🩺 Chapter 79: Peritonitis

Primary (SBP) · Secondary (Perforation) · Tertiary · Peritoneal Dialysis-Related · Tuberculous · Antibiotics · Drainage

🩺 Peritonitis: Inflammation of the Peritoneal Cavity — A Surgical Emergency

📊 Classification
• Primary (SBP): haematogenous spread, no intra-abdominal source. Cirrhosis, nephrotic syndrome, post-necrotic ascites.
• Secondary: due to perforated viscus (appendicitis, diverticulitis, ulcer, trauma).
• Tertiary: persistent/recurrent after adequate therapy, often nosocomial pathogens.
• Peritoneal dialysis-related: from catheter contamination.
🦠 Microbiology — Primary (SBP)
• Monomicrobial (>90%)
• E. coli (40%), Klebsiella (7%), other GNB (20%)
• Streptococcus pneumoniae (15%), other Streptococcus (15%), Staph (3%)
• Gram-positive infections increasing
🦠 Microbiology — Secondary
• Depends on perforation level:
• Stomach: Lactobacillus, Candida
• Duodenum/proximal bowel: Bacteroides
• Colon: E. coli + Bacteroides fragilis (synergy)
📋 Diagnosis — SBP
• Ascitic fluid PMN >250 cells/mm³
• Culture positive
• pH <7.35, lactate >25 mg/dL
• Paracentesis: send for cell count, Gram stain, culture (inoculate blood culture bottles)
💊 Antibiotics — SBP
• 3rd gen cephalosporin (ceftriaxone/cefotaxime)
• Alternatives: ampicillin + aminoglycoside, piperacillin-tazobactam, meropenem
• Duration: 5 days (or longer based on response)
💊 Antibiotics — Secondary Peritonitis
• Aminoglycoside + clindamycin
• Or ceftriaxone + metronidazole
• Carbapenems or beta-lactam/beta-lactamase inhibitors for high-risk
• Surgical source control ESSENTIAL
📌 Key Pearls: SBP requires high index of suspicion in cirrhotic/nephrotic child with fever and abdominal pain. Paracentesis is diagnostic. Secondary peritonitis needs surgery — antibiotics alone fail without source control.

🩺 Step-by-Step: Peritonitis Management

1
Recognise peritonitis
Abdominal pain, tenderness, rebound, guarding, absent bowel sounds, fever, leucocytosis. Peritoneal signs indicate surgical abdomen until proven otherwise.
2
Initial resuscitation
IV fluids, broad-spectrum antibiotics, NG decompression. Surgical consultation immediately. Do not delay surgery for extensive imaging if peritonitis present.
3
Diagnostic paracentesis (if ascites present)
Send fluid for cell count, differential, Gram stain, culture (inoculate blood culture bottles), protein, glucose, LDH, pH.
4
Differentiate primary vs secondary
Primary: PMN >250/mm³, culture positive, no surgical source. Secondary: multiple organisms, high protein, low glucose, low pH, surgical source found.
5
Primary peritonitis (SBP) treatment
Ceftriaxone 50 mg/kg IV once daily or cefotaxime 50 mg/kg IV q8h. Duration 5-14 days. Consider albumin 1.5 g/kg at diagnosis (prevents renal failure).
6
Secondary peritonitis treatment
Surgical source control (appendectomy, perforation repair, abscess drainage). PLUS antibiotics: ceftriaxone + metronidazole OR piperacillin-tazobactam OR meropenem.
7
Peritoneal dialysis-related peritonitis
Cloudy effluent, abdominal pain. Gram stain often negative. Empiric intraperitoneal vancomycin + ceftazidime. Remove catheter if tunnel infection or refractory.
8
Tertiary peritonitis
Persistent infection after adequate treatment. Often Enterococcus, Candida, multidrug-resistant organisms. Antifungals (echinocandins), source control, supportive care.