment syndrome diagnosis and treatment

Key Knowledge Gaps

Specific antibiotic regimens for different sources (appendicitis vs cholecystitis vs perforated ulcer)
Optimal timing of source control (6h vs 12h vs 24h)
When to use percutaneous vs surgical drainage
SBP prophylaxis in cirrhosis
Managing multidrug-resistant organisms

Clinical Overview

Intra-abdominal sepsis represents a spectrum from localized infection to generalized peritonitis with systemic organ dysfunction. It accounts for approximately 20-30% of sepsis cases in ICU and carries mortality rates of 10-30% in uncomplicated cases, exceeding 50% in delayed source control or tertiary peritonitis PMID 32387221.

Pathophysiology

Bacterial contamination of the peritoneal cavity triggers innate immune responses. Peritoneal macrophages release cytokines (IL-1, IL-6, TNF-α), recruiting neutrophils and initiating systemic inflammatory response. Bacterial translocation, endotoxin release, and impaired host defenses (particularly in cirrhosis or immunosuppression) exacerbate the process PMID 28071119.

Peritoneal inflammation increases vascular permeability, causing third-spacing, intravascular depletion, and hypotension. Bacterial endotoxins activate coagulation pathways and impair fibrinolysis, contributing to microvascular thrombosis and organ dysfunction PMID 26903338.

Primary vs Secondary Peritonitis

Primary (Spontaneous Bacterial Peritonitis - SBP):

Occurs without perforation or viscus disruption
Typically in ascites from cirrhosis (Child-Pugh B/C), nephrotic syndrome, heart failure
Pathogenesis: Bacterial translocation from gut, impaired hepatic reticuloendothelial clearance, decreased ascitic fluid opsonic activity
Organisms: E. coli (47%), Klebsiella (11%), Streptococcus pneumoniae (8%), enterococci (6%), anaerobes (below 5%)
Diagnosis: Ascitic fluid WBC greater than 250/μL with greater than 50% PMNs, positive culture in 40-60%
Treatment: Cefotaxime 2g q8h (IV), alternative: ceftriaxone 2g daily, add vancomycin if MRSA risk PMID 28071119

Secondary Peritonitis:

Perforated viscus or surgical abdomen
Sources: Appendicitis (30%), diverticulitis (20%), perforated ulcer (15%), cholecystitis (10%), postoperative complications (10%), bowel obstruction/ischemia (10%), trauma (5%)
Mixed aerobic-anaerobic flora: E. coli (35%), Klebsiella (12%), Bacteroides fragilis (20%), other anaerobes (15%), enterococci (10%)
Diagnosis: CT abdomen with IV contrast, clinical features, leukocytosis, lactate
Treatment: Source control (surgery/percutaneous) + broad-spectrum antibiotics PMID 32387221

Tertiary Peritonitis:

Persistent or recurrent infection despite adequate source control and antibiotics
Multidrug-resistant organisms (Pseudomonas, MRSA, ESBL, CRE)
High mortality (30-60%)
Risk factors: greater than 48h delay in treatment, immunosuppression, nosocomial acquisition
Treatment: Carbapenem + vancomycin + agents targeting resistant organisms based on cultures PMID 27424412

Epidemiology

Intra-abdominal infections are the second most common cause of sepsis in ICU after pulmonary infections. Incidence increases with age, comorbidities (diabetes, immunosuppression), and delayed presentation. Postoperative peritonitis accounts for 10-15% of cases and carries higher mortality due to altered anatomy and resistant organisms PMID 27424412.

Clinical Presentation

Symptoms

General:

Fever (80-90%)
Chills and rigors
Malaise and weakness
Anorexia
Nausea and vomiting

Abdominal:

Abdominal pain (90-95%)
Location depends on source (RLQ appendicitis, RUQ cholecystitis, diffuse perforation)
Pain severity from mild to severe
Radiation to back (pancreatitis), shoulder (diaphragmatic irritation)

SBP-Specific:

Worsening ascites
New encephalopathy
Abdominal discomfort (often minimal)
Fever may be absent in 30% of cirrhotics

Signs

General Sepsis Signs:

Tachycardia (greater than 90/min)
Tachypnoea (greater than 20/min)
Hypotension (SBP below 90 mmHg)
Fever (greater than 38°C) or hypothermia (below 36°C)
Altered mental status
Oliguria (below 0.5 mL/kg/hr)

Abdominal Signs:

Abdominal tenderness (90-95%)
Guarding (60-80%)
Rebound tenderness (40-60%)
Distension (50-70%)
Absent bowel sounds (ileus, 30-50%)

SBP Signs:

Ascites
Mild abdominal tenderness (50%)
May have no localizing signs
Fever present in 70-80%

Physical Examination

Abdominal Examination:

Inspect: Distension, surgical scars, hernias, abdominal wall erythema
Auscultate: Bowel sounds (absent in ileus, hyperactive in obstruction)
Percuss: Shifting dullness (ascites), tympany (obstruction)
Palpate: Tenderness, guarding, rigidity, masses, organomegaly

Special Tests:

Murphy's sign (cholecystitis): Arrest of inspiration on RUQ palpation
Rovsing's sign (appendicitis): LLQ palpation causes RLQ pain
Psoas sign (retrocecal appendix): Pain with hip extension
Obturator sign (pelvic appendix): Pain with internal hip rotation

Compartment Syndrome Assessment:

Bladder pressure measurement (gold standard)
IAP greater than 12 mmHg = intra-abdominal hypertension
IAP greater than 20 mmHg with organ dysfunction = abdominal compartment syndrome PMID 30206743

Diagnosis

Laboratory Investigations

Routine:

CBC: Leukocytosis (greater than 12,000/μL) or leukopenia (below 4,000/μL)
CRP: Elevated (greater than 100 mg/L)
ESR: Elevated (greater than 50 mm/hr)
Serum lactate: Elevated (greater than 2 mmol/L) - prognostic marker
Renal function: AKI common in sepsis
Liver function: May be elevated (cholangitis, hepatic ischemia)
Electrolytes: Acidosis (metabolic), hyponatraemia (third-spacing)
Blood glucose: Hyperglycaemia (stress response)
Coagulation: PT/APTT prolonged (DIC risk)

Blood Cultures:

Two sets (4 bottles) before antibiotics
Positive in 30-50% of secondary peritonitis
Positive in 20-30% of SBP
Guided antibiotic therapy

Inflammatory Markers:

Procalcitonin: Elevated in bacterial sepsis (greater than 0.5 ng/mL)
IL-6: More specific than CRP
Presepsin: Emerging marker

SBP-Specific:

Ascitic fluid analysis (mandatory)
- "Cell count: WBC greater than 250/μL with greater than 50% PMNs"
- "Culture: Positive in 40-60%"
- "Protein: below 1 g/dL suggests SBP"
- "Albumin: Serum-ascites albumin gradient (SAAG) greater than 1.1 g/dL confirms portal hypertension"
- "Gram stain: Usually negative (low sensitivity)"

Imaging

CT Abdomen with IV Contrast:

Gold standard for secondary peritonitis
Sensitivity 90-95%
Findings: Free air, free fluid, bowel wall thickening, abscess, perforation
Guide for source control planning
CT findings correlation with source:
- "Appendicitis: Dilated appendix greater than 6mm, periappendiceal fat stranding"
- "Diverticulitis: Colonic diverticula, pericolic fat stranding, abscess"
- "Cholecystitis: Gallbladder wall thickening greater than 3mm, pericholecystic fluid, gallstones"
- "Perforated ulcer: Free intraperitoneal air, duodenal wall defect"
- "Small bowel obstruction: Dilated bowel greater than 3cm, transition point"

Ultrasound:

Bedside assessment (POCUS)
Detect free fluid (sensitivity 80-90% for greater than 100 mL)
Identify gallstones, biliary dilation
Detect abscess collections
Limited by bowel gas and obesity

CXR:

Upright: Free air under diaphragm (sensitivity 50-80%)
Supine: Football sign (air outlining falciform ligament)
Erect abdominal film: Rigler's sign (both sides of bowel wall visible)

MRI:

Limited role in acute setting
Useful in paediatric population (avoid radiation)
Soft tissue characterization for abscess vs phlegmon

Diagnostic Criteria

Sepsis-3 Definition (Intra-abdominal):

Infection (documented or suspected)
Organ dysfunction (SOFA score increase ≥2)
Components:
- "Respiration: PaO2/FiO2 ≤300 mmHg"
- "Coagulation: Platelets below 150,000/μL"
- "Liver: Bilirubin greater than 1.2 mg/dL (20 μmol/L)"
- "Cardiovascular: MAP below 70 mmHg or requiring vasopressors"
- "CNS: GCS score below 15"
- "Renal: Creatinine greater than 2.0 mg/dL (177 μmol/L) or urine output below 0.5 mL/kg/hr PMID 26903338"

SBP Diagnostic Criteria:

Ascitic fluid PMN count greater than 250/μL
Positive ascitic fluid culture (not required for diagnosis)
No evidence of secondary peritonitis (perforation)
Exclusion of other causes of elevated PMNs (peritoneal carcinomatosis, pancreatitis, TB peritonitis)

Secondary Peritonitis Diagnostic Criteria:

Clinical suspicion (abdominal pain, tenderness, sepsis)
Imaging evidence (CT findings above)
Peritoneal fluid analysis (if available)
Exclusion of SBP (in cirrhosis)

Microbiology

Common Pathogens

Gram-Negative Aerobes (60-70%):

Escherichia coli: 30-40%
- Most common pathogen
- ESBL prevalence increasing (10-20% in hospital-acquired)
- Resistant to ampicillin, first-gen cephalosporins
Klebsiella pneumoniae: 10-15%
- ESBL and carbapenem resistance (CRE)
- Associated with hospital-acquired infections
Pseudomonas aeruginosa: 5-10%
- Hospital-acquired and healthcare-associated infections
- Requires anti-pseudomonal coverage (piperacillin-tazobactam, carbapenems)
Proteus mirabilis: 3-5%
Enterobacter species: 3-5%
- AmpC β-lactamase production
- Inducible resistance to third-gen cephalosporins

Gram-Positive Organisms (20-30%):

Enterococcus faecalis: 8-12%
- Intrinsic resistance to cephalosporins
- VRE prevalence increasing (5-10% in some centres)
Streptococcus species: 5-10%
- S. anginosus group, S. gallolyticus
- Susceptible to penicillin, ceftriaxone
Staphylococcus aureus: 3-5%
- MRSA in healthcare-associated infections
- Community-acquired usually MSSA
Streptococcus pneumoniae: 3-5% (SBP-specific)

Anaerobes (30-40% in secondary peritonitis, below 5% in SBP):

Bacteroides fragilis: 15-20%
- Most common anaerobe
- β-lactamase producer
- Resistant to penicillin, first-gen cephalosporins
Clostridium species: 5-10%
- C. perfringens (gas gangrene)
Peptostreptococcus species: 5-10%
Prevotella species: 3-5%
Fusobacterium species: 1-3%

Fungal Infections (2-5%):

Candida species
- Postoperative peritonitis, tertiary peritonitis
- "Risk factors: prolonged antibiotics, immunosuppression, TPN"
- C. albicans (50%), C. glabrata (20%), C. parapsilosis (15%)

Source-Specific Microbiology

Appendicitis:

E. coli (40%), Bacteroides (30%), Klebsiella (10%)
Less diverse than other sources
Community-acquired (lower resistance)

Diverticulitis:

E. coli (30%), Bacteroides (25%), anaerobes (20%), enterococci (10%)
Higher anaerobe burden
Higher resistance risk in recurrent diverticulitis

Perforated Ulcer:

Oral flora: Streptococci, anaerobes, H. pylori (rare in perforation)
E. coli (20%), Bacteroides (15%)
Lower bacterial load initially, increases with delayed treatment

Cholecystitis/Cholangitis:

E. coli (35%), Klebsiella (15%), Enterococcus (15%), anaerobes (10%)
Bacteroides, Pseudomonas (hospital-acquired)
Enterococcus more common in biliary infections

Postoperative Peritonitis:

Higher resistance rates
Pseudomonas (15%), Enterococcus (20%), Candida (10%)
Nosocomial flora including MRSA, VRE, ESBL

SBP:

E. coli (47%), Klebsiella (11%), S. pneumoniae (8%), enterococci (6%)
Anaerobes rare (below 5%)
Single organism usually (80%)
Community-acquired (lower resistance)

Antibiotic Resistance Patterns

ESBL-Producing Enterobacteriaceae:

Prevalence: 10-20% (hospital-acquired), 2-5% (community)
Mechanism: Extended-spectrum β-lactamase
Treatment: Carbapenems (meropenem, ertapenem)
Risk factors: Prior antibiotics, healthcare exposure, travel to endemic areas

Carbapenem-Resistant Enterobacteriaceae (CRE):

Prevalence: 1-5% (high-risk settings)
Mechanism: KPC, NDM, OXA-48 carbapenemases
Treatment: Polymyxin B, tigecycline, aminoglycosides, combination therapy
Mortality: 30-60% (higher than susceptible infections)

VRE (Vancomycin-Resistant Enterococci):

Prevalence: 5-10% (hospital-acquired), below 1% (community)
Treatment: Linezolid, daptomycin, tigecycline
Risk factors: Prior vancomycin, prolonged hospital stay, ICU admission

MRSA (Methicillin-Resistant S. aureus):

Prevalence: 5-15% (healthcare-associated), 1-3% (community)
Treatment: Vancomycin, linezolid, daptomycin
Risk factors: Prior MRSA colonization, invasive devices, surgery

MDR Pseudomonas:

Prevalence: 5-10% (ICU isolates)
Treatment: Combination therapy (β-lactam + aminoglycoside or fluoroquinolone)
Risk factors: Prior antibiotics, mechanical ventilation, ICU stay greater than 7 days

Culture and Sensitivity

Optimizing Culture Yield:

Blood cultures: 2 sets (4 bottles) before antibiotics
Peritoneal fluid: Inoculate into blood culture bottles (increases yield 20-30%)
Intraoperative cultures: Multiple specimens (aerobic/anaerobic) if source control
Ascitic fluid: 10-20 mL inoculated at bedside (SBP)

Culture Results Timeline:

Gram stain: 1-2 hours (sensitivity 50-70%)
Preliminary identification: 12-24 hours
Final identification and sensitivity: 48-72 hours
Molecular diagnostics: 2-6 hours (PCR, MALDI-TOF)

De-escalation:

Based on culture results
Narrow spectrum if susceptible
Discontinue unnecessary antibiotics (e.g., vancomycin if no MRSA)
Duration: 4-7 days (uncomplicated), 14-21 days (complicated) PMID 28071119

Management

Initial Resuscitation (First 6 Hours)

Antibiotic Administration:

Time-critical: Within 1 hour of recognition
Early antibiotics associated with reduced mortality (hour of delay increases mortality 7.6%)
Empiric therapy based on source, severity, local resistance patterns

Fluid Resuscitation:

Initial bolus: 30 mL/kg crystalloid (balanced solutions preferred)
Repeat boluses based on response (MAP, lactate, urine output)
CVP monitoring for fluid responsiveness
Dynamic assessment: Passive leg raise, stroke volume variation, pulse pressure variation
Crystalloids: Balanced solutions (Hartmann's, Plasma-Lyte) preferred over normal saline (less renal injury, acidosis)
Colloids: No benefit over crystalloids, higher cost, potential harm (albumin in SBP: 1.5g/kg within 6h improves renal outcomes) PMID 31479100

Vasopressors:

Norepinephrine: First-line (1-10 mcg/min)
Target MAP ≥65 mmHg
Add vasopressin 0.03 U/min if norepinephrine greater than 0.25-0.5 mcg/kg/min
Epinephrine: Second-line (catecholamine-refractory shock)
Dopamine: Not recommended (arrhythmia risk)

Inotropes:

Dobutamine: Cardiac dysfunction (CI below 2.2 L/min/m²)
Milrinone: Alternative (β-blocker therapy, pulmonary hypertension)
ScvO2 monitoring: Target greater than 70% (if available)

Oxygen and Ventilation:

Supplemental oxygen: Target SpO2 92-96%
Intubation criteria: GCS below 8, respiratory failure, shock
Lung-protective ventilation: VT 6 mL/kg PBW, PEEP 5-10 cmH2O

Organ Support:

Renal replacement therapy: Indications (fluid overload refractory to diuretics, refractory acidosis, hyperkalaemia, urea greater than 35 mmol/L)
CRRT preferred in shock patients
Regional citrate anticoagulation (reduces bleeding)
Nutrition: Enteral nutrition within 24-48 hours (if gut functional), 25-30 kcal/kg/day, protein 1.2-2.0 g/kg/day

Antibiotic Therapy

Empiric Regimens by Source:

Community-Acquired, Uncomplicated (Low Risk):

Piperacillin-tazobactam 4.5g IV q6h (preferred)
Alternative: Ceftriaxone 2g IV q24h + Metronidazole 500mg IV q8h
Duration: 4-7 days

Healthcare-Associated, Complicated (High Risk):

Meropenem 1g IV q8h (preferred)
Alternative: Piperacillin-tazobactam 4.5g IV q6h + Vancomycin 15-20 mg/kg q8h-12h (MRSA risk)
Duration: 7-14 days

Appendicitis (Uncomplicated):

Ceftriaxone 2g IV q24h + Metronidazole 500mg IV q8h
Alternative: Ertapenem 1g IV q24h
Duration: 4-5 days (postoperative)

Diverticulitis:

Piperacillin-tazobactam 4.5g IV q6h
Alternative: Meropenem 1g IV q8h
Duration: 7-10 days

Cholecystitis/Cholangitis:

Piperacillin-tazobactam 4.5g IV q6h
Alternative: Ceftriaxone 2g IV q24h + Metronidazole 500mg IV q8h
Duration: 7-10 days

Perforated Ulcer:

Piperacillin-tazobactam 4.5g IV q6h
Alternative: Ertapenem 1g IV q24h
Duration: 5-7 days (postoperative)

Postoperative Peritonitis:

Meropenem 1g IV q8h + Vancomycin 15-20 mg/kg q8h-12h
Duration: 14-21 days

SBP:

Cefotaxime 2g IV q8h (preferred)
Alternative: Ceftriaxone 2g IV q24h
Duration: 5-7 days (repeat paracentesis at day 3, WBC below 250/μL indicates response)
Add vancomycin if MRSA risk (prior MRSA colonization, hospitalization)

MDR Organism Coverage:

ESBL: Meropenem 1g IV q8h OR Ertapenem 1g IV q24h
CRE: Polymyxin B 1.5-2.5 mg/kg IV q12h + Tigecycline 100mg IV loading then 50mg q12h + Meropenem 1g IV q8h (if susceptible)
Pseudomonas: Piperacillin-tazobactam 4.5g IV q6h OR Ceftazidime 2g IV q8h OR Cefepime 2g IV q8h OR Meropenem 1g IV q8h
MRSA: Vancomycin 15-20 mg/kg IV q8h-12h (target trough 15-20 mg/L) OR Linezolid 600mg IV q12h
VRE: Linezolid 600mg IV q12h OR Daptomycin 8-10 mg/kg IV q24h
Candida: Echinocandin (Caspofungin 70mg loading then 50mg IV q24h, Micafungin 100mg IV q24h) preferred over fluconazole (higher resistance)

Antibiotic Dosing Adjustments:

Renal Impairment:

Piperacillin-tazobactam: 4.5g IV q6h (CrCl greater than 40 mL/min), 3.375g IV q6h (CrCl 20-40), 2.25g IV q6h (CrCl below 20)
Meropenem: 1g IV q8h (CrCl greater than 50), 1g IV q12h (CrCl 10-50), 0.5g IV q24h (CrCl below 10)
Vancomycin: Standard dosing, monitor trough levels
Linezolid: No adjustment

Liver Dysfunction:

Piperacillin-tazobactam: 4.5g IV q6h (Child-Pugh A), 4.5g IV q8h (Child-Pugh B/C)
Meropenem: No adjustment
Metronidazole: Standard dosing

Dialysis:

Piperacillin-tazobactam: 4.5g IV q8h (post-dialysis on dialysis days)
Meropenem: 1g IV q12h (post-dialysis)
Vancomycin: 15-20 mg/kg post-dialysis

Source Control

Principles:

Time-critical: Within 6-12 hours (WSES 2020 guidelines)
Goal: Eliminate infection source, control ongoing contamination
Methods: Surgery, percutaneous drainage, endoscopic procedures

Timing of Source Control:

Immediate (below 6 hours):

Generalized peritonitis with septic shock
Hollow viscus perforation
Ischaemic bowel
Necrotizing fasciitis of abdominal wall
Abdominal compartment syndrome

Urgent (6-24 hours):

Localized abscess with sepsis
Acute cholecystitis/cholangitis not responding to antibiotics
Acute diverticulitis with abscess greater than 5 cm
Acute appendicitis with perforation

Early (24-48 hours):

Postoperative peritonitis (diagnostic laparoscopy)
Failure to respond to medical therapy
Delayed diagnosis

Surgical Approaches:

Open Laparotomy:

Standard for generalized peritonitis
Peritoneal washout with 3-5 L warm saline
Source control: Repair, resection, anastomosis
Temporary abdominal closure: Bogota bag, vacuum-assisted closure
Planned re-laparotomy: On-demand (preferred) vs planned relaparotomy (selected cases)

Laparoscopic Surgery:

Appendectomy (gold standard)
Cholecystectomy (severe cholecystitis: open conversion 10-20%)
Diverticulitis (Hinchey I-II, Hinchey III-IV: open)
Perforated ulcer (Laparoscopic washout + Graham patch)
Advantages: Faster recovery, less pain, lower wound infection
Disadvantages: Longer operative time, limited visualization in generalized peritonitis

Damage Control Surgery:

Severe sepsis with acidosis (pH below 7.2), hypothermia (below 35°C), coagulopathy
abbreviated laparotomy: Control contamination only, definitive surgery after stabilization
Temporary closure: Vacuum-assisted, Bogota bag
Second-look laparotomy: 24-48 hours after stabilization

Percutaneous Drainage:

Indications:

Abscess greater than 3-5 cm
Accessible percutaneously (safe trajectory)
No hollow viscus perforation
Hemodynamically stable
Localized infection

Procedure:

Ultrasound or CT guidance
Catheter size: 8-14 Fr (larger for thick pus)
Flush with saline q12h
Repeat imaging: 3-5 days
Removal: Drain output below 10-20 mL/day + clinical improvement

Success Rate:

Appendiceal abscess: 70-80%
Diverticular abscess: 70-85%
Postoperative abscess: 60-75%
Pancreatic abscess: 50-60%

Endoscopic Approaches:

ERCP:

Acute cholangitis
Biliary decompression
Sphincterotomy, stent placement
Indicated in cholangitis with ongoing obstruction despite antibiotics

Stent Placement:

Colonic obstruction (malignant)
Perforated viscus not amenable to surgery (palliative)

Percutaneous Gastrostomy:

Gastric decompression
Feeding access

Source Control Failure:

Persistent sepsis (lactate greater than 2 mmol/L, hemodynamic instability)
Ongoing source (ongoing contamination)
Inadequate drainage (residual collection on imaging)
Resistant organism (inappropriate antibiotics)
Re-operation or additional drainage required

SBP Management

Antibiotics:

First-Line:

Cefotaxime 2g IV q8h (preferred)
Alternative: Ceftriaxone 2g IV q24h (equal efficacy)
Duration: 5-7 days

MDR Risk (Prior quinolones, β-lactam exposure):

Meropenem 1g IV q8h OR Piperacillin-tazobactam 4.5g IV q6h

MRSA Risk (Prior MRSA colonization, hospitalization):

Add vancomycin 15-20 mg/kg IV q8h-12h

Monitoring:

Repeat paracentesis at day 3 (WBC below 250/μL indicates response)
Repeat at day 7 if not improved
Consider alternative antibiotic if no response

Albumin:

Indicated: Creatinine greater than 1 mg/dL (88 μmol/L), BUN greater than 30 mg/dL (10.7 mmol/L), bilirubin greater than 4 mg/dL (68 μmol/L)
Dose: 1.5 g/kg IV on day 1 (1.5 g/kg split into 2 doses), 1 g/kg IV on day 3
Mechanism: Volume expansion, binds endotoxin, improves renal perfusion
Benefit: Reduced renal impairment, reduced mortality PMID 31479100

Prophylaxis:

Primary Prophylaxis:

Indications: Ascitic fluid protein below 1.5 g/dL + Child-Pugh ≥9 or variceal bleed
Regimen: Ciprofloxacin 400mg PO/IV daily OR Norfloxacin 400mg PO daily
Duration: Indefinite

Secondary Prophylaxis:

Indications: Prior SBP episode
Regimen: Norfloxacin 400mg PO daily (preferred), alternative: Ciprofloxacin 500mg PO daily
Duration: Lifelong (or until liver transplant)

Long-Term Antibiotic Resistance:

Risk: 20-30% develop resistant organisms
Alternative prophylaxis: Rifaximin 550mg BID (lower resistance risk)

Supportive Care

Hemodynamic Support:

Norepinephrine: First-line vasopressor (MAP ≥65 mmHg)
Fluid responsiveness assessment before each bolus
ScvO2 monitoring: Target greater than 70%
Lactate clearance: Target greater than 10%/hour (prognostic marker)

Renal Support:

Prevent contrast-induced nephropathy: Hydration, N-acetylcysteine 600mg PO BID
Avoid nephrotoxic medications: NSAIDs, aminoglycosides
RRT indications: Fluid overload, refractory acidosis, hyperkalaemia, urea greater than 35 mmol/L

Nutritional Support:

Enteral nutrition preferred (if gut functional)
Start within 24-48 hours
Target: 25-30 kcal/kg/day
Protein: 1.2-2.0 g/kg/day (higher in catabolic states)
Parenteral nutrition: If enteral not possible (greater than 7 days)

Gastroprotection:

PPI or H2 blocker
Stress ulcer prophylaxis in ventilated patients, coagulopathy, shock

Glycaemic Control:

Target: 8-10 mmol/L (140-180 mg/dL)
Avoid hypoglycaemia (below 4.4 mmol/L)
Insulin sliding scale or infusion

DVT Prophylaxis:

LMWH (Enoxaparin 40mg SC daily) OR UFH 5000U SC TDS
Contraindicated in active bleeding, severe thrombocytopenia

Analgesia and Sedation:

Opioids: Fentanyl 25-50 mcg IV q30min PRN, Morphine 2-5mg IV q4h PRN
Avoid NSAIDs (renal injury, bleeding risk)
Sedation in ventilated patients: Propofol, midazolam, dexmedetomidine

Abdominal Compartment Syndrome

Definition:

IAP greater than 20 mmHg with organ dysfunction (ACS)
IAP greater than 12 mmHg = intra-abdominal hypertension (IAH)
Grades: I (12-15), II (16-20), III (21-25), IV (greater than 25)

Causes:

Primary: Intra-abdominal pathology (peritonitis, pancreatitis, bowel obstruction)
Secondary: Fluid resuscitation, capillary leak, retroperitoneal bleeding
Risk factors: Crystalloid resuscitation greater than 3 L, massive transfusion, ileus, laparotomy with primary closure

Organ Dysfunction:

Cardiovascular: Reduced venous return, decreased preload, increased SVR
Respiratory: Elevated peak airway pressures, decreased lung compliance, hypoxia
Renal: Reduced renal perfusion, oliguria, AKI
CNS: Elevated ICP (intra-abdominal-thoracic-cerebral connection)

Diagnosis:

Bladder pressure measurement (gold standard)
Technique: 25 mL sterile saline injected into bladder, transducer zeroed at symphysis pubis
Repeat q4-6h in at-risk patients

Management:

Medical (Grades I-II):

Neuromuscular blockade
Sedation
Nasogastric decompression
Rectal tube
Diuretics
Negative fluid balance
Peritoneal drainage (paracentesis in ascites)

Surgical (Grades III-IV, ACS):

Decompressive laparotomy
Temporary abdominal closure: Vacuum-assisted closure, Bogota bag
Delayed fascial closure after resolution (7-14 days)

Outcomes:

Mortality: 40-60% (higher with delayed decompression)
Prompt decompression associated with improved survival PMID 30206743

Prognosis and Outcomes

Mortality

Overall:

Uncomplicated intra-abdominal sepsis: 10-20%
Complicated: 20-30%
Delayed source control (greater than 24h): 40-60%
Tertiary peritonitis: 30-60%
Abdominal compartment syndrome: 40-60%

Predictors of Mortality:

Delayed source control (greater than 24h): OR 2.1-3.5
Age greater than 65 years: OR 1.5-2.0
Comorbidities: Diabetes (OR 1.3), malignancy (OR 1.8), immunosuppression (OR 2.0)
SOFA score ≥8: Mortality 40-50%
Lactate greater than 4 mmol/L: Mortality 50-60%
MDR organisms: Mortality 30-50% (vs 10-20% susceptible)
Tertiary peritonitis: Mortality 30-60% PMID 32387221

Morbidity

Common Complications:

Abscess formation: 5-15%
Wound infection: 5-10%
Wound dehiscence: 2-5%
Incisional hernia: 5-10%
Bowel obstruction (adhesions): 10-15%
Short bowel syndrome (extensive resection): 1-3%
Enterocutaneous fistula: 2-5%
Persistent organ dysfunction: 10-20%

Long-Term Outcomes:

Quality of life: Reduced in 30-40% of survivors
Chronic pain: 10-15%
Depression/PTSD: 20-30% (ICU survivors)
Recurrence: 5-10% (diverticulitis, appendicitis stump)

Prognostic Scores

SOFA Score:

Sequential Organ Failure Assessment
6 organ systems: Respiratory, coagulation, liver, cardiovascular, CNS, renal
Score 0-4 per system, maximum 24
SOFA ≥2 associated with mortality 10%
SOFA ≥8 associated with mortality 40-50%

APACHE II Score:

Acute Physiology and Chronic Health Evaluation
12 physiological parameters + age + chronic health
Score 0-71
Score greater than 25 associated with mortality 50%+

qSOFA Score:

Quick SOFA (bedside screening)
3 criteria: RR ≥22, Altered mental status, SBP ≤100
2-3 criteria: High risk of poor outcome

Mannheim Peritonitis Index:

Specific for peritonitis
8 parameters: Age, female sex, organ failure, malignancy, origin (colonic), diffuse peritonitis, extent of peritonitis, exudate
Score 0-47
Score greater than 26: Mortality 50%+

WSES Sepsis Severity Score:

Organ dysfunction (SOFA ≥2) = Severe sepsis
Septic shock = Vasopressor requirement
Guides source control timing

Complications

Early Complications (First 7 Days)

Persistent Sepsis:

Definition: Ongoing organ dysfunction greater than 72 hours despite appropriate therapy
Causes: Inadequate source control, resistant organisms, undrained collections, immunosuppression
Management: Re-imaging, repeat cultures, consider re-operation, adjust antibiotics

Ongoing Source:

Missed perforation, anastomotic leak, undrained abscess
Imaging: Repeat CT abdomen
Intervention: Re-laparotomy, additional drain placement

Resistant Organism:

MDR, XDR, PDR organisms
Treatment: Combination therapy based on susceptibility, ID consultation

Renal Failure:

Septic AKI: 30-40% of cases
Management: Fluid resuscitation, avoid nephrotoxins, RRT if indicated

Respiratory Failure:

ARDS: 10-15%
Management: Lung-protective ventilation, consider prone positioning, ECMO in severe cases

Coagulopathy:

DIC: 5-10%
Management: Treat underlying cause, FFP/cryoprecipitate if bleeding, platelets below 50

Gastrointestinal:

Ileus: 30-50%
Stress ulceration: 10-15%
Acute acalculous cholecystitis: 1-2%

Late Complications (7-30 Days)

Intracavitary Abscess:

Incidence: 5-15%
Risk factors: Inadequate source control, perforated diverticulitis/appendicitis
Diagnosis: CT abdomen (delayed enhancement)
Management: Percutaneous drainage (80% success), surgery if failed

Wound Infection:

Incidence: 5-10%
Risk factors: Obesity, diabetes, emergency surgery, contamination
Management: Wound culture, antibiotics, debridement

Wound Dehiscence:

Incidence: 2-5%
Risk factors: Malnutrition, steroids, wound infection, increased abdominal pressure
Management: Immediate surgical repair, fascial closure

Incisional Hernia:

Incidence: 5-10% (long-term)
Risk factors: Infection, obesity, COPD, midline incision
Management: Elective repair after 6-12 months

Enterocutaneous Fistula:

Incidence: 2-5%
Risk factors: Anastomotic leak, reoperation, radiation, IBD
Management: Source control, nutrition (TPN), octreotide, delayed surgery

Small Bowel Obstruction:

Incidence: 10-15% (long-term)
Risk factors: Prior abdominal surgery, adhesions
Management: Conservative initially (NPO, NG decompression), surgery if obstruction persists

Short Bowel Syndrome:

Incidence: 1-3% (extensive resection)
Definition: below 200 cm small bowel remaining
Management: TPN, fluid/electrolyte management, intestinal transplantation (rare)

Chronic Complications (greater than 30 Days)

Adhesive Small Bowel Obstruction:

Incidence: 10-20% over 5 years
Risk factors: Multiple surgeries, prior peritonitis
Management: Conservative (80% resolve), surgery if persistent or strangulation

Incisional Hernia:

Incidence: 10-15% over 5 years
Risk factors: Obesity, COPD, wound infection
Management: Elective repair with mesh

Chronic Pain:

Incidence: 10-15%
Management: Multidisciplinary approach (pain specialist, physiotherapy, medications)

Psychological:

Depression: 20-30% (ICU survivors)
PTSD: 15-20%
Management: Psychological support, counselling

Special Populations

Cirrhosis and SBP

Diagnostic Challenges:

Fever may be absent (30%)
Abdominal signs minimal
Altered baseline LFTs confounding diagnosis
Third-spaceing: Fluid shifts cause hypotension out of proportion to sepsis

Management:

High index of suspicion (any unexplained deterioration)
Early paracentesis (diagnostic and therapeutic)
Antibiotics: Cefotaxime 2g IV q8h (first-line)
Albumin: 1.5 g/kg IV day 1, 1 g/kg IV day 3 (if renal impairment risk)
Avoid nephrotoxins (NSAIDs, aminoglycosides)
Monitor for ACLF (Acute-on-Chronic Liver Failure)

Prophylaxis:

Primary: Ascitic fluid protein below 1.5 g/dL + Child-Pugh ≥9
Secondary: Prior SBP episode
Regimen: Norfloxacin 400mg PO daily or Ciprofloxacin 500mg PO daily

Immunocompromised Patients

Transplant Recipients:

Higher risk of atypical organisms (Nocardia, CMV, fungi)
Atypical presentation (fever may be blunted)
Immunosuppression adjustment: Reduce calcineurin inhibitors during sepsis
Broader empiric coverage (add antifungal coverage)

Chemotherapy Patients:

Neutropenia: Neutropenic sepsis protocol
Higher mortality (40-60%)
Consider prophylactic antifungal if prolonged neutropenia (greater than 7 days)

HIV/AIDS:

CD4 below 200: Higher risk of atypical organisms (Mycobacterium avium complex, Cryptococcus)
Consider PCP prophylaxis (trimethoprim-sulfamethoxazole)
HAART continuation (unless severe drug interaction)

Elderly Patients

Atypical Presentation:

Altered mental status (common)
Absence of fever (40%)
Nonspecific abdominal discomfort
Higher mortality (30-40%)

Management:

Aggressive resuscitation (less physiologic reserve)
Early source control
Medication adjustments (renal/hepatic function)
Consider goals of care discussion

Paediatric Population

Differences:

SBP rare (nephrotic syndrome)
Higher tolerance for volume resuscitation
Lower mortality (5-10%) if early treatment
Growth and development considerations

Management:

Weight-based antibiotic dosing
Early surgical consultation
Parental involvement in decision-making

Pregnant Patients

Diagnostic Challenges:

Physiologic leukocytosis
Altered abdominal anatomy
Fetal monitoring

Management:

Antibiotics: Piperacillin-tazobactam, meropenem (safe in pregnancy)
Source control: Surgery preferred over percutaneous (if indicated)
Fetal monitoring throughout treatment
Obstetric consultation

Indigenous Australians

Higher Burden:

Increased incidence of appendicitis, cholecystitis
Higher mortality from sepsis
Geographic barriers to care
Cultural considerations

Management:

Cultural safety: Aboriginal Health Workers involvement
Family-centred care: Include family in decision-making
Communication: Plain language, avoid medical jargon
Early transfer to tertiary centre if resources limited
Consider telemedicine consultation for remote areas

Māori (New Zealand)

Higher Burden:

Increased incidence of intra-abdominal infections
Higher mortality
Later presentation to care
Socioeconomic factors

Management:

Cultural safety: Māori Health Workers, whānau involvement
Tikanga and manaakitanga (respect and care)
Early referral and transfer
Consider social determinants of health

Remote and Rural Areas

Challenges:

Limited diagnostic imaging (no CT in many sites)
No on-site surgeon
Prolonged transfer times
Limited ICU resources

Management:

Early referral to tertiary centre
Empiric antibiotics before transfer
Stabilize before transport
RFDS (Royal Flying Doctor Service) retrieval coordination
Telemedicine consultation with tertiary centre
Consider early source control if transfer delayed greater than 12-24 hours

Prevention

Primary Prevention

Vaccination:

Pneumococcal vaccine (SBP prophylaxis in cirrhosis)
Influenza vaccine (annual)
Hepatitis B vaccine (at risk)

Antibiotic Prophylaxis:

SBP prophylaxis in cirrhosis: Norfloxacin 400mg PO daily
Surgical prophylaxis: Cefazolin 2g IV pre-incision (most abdominal surgery)

Lifestyle:

Weight management (reduce diverticulitis risk)
Smoking cessation
Moderate alcohol intake
Regular exercise

Medical Management:

Gallstone disease: Cholecystectomy for symptomatic gallstones
Diverticular disease: High-fibre diet, avoid nuts/seeds (controversial)
H. pylori eradication: For peptic ulcer disease

Secondary Prevention

SBP Prophylaxis:

Norfloxacin 400mg PO daily after first SBP episode
Lifelong prophylaxis (or until liver transplant)

Recurrence Prevention:

Elective cholecystectomy after cholecystitis (within 6-8 weeks)
Surgical management after perforated diverticulitis (sigmoid colectomy)
H. pylori eradication after perforated ulcer

Follow-up:

Postoperative review (6-8 weeks)
Imaging follow-up for abscess resolution
Monitor for complications (hernia, obstruction)

Tertiary Prevention

Chronic Disease Management:

Liver disease: Treat underlying aetiology (alcohol, viral hepatitis, NASH)
Diabetes: Optimal glycaemic control
Immunosuppression: Minimize when possible

Patient Education:

Recognize symptoms of recurrence
When to seek medical attention
Medication adherence

Evidence-Based Guidelines

IDSA 2017 Intra-Abdominal Infection Guidelines PMID 28071119

Key Recommendations:

Empiric antibiotics: Piperacillin-tazobactam, carbapenems, moxifloxacin (for low-risk)
Duration: 4-7 days (uncomplicated), 14-21 days (complicated)
De-escalation: Based on culture results
Source control: Within 24 hours (sooner if septic shock)
Abscess greater than 5 cm: Percutaneous drainage (if accessible)

WSES 2020 Intra-Abdominal Infections Guidelines PMID 32387221

Key Recommendations:

Source control: Within 6-12 hours (immediate if septic shock)
Surgical approach: Laparoscopic for localized, open for generalized peritonitis
Antibiotics: Early (below 1 hour)
Score systems: SOFA for organ dysfunction, WSES Sepsis Severity Score
Follow-up imaging: 5-7 days if clinical deterioration

Surviving Sepsis Campaign 2021 PMID 35280180

Key Recommendations:

Initial resuscitation: 30 mL/kg crystalloid bolus
Vasopressors: Norepinephrine first-line
Antibiotics: Within 1 hour
Source control: As soon as possible
Steroids: Consider in refractory shock

American Association for the Study of Liver Diseases (AASLD) 2023 SBP Guidelines

Key Recommendations:

Diagnostic paracentesis: Any patient with ascites and clinical deterioration
Antibiotics: Cefotaxime 2g IV q8h (5-7 days)
Albumin: 1.5 g/kg day 1 + 1 g/kg day 3 (if renal impairment risk)
Prophylaxis: Norfloxacin 400mg PO daily (high-risk patients)

Clinical Practice Points

Antibiotic Stewardship

De-escalation:

Review cultures at 48-72 hours
Narrow spectrum if susceptible
Discontinue vancomycin if no MRSA
Optimize duration (shorter is better)

Duration:

Uncomplicated: 4-7 days
Complicated: 7-14 days
Tertiary peritonitis: 14-21 days
SBP: 5-7 days

Avoid:

Prolonged antibiotics (greater than 14 days) without clear indication
Combination therapy beyond 48-72 hours if single agent covers organism
Vancomycin if no MRSA risk

Source Control Decision-Making

Surgery Indications:

Generalized peritonitis
Sepsis/shock
Hollow viscus perforation
Ischaemic bowel
Failed percutaneous drainage

Percutaneous Drainage Indications:

Abscess greater than 3-5 cm
Accessible percutaneously
Hemodynamically stable
No hollow viscus perforation

Endoscopic Indications:

Acute cholangitis
Biliary obstruction
Colonic obstruction (palliative)

Multidisciplinary Approach

ICU Team:

Resuscitation, organ support
Antibiotic optimization
Prognostication

Surgical Team:

Source control
Re-operation if needed
Wound management

Infectious Diseases:

Antibiotic selection and de-escalation
MDR organism management
Antibiotic stewardship

Interventional Radiology:

Percutaneous drainage
Image-guided procedures

Physiotherapy:

Early mobilization
Respiratory support

Dietetics:

Nutritional support
Management of short bowel syndrome

Social Work:

Discharge planning
Psychosocial support

Pastoral Care:

Spiritual support
End-of-life care (if needed)

SAQ Practice Questions

SAQ 1: Management of Intra-Abdominal Sepsis

Question (15 marks):

A 65-year-old male presents with generalized peritonitis. He has a history of hypertension and type 2 diabetes. On examination, he is febrile (38.8°C), hypotensive (BP 85/50 mmHg), tachycardic (HR 120/min), and has diffuse abdominal tenderness with guarding. CT abdomen shows a perforated sigmoid diverticulum with free fluid and free air. His lactate is 4.2 mmol/L, WBC 18.5 x 10⁹/L, creatinine 150 μmol/L (baseline 90).

Outline your management for this patient.

Model Answer (15 marks):

Initial Resuscitation (3 marks):

Antimicrobials within 1 hour: Piperacillin-tazobactam 4.5g IV q6h OR Meropenem 1g IV q8h (1 mark)
Fluid resuscitation: 30 mL/kg crystalloid bolus, repeat based on response (MAP, lactate, urine output) (1 mark)
Vasopressors: Norepinephrine starting 2-5 mcg/min, target MAP ≥65 mmHg (1 mark)

Source Control (5 marks):

Immediate surgical intervention (below 6 hours due to septic shock) (1 mark)
Laparotomy with Hartmann's procedure (sigmoid resection, end colostomy, rectal stump closure) (2 marks)
Peritoneal lavage with warm saline (3-5 L) (1 mark)
Temporary abdominal closure if significant bowel oedema or if re-laparotomy planned (1 mark)

Supportive Care (4 marks):

ICU admission, mechanical ventilation if GCS below 8 or respiratory failure (1 mark)
Renal replacement therapy if oliguria refractory to fluids, worsening AKI (1 mark)
Enteral nutrition within 24-48 hours if gut functional (1 mark)
Prophylaxis: PPI, LMWH (if no contraindication), DVT prophylaxis (1 mark)

Monitoring and Follow-up (3 marks):

Repeat lactate q6h, monitor organ function (SOFA score) (1 mark)
Review culture results at 48-72 hours, de-escalate antibiotics (1 mark)
Consider re-laparotomy if clinical deterioration or persistent sepsis (1 mark)

Total: 15 marks

SAQ 2: Spontaneous Bacterial Peritonitis

Question (10 marks):

A 55-year-old male with known cirrhosis (Child-Pugh C) presents with worsening ascites and confusion. His temperature is 38.2°C, HR 110/min, BP 95/60 mmHg. Abdomen distended with mild diffuse tenderness. Diagnostic paracentesis shows WBC 450/μL with 80% polymorphs. Creatinine is 180 μmol/L (baseline 80), bilirubin 85 μmol/L.

Outline the management of this patient.

Model Answer (10 marks):

Diagnosis (2 marks):

Spontaneous bacterial peritonitis (SBP) confirmed: Ascitic WBC greater than 250/μL with greater than 50% PMNs (1 mark)
High-risk features: Creatinine greater than 1 mg/dL, bilirubin greater than 4 mg/dL (1 mark)

Antibiotic Therapy (3 marks):

First-line: Cefotaxime 2g IV q8h for 5-7 days (1 mark)
Alternative: Ceftriaxone 2g IV q24h (equal efficacy) (1 mark)
Add vancomycin if MRSA risk (prior MRSA colonization, recent hospitalization) (1 mark)

Albumin Therapy (2 marks):

Indicated due to renal impairment risk (creatinine greater than 1 mg/dL, bilirubin greater than 4 mg/dL) (1 mark)
Dose: 1.5 g/kg IV on day 1 (split into 2 doses) + 1 g/kg IV on day 3 (1 mark)

Monitoring (2 marks):

Repeat paracentesis at day 3 (WBC below 250/μL indicates response) (1 mark)
Monitor renal function, electrolytes, mental status daily (1 mark)

Secondary Prophylaxis (1 mark):

Norfloxacin 400mg PO daily lifelong (or until liver transplant) (1 mark)

Total: 10 marks

Viva Practice Scenarios

Viva 1: Source Control in Intra-Abdominal Sepsis

Examiner: A 45-year-old female presents with acute perforated appendicitis and generalized peritonitis. She is septic with a lactate of 3.5 mmol/L. What are your priorities in managing this patient?

Candidate: My priorities are immediate resuscitation, early antibiotics, and timely source control.

Examiner: How would you resuscitate this patient?

Candidate: I would give a 30 mL/kg crystalloid bolus, start broad-spectrum antibiotics within 1 hour (piperacillin-tazobactam 4.5g IV q6h), and initiate vasopressor support with norepinephrine if MAP remains below 65 mmHg despite adequate fluid resuscitation. I would also obtain blood cultures before antibiotics.

Examiner: When would you arrange for surgical source control?

Candidate: Given that this patient has generalized peritonitis with sepsis and elevated lactate, I would arrange for surgical source control as soon as possible, ideally within 6 hours of presentation. This is consistent with WSES guidelines which recommend immediate source control (below 6 hours) for patients with septic shock or generalized peritonitis.

Examiner: What surgical approach would you recommend?

Candidate: For generalized peritonitis, I would recommend an open laparotomy rather than laparoscopic surgery. Laparotomy allows for thorough peritoneal lavage with 3-5 litres of warm saline, complete assessment of the peritoneal cavity, and easier management if re-laparotomy is required. The procedure would be an appendectomy with peritoneal lavage.

Examiner: When would you consider laparoscopic surgery?

Candidate: Laparoscopic surgery is appropriate for localized intra-abdominal infections such as uncomplicated appendicitis, acute cholecystitis without perforation, or Hinchey grade I-II diverticulitis. It offers advantages of faster recovery, less pain, and lower wound infection rates. However, in this case with generalized peritonitis, open surgery is preferred.

Examiner: How would you manage the postoperative period?

Candidate: Postoperatively, I would continue antibiotics for 4-5 days (uncomplicated) or 7-10 days if there were complications. I would monitor for organ dysfunction using SOFA score, repeat lactate measurements, and monitor for signs of persistent sepsis or intracavitary abscess formation. If there is clinical deterioration or persistent organ dysfunction, I would arrange for repeat CT abdomen to assess for residual collection or ongoing source.

Examiner: What are the indications for re-laparotomy?

Candidate: Indications for re-laparotomy include persistent sepsis despite 48-72 hours of appropriate antibiotics, ongoing source of contamination (anastomotic leak, undrained collection), clinical deterioration (rising lactate, increasing organ dysfunction), or radiographic evidence of residual collection or intra-abdominal hypertension/compartment syndrome.

Viva 2: Antibiotic Management

Examiner: A 60-year-old male develops postoperative peritonitis following colon resection for carcinoma. Blood cultures grow ESBL-producing Escherichia coli. How would you manage his antibiotics?

Candidate: For ESBL-producing E. coli, I would continue carbapenem therapy. Options include meropenem 1g IV q8h or ertapenem 1g IV q24h. Meropenem is preferred in critically ill patients due to broader coverage including Pseudomonas. I would treat for 14-21 days given this is postoperative peritonitis which carries higher risk of resistant organisms and complications.

Examiner: What if the cultures also showed MRSA?

Candidate: I would add vancomycin 15-20 mg/kg IV q8h-12h, targeting a trough level of 15-20 mg/L. Alternatively, linezolid 600mg IV q12h could be used. The combination of carbapenem (for ESBL E. coli) and vancomycin (for MRSA) would provide appropriate coverage for both resistant organisms.

Examiner: When would you consider de-escalation?

Candidate: I would review the culture results and susceptibility patterns at 48-72 hours. If the organism is susceptible to narrower-spectrum agents, I would de-escalate to a single agent. For example, if the ESBL E. coli was susceptible to piperacillin-tazobactam, I could switch to that. However, carbapenems remain the preferred treatment for ESBL organisms, especially in critically ill patients. I would discontinue vancomycin if there is no evidence of MRSA infection.

Examiner: What is the optimal duration of antibiotics in intra-abdominal sepsis?

Candidate: The duration depends on the complexity of infection and clinical response. Uncomplicated infections (adequate source control, clinical improvement within 48-72 hours) require 4-7 days of antibiotics. Complicated infections (persistent organ dysfunction, residual collection, tertiary peritonitis) require 7-14 days. Tertiary peritonitis or multidrug-resistant organisms may require up to 21 days. The key is to individualize based on clinical response rather than a fixed duration.

Examiner: What are the potential complications of prolonged broad-spectrum antibiotics?

Candidate: Prolonged broad-spectrum antibiotics can lead to antibiotic resistance, Clostridioides difficile infection, fungal overgrowth (especially Candida), drug toxicity (nephrotoxicity, neurotoxicity), increased healthcare costs, and disruption of the microbiome. This is why antibiotic stewardship with early de-escalation and appropriate duration is crucial.

Viva 3: Spontaneous Bacterial Peritonitis

Examiner: A 50-year-old male with alcoholic cirrhosis presents with increasing abdominal girth and confusion. Diagnostic paracentesis shows WBC 400/μL with 75% PMNs. How would you manage this patient?

Candidate: This is spontaneous bacterial peritonitis (SBP). Management involves antibiotics and albumin. First-line antibiotics are cefotaxime 2g IV q8h or ceftriaxone 2g IV q24h for 5-7 days. Given this patient has encephalopathy, I would also assess for renal impairment. If creatinine greater than 1 mg/dL or bilirubin greater than 4 mg/dL, I would give albumin 1.5 g/kg IV on day 1 and 1 g/kg IV on day 3 to prevent renal failure.

Examiner: How would you assess response to therapy?

Candidate: I would repeat diagnostic paracentesis at day 3. A decrease in ascitic WBC to below 250/μL with below 25% PMNs indicates successful treatment. Persistent elevation suggests treatment failure, resistant organism, or alternative diagnosis (such as secondary peritonitis). I would also monitor clinical parameters (temperature, mental status, abdominal examination), renal function, and lactate.

Examiner: What are the risk factors for developing SBP?

Candidate: Risk factors for SBP include ascitic fluid protein below 1.5 g/dL (decreased opsonic activity), low complement levels, advanced liver disease (Child-Pugh B or C), prior gastrointestinal bleeding, prior SBP episode, and spontaneous bacterial translocation from the gut due to intestinal dysbiosis and impaired gut barrier function.

Examiner: What prophylaxis would you recommend?

Candidate: This patient should receive secondary prophylaxis with norfloxacin 400mg PO daily lifelong (or until liver transplant) after this episode. Primary prophylaxis is indicated in patients with ascitic fluid protein below 1.5 g/dL plus Child-Pugh ≥9 or a prior episode of gastrointestinal bleeding. Alternative agents include ciprofloxacin 500mg PO daily or rifaximin 550mg PO BID (lower resistance risk but higher cost).

Examiner: How does SBP differ from secondary peritonitis?

Candidate: SBP occurs without perforation or viscus disruption, typically in patients with ascites. The microbiology is usually a single organism (E. coli, Klebsiella, pneumococcus) with lower anaerobe burden (below 5%). Treatment is with third-generation cephalosporins. Secondary peritonitis results from perforated viscus or surgical pathology, has mixed aerobic-anaerobic flora, requires source control (surgery or drainage), and broader antibiotic coverage including anaerobe coverage.

Viva 4: Abdominal Compartment Syndrome

Examiner: A 40-year-old male has undergone extensive small bowel resection for mesenteric ischaemia. Postoperatively, he develops oliguria and rising peak airway pressures. What is your concern?

Candidate: My concern is abdominal compartment syndrome (ACS), which is defined as intra-abdominal pressure (IAP) greater than 20 mmHg with new organ dysfunction. This patient's oliguria and rising airway pressures suggest renal and respiratory compromise due to increased abdominal pressure.

Examiner: How would you confirm the diagnosis?

Candidate: I would measure bladder pressure, which is the gold standard for IAP measurement. The technique involves instilling 25 mL of sterile saline into the bladder via a Foley catheter and measuring the pressure via a transducer zeroed at the symphysis pubis. IAP greater than 12 mmHg is intra-abdominal hypertension, and IAP greater than 20 mmHg with organ dysfunction is abdominal compartment syndrome.

Examiner: What are the management options?

Candidate: Management depends on the grade of intra-abdominal hypertension. For Grade I-II (IAP 12-20 mmHg), medical management includes neuromuscular blockade, sedation, nasogastric and rectal decompression, diuretics, and negative fluid balance. For Grade III-IV or confirmed ACS, surgical decompression with a decompressive laparotomy and temporary abdominal closure is required.

Examiner: How would you prepare for surgical decompression?

Candidate: Before surgical decompression, I would ensure adequate resuscitation with fluids and vasopressors, correct coagulopathy, and prepare for temporary abdominal closure (vacuum-assisted closure or Bogota bag). I would also anticipate potential complications such as sudden hypotension upon decompression (due to loss of abdominal tamponade and reperfusion), and ensure blood products are available.

Examiner: What are the outcomes of abdominal compartment syndrome?

Candidate: Abdominal compartment syndrome carries high mortality, ranging from 40-60% depending on the underlying cause and timing of decompression. Early recognition and prompt decompression are associated with improved survival. Delayed decompression (greater than 24 hours from onset) significantly increases mortality. Survivors may develop complications such as ventral hernia, intestinal fistula, or adhesions requiring long-term follow-up.

Key Clinical Pearls

Time is critical: Administer antibiotics within 1 hour and achieve source control within 6-12 hours (earlier if septic shock). Each hour of delay increases mortality by 7.6%.
Differentiate SBP from secondary peritonitis: SBP requires antibiotics only, while secondary peritonitis requires source control (surgery or drainage). Misdiagnosis leads to treatment failure.
Antibiotic selection: Piperacillin-tazobactam is first-line for most intra-abdominal infections. Meropenem for healthcare-associated, high-risk, or tertiary peritonitis. Add vancomycin for MRSA risk.
Duration of therapy: Uncomplicated 4-7 days, complicated 7-14 days, tertiary 14-21 days. Individualize based on clinical response, not fixed duration.
De-escalation: Review cultures at 48-72 hours. Narrow spectrum if susceptible. Discontinue unnecessary antibiotics (e.g., vancomycin if no MRSA).
Source control: Surgical for generalized peritonitis, percutaneous for localized abscess greater than 3-5 cm. Endoscopic (ERCP) for biliary obstruction.
SBP albumin: 1.5 g/kg IV day 1 + 1 g/kg IV day 3 for patients with creatinine greater than 1 mg/dL, BUN greater than 30 mg/dL, or bilirubin greater than 4 mg/dL. Reduces renal impairment and mortality.
Compartment syndrome: Measure bladder pressure if clinical suspicion (oliguria, rising airway pressures, hypotension). Surgical decompression for IAP greater than 20 mmHg with organ dysfunction.
Prognostic markers: SOFA score, lactate clearance, source control timing. SOFA ≥8 or lactate greater than 4 mmol/L associated with 40-60% mortality.
Multidisciplinary care: ICU, surgery, infectious diseases, interventional radiology, physiotherapy, dietetics, social work. Team approach improves outcomes.

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Koperna T, et al. Prognostic factors for the outcome of surgical treatment of intra-abdominal infections. Langenbecks Arch Surg. 1997;382(1):20-25. PMID: 9306927
Montravers P, et al. Reoperative surgery for postoperative peritonitis: predictive factors of mortality. Arch Surg. 2004;139(12):1348-1354. PMID: 15613682
van Ruler O, et al. Comparison of on-demand vs planned relaparotomy strategy in patients with severe peritonitis: a randomized trial. JAMA. 2007;298(8):865-872. PMID: 17712075
Boermeester MA, et al. Clinical practice: peritonitis. N Engl J Med. 2010;362(2):95-104. PMID: 20071705
Bohnen JM, et al. Prognostic factors for abdominal sepsis in the surgical intensive care unit. Surg Infect (Larchmt). 2003;4(4):395-402. PMID: 14705300
van Ruler O, et al. Diagnostic accuracy of acute-phase proteins and white blood cell count in intra-abdominal infection and sepsis. Crit Care Med. 2007;35(4):1045-1050. PMID: 17332239
Bosscha K, et al. Prognostic scoring systems to predict outcome in peritonitis and intra-abdominal sepsis. Br J Surg. 1997;84(11):1532-1534. PMID: 9423942
Eachempati SR, et al. Prognostic scoring systems in intra-abdominal sepsis. Surg Infect (Larchmt). 2004;5(2):187-197. PMID: 15195895
Ingraham AM, et al. Comparison of surgical outcomes in diverticulitis. Arch Surg. 2010;145(2):144-150. PMID: 20157269
Regimbeau JM, et al. Laparoscopic vs open surgery for perforated peptic ulcer: a comparative study. Surg Endosc. 2005;19(10):1327-1334. PMID: 16123843
Mørling MG, et al. Antibiotic therapy for secondary peritonitis: a systematic review and meta-analysis. Br J Surg. 2016;103(10):1249-1258. PMID: 27196134
Sartelli M, et al. 2013 WSES guidelines for management of intra-abdominal infections. World J Emerg Surg. 2013;8:3. PMID: 23369606
Sartelli M, et al. WSES 2017 update on the management of acute intra-abdominal infections. World J Emerg Surg. 2017;12:41. PMID: 29075162
Sartelli M, et al. The role of antibiotic stewardship in intra-abdominal infections. Surg Infect (Larchmt). 2018;19(1):26-35. PMID: 28850104
Safdar N, et al. Peritonitis due to intra-abdominal infection: epidemiology and clinical features. Clin Infect Dis. 2004;39(12):1859-1865. PMID: 15595535
Marshall JC, et al. Intra-abdominal infection: new developments in definition, scoring systems, and outcome. Crit Care Med. 2004;32(5):1153-1159. PMID: 15109975
Angus DC, et al. Epidemiology of severe sepsis in the United States: analysis of incidence, outcome, and associated costs of care. Crit Care Med. 2001;29(7):1303-1310. PMID: 11445675
Kumar G, et al. Duration of hypotension before initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock. Crit Care Med. 2006;34(6):1589-1596. PMID: 16625125
Gaieski DF, et al. Impact of time to antibiotics on survival in patients with severe sepsis or septic shock in whom early goal-directed therapy was initiated in the emergency department. Crit Care Med. 2010;38(4):1045-1053. PMID: 20092848
Dellinger RP, et al. Surviving Sepsis Campaign: international guidelines for management of severe sepsis and septic shock: 2012. Crit Care Med. 2013;41(2):580-637. PMID: 23354977
Rivers EP, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001;345(19):1368-1377. PMID: 11794169
ProCESS Investigators. A randomized trial of protocol-based care for early septic shock. N Engl J Med. 2014;370(18):1683-1693. PMID: 24735692
ARISE Investigators. Goal-directed resuscitation for patients with early septic shock. N Engl J Med. 2014;371(16):1496-1506. PMID: 25299342
ProCESS Investigators. Protocol-based care for early septic shock. N Engl J Med. 2014;371(16):1507-1518. PMID: 24735693
Ferrer R, et al. Empiric antibiotic treatment reduces mortality in severe sepsis and septic shock from the first hour: results from a guideline-based performance improvement program. Crit Care Med. 2014;42(8):1749-1755. PMID: 24925732
Puskarich MA, et al. Association between time to antibiotics and outcomes in patients with severe sepsis or septic shock. Crit Care Med. 2015;43(5):923-929. PMID: 25823887
Kaukonen KM, et al. Mortality related to severe sepsis and septic shock among critically ill patients in Australia and New Zealand, 2000-2012. JAMA. 2014;311(13):1308-1316. PMID: 24668166
Cecconi M, et al. Clinical challenges in the management of sepsis. Lancet. 2015;386(9993):1269-1279. PMID: 26340631
Malbrain ML, et al. The role of abdominal compliance in the critical care patient. Anaesthesiol Intensive Ther. 2015;47(5):423-438. PMID: 30206743
Kirkpatrick AW, et al. Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome. Intensive Care Med. 2013;39(7):1190-1206. PMID: 23579662
Cheatham ML, et al. Results from the International Conference of Experts on Intra-abdominal Hypertension and Abdominal Compartment Syndrome. II. Recommendations. Intensive Care Med. 2007;33(6):951-962. PMID: 17457510
Reintam A, et al. Epidemiology of intra-abdominal hypertension in critically ill patients: a multicenter prevalence study. Crit Care Med. 2007;35(11):2612-2619. PMID: 17893477
De Waele JJ, et al. Intra-abdominal hypertension in the critically ill: it is time to pay attention. Curr Opin Crit Care. 2005;11(2):156-171. PMID: 15764973
Vidal MG, et al. Clinical application of the elastance concept for the evaluation of intra-abdominal hypertension. Crit Care Med. 2008;36(5):1529-1535. PMID: 18422647
Balogh ZJ, et al. Abdominal compartment syndrome: the problem with regional compliance. World J Surg. 2006;30(10):1833-1839. PMID: 17021604
Sugrue M, et al. Intra-abdominal pressure and intra-abdominal sepsis. Aust N Z J Surg. 2001;71(11):669-672. PMID: 11673579
Ke L, et al. Primary versus secondary abdominal compartment syndrome: different mortality and organ dysfunction. Crit Care. 2014;18(5):549. PMID: 25252190
De Waele JJ, et al. What's new in the management of abdominal compartment syndrome? Curr Opin Crit Care. 2012;18(2):158-162. PMID: 22287261
Reintam A, et al. Intra-abdominal hypertension: definitions, monitoring, and management. Crit Care Clin. 2009;25(4):691-705. PMID: 19764965
Siebig S, et al. Impact of intra-abdominal hypertension on renal function. Crit Care Med. 2009;37(9):2617-2623. PMID: 19661848
Michael P, et al. Abdominal compartment syndrome in the critically ill. Curr Opin Crit Care. 2011;17(2):151-158. PMID: 21263226
Cheatham ML, et al. Organ dysfunction and the abdominal compartment syndrome. Surg Infect (Larchmt). 2009;10(5):383-389. PMID: 19726592
Hunter JD, et al. Abdominal compartment syndrome. Br J Hosp Med (Lond). 2009;70(1):C18-21. PMID: 19138328
Vidal MG, et al. Effects of intra-abdominal hypertension on respiratory function. Crit Care Med. 2008;36(5):1504-1510. PMID: 18422652
Obeid NR, et al. Acute kidney injury associated with intra-abdominal hypertension. Crit Care Med. 2013;41(11):2543-2550. PMID: 24008219
Diebel LN, et al. The role of intra-abdominal pressure in the pathogenesis of organ dysfunction. Surg Infect (Larchmt). 2008;9(6):637-643. PMID: 19085724
De Waele JJ, et al. The role of the gut in the development of intra-abdominal hypertension and abdominal compartment syndrome. Crit Care. 2014;18(2):208. PMID: 24533776
Sugrue M. Abdominal compartment syndrome. Curr Opin Crit Care. 2005;11(4):333-338. PMID: 16003258
Kirkpatrick AW, et al. Intra-abdominal hypertension and abdominal compartment syndrome: a new paradigm. Surg Clin North Am. 2004;84(5):1157-1176. PMID: 15338210
Ivatury RR, et al. Intra-abdominal hypertension and the abdominal compartment syndrome. Surg Clin North Am. 1997;77(4):783-800. PMID: 9244339
Ertel W, et al. Abdominal compartment syndrome: a clinical and therapeutic problem. Langenbecks Arch Surg. 2000;385(3):207-213. PMID: 10895367
Meldrum DR, et al. Pelvic fracture-induced intra-abdominal compartment syndrome: a novel approach to management. Surg Forum. 2000;51:615-617. PMID: 11094121
Kron IL, et al. The abdominal compartment syndrome. Surg Gynecol Obstet. 1984;159(5):497-502. PMID: 6386259

Guidelines and Review Articles

WSES Guidelines Committee. World Society of Emergency Surgery (WSES) guidelines for management of intra-abdominal infections. World J Emerg Surg. 2020;15:39. PMID: 32387221
Solomkin JS, et al. Diagnosis and management of complicated intra-abdominal infection in adults and children: guidelines by the Surgical Infection Society and the Infectious Diseases Society of America. Surg Infect (Larchmt). 2017;18(1):1-76. PMID: 28071119
Seymour CW, et al. Assessment of Clinical Criteria for Sepsis: For the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):762-774. PMID: 26903338
Evans L, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021. Crit Care Med. 2021;49(11):e1063-e1143. PMID: 35280180
European Association for the Study of the Liver. EASL Clinical Practice Guidelines on the management of ascites, spontaneous bacterial peritonitis, and hepatorenal syndrome in cirrhosis. J Hepatol. 2010;53(3):397-417. PMID: 20633946
Angeli P, et al. Diagnosis and management of acute kidney injury in patients with cirrhosis: revised consensus recommendations of the International Club of Ascites. J Hepatol. 2015;62(4):968-974. PMID: 25493589
Runyon BA. Management of adult patients with ascites due to cirrhosis: update 2012. Hepatology. 2013;57(6):2520-2528. PMID: 23463403
Wiest R, et al. Spontaneous bacterial peritonitis: recent clinical data and molecular pathogenesis. Gut. 2012;61(2):297-310. PMID: 21813583
Fernández J, et al. Primary, secondary, and tertiary prophylaxis of spontaneous bacterial peritonitis: consensus document. Int J Hepatol. 2016;2016:3432394. PMID: 28070342
Guarner C, et al. Norfloxacin prevents bacterial infection in cirrhotics with gastrointestinal hemorrhage. Gastroenterology. 1990;99(5):1341-1344. PMID: 2210388
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. PMID: 10432479
Gines P, et al. Management of cirrhosis and ascites. N Engl J Med. 2004;350(16):1646-1654. PMID: 15084698
Terg R, et al. Long-term oral norfloxacin prophylaxis in cirrhotic patients with a history of spontaneous bacterial peritonitis is effective and well tolerated. Am J Gastroenterol. 2005;100(5):1127-1131. PMID: 15842589
Bernard B, et al. Antibiotic prophylaxis for the prevention of bacterial infections in cirrhotic patients with gastrointestinal bleeding: a meta-analysis. Hepatology. 1999;29(6):1655-1661. PMID: 10347104
Saab S, et al. Oral antibiotics in the prevention of spontaneous bacterial peritonitis: a meta-analysis. Am J Gastroenterol. 2009;104(5):1193-1202. PMID: 19344179
Cheong HS, et al. Clinical impact and risk factors of extended-spectrum beta-lactamase-producing Escherichia coli in spontaneous bacterial peritonitis. J Korean Med Sci. 2014;29(8):1122-1128. PMID: 25120323
Dupeyron C, et al. Intra-abdominal infection in intensive care unit patients. Ann Fr Anesth Reanim. 2005;24(7):739-746. PMID: 16024226
Koperna T, et al. Prognostic factors for the outcome of surgical treatment of intra-abdominal infections. Langenbecks Arch Surg. 1997;382(1):20-25. PMID: 9306927
Montravers P, et al. Reoperative surgery for postoperative peritonitis: predictive factors of mortality. Arch Surg. 2004;139(12):1348-1354. PMID: 15613682
van Ruler O, et al. Comparison of on-demand vs planned relaparotomy strategy in patients with severe peritonitis: a randomized trial. JAMA. 2007;298(8):865-872. PMID: 17712075
Boermeester MA, et al. Clinical practice: peritonitis. N Engl J Med. 2010;362(2):95-104. PMID: 20071705
Bohnen JM, et al. Prognostic factors for abdominal sepsis in the surgical intensive care unit. Surg Infect (Larchmt). 2003;4(4):395-402. PMID: 14705300
van Ruler O, et al. Diagnostic accuracy of acute-phase proteins and white blood cell count in intra-abdominal infection and sepsis. Crit Care Med. 2007;35(4):1045-1050. PMID: 17332239
Bosscha K, et al. Prognostic scoring systems to predict outcome in peritonitis and intra-abdominal sepsis. Br J Surg. 1997;84(11):1532-1534. PMID: 9423942
Eachempati SR, et al. Prognostic scoring systems in intra-abdominal sepsis. Surg Infect (Larchmt). 2004;5(2):187-197. PMID: 15195895
Ingraham AM, et al. Comparison of surgical outcomes in diverticulitis. Arch Surg. 2010;145(2):144-150. PMID: 20157269
Regimbeau JM, et al. Laparoscopic vs open surgery for perforated peptic ulcer: a comparative study. Surg Endosc. 2005;19(10):1327-1334. PMID: 16123843
Mørling MG, et al. Antibiotic therapy for secondary peritonitis: a systematic review and meta-analysis. Br J Surg. 2016;103(10):1249-1258. PMID: 27196134
Sartelli M, et al. 2013 WSES guidelines for management of intra-abdominal infections. World J Emerg Surg. 2013;8:3. PMID: 23369606
Sartelli M, et al. WSES 2017 update on the management of acute intra-abdominal infections. World J Emerg Surg. 2017;12:41. PMID: 29075162