Intra-Abdominal Infection & Peritonitis — Viva

Q1: Classification (2 min)

"How do you classify peritonitis, and why does the classification matter?" ^[1]

• By mechanism (the axis that decides treatment): ^[1]
  • PRIMARY (SBP) — infection of ascites WITHOUT an intra-abdominal source; cirrhosis/nephrotic; monomicrobial (E. coli, Klebsiella, pneumococcus); treated medically (cefotaxime + albumin); NO surgery.
  • SECONDARY — perforation or translocation from a hollow viscus; polymicrobial (Gram-negatives + anaerobes + Enterococcus); surgical emergency (broad-spectrum antibiotics + source control).
  • TERTIARY — persistent or recurrent infection despite source control in the critically ill; MDR organisms (Pseudomonas, Enterococcus/VRE, Candida, MRSA, Acinetobacter); re-operation + broadened cover + antifungal.
• By extent: generalised vs localised; by duration: acute vs chronic (TB, fungal); by route: contiguous, haematogenous, transmural.
• Why it matters: the classification dictates whether you treat medically (SBP) or surgically (secondary), and what organisms and antibiotics to expect.

Q2: The cirrhotic with fever (3 min)

"A 60-year-old cirrhotic with ascites presents with fever and confusion. Walk me through your management." ^[1]

• Diagnostic tap FIRST in every cirrhotic with ascites on admission or at any decompensation.
• Send ascitic fluid: cell count, Gram stain, culture (inoculate blood-culture bottles at the bedside for yield), protein, albumin (for SAAG), glucose, LDH.
• Diagnostic threshold: ascitic PMN over 250 cells per mm cubed = SBP — treat empirically before culture returns.
• Antibiotic: IV cefotaxime 2 g IV every 6 hours (the randomised-trial dose) (or ceftriaxone 2 g daily) for 5-7 days. ^[2]
• Adjunct: IV albumin 1.5 g per kg at diagnosis and 1 g per kg on day 3 — proven (Sort 1999 NEJM) to prevent renal impairment (33 to 10 percent) and reduce in-hospital mortality (29 to 10 percent) and 3-month mortality (41 to 22 percent). ^[1]
• Repeat tap at 48 hours: PMN should fallen to under half the baseline value; if not, suspect secondary peritonitis or resistant organism.
• Prophylaxis: secondary (indefinite norfloxacin 400 mg daily or ciprofloxacin 500 mg daily) because recurrence is 70% at 1 year; primary (low ascitic protein under 1.5 g per dL with impaired renal/hepatic function); GI bleed (7-day norfloxacin).
• Liver transplant referral — an episode of SBP is an indication.
• Distinguish from secondary: polymicrobial ascites (anaerobes), glucose under 50, LDH high, CEA over 5 = secondary — search for perforation with CT.

Q3: The acute surgical abdomen (3 min)

"A 50-year-old presents with sudden severe abdominal pain, board-like rigidity, absent bowel sounds and sepsis. Erect CXR shows free gas under the diaphragm. What is your management?" ^[1]

• Diagnosis: secondary generalised peritonitis from a perforated viscus (most commonly perforated duodenal ulcer; also perforated appendicitis, diverticulitis). ^[1]
• Resuscitation: ABCDE; oxygen; two large-bore cannulae; fluids (balanced crystalloid 30 mL per kg); analgesia (IV opioid titrated); nasogastric tube; urinary catheter; monitor.
• Antibiotics within 1 hour if septic shock: IV piperacillin-tazobactam 4.5 g every 6-8 hours (or ceftriaxone + metronidazole for community-acquired mild-moderate); add vancomycin/teicoplanin if MRSA risk; echinocandin if Candida risk.
• Blood cultures before antibiotics if possible (no delay).
• Source control: URGENT surgery — laparotomy (or laparoscopic) Graham omental patch for perforated duodenal ulcer; resection/anastomosis or Hartmann's for perforated diverticulitis; appendectomy for appendicitis.
• Do NOT delay surgery for extensive imaging in the unstable patient with a clear surgical abdomen and free gas.
• Post-op: ICU if septic shock; thromboprophylaxis; stop antibiotics once source control achieved and patient improving (about 4 days per STOP-IT).

Q4: Pitfalls and the high-yield numbers (2 min)

"What are the classic errors in managing peritonitis, and what are the numbers that decide the answer?" ^[1]

• Errors: missing SBP (no tap); delaying surgery for perforation; under-/over-resuscitation causing shock or abdominal compartment syndrome; failing to cover anaerobes/Enterococcus in healthcare-associated IAI; using oral quinolone for established SBP; not giving albumin; treating polymicrobial ascites as SBP. ^[1]
• Numbers:
  • Ascitic PMN over 250 = SBP.
  • Albumin 1.5 g per kg day 1, 1 g per kg day 3.
  • Cefotaxime 2 g every 6 hours (trial dose), shortened with clinical and ascitic monitoring.
  • Antibiotics within 1 hour in septic shock; 4 hours in stable.
  • About 4 days antibiotics post-source control (STOP-IT).
  • Abdominal compartment syndrome: bladder pressure over 20 mmHg + organ failure -> surgical decompression.
  • qSOFA 2 or more = high-risk sepsis.

References3ShowHide

1. [1]Sort P, Navasa M, Arroyo V, et al. Effect of intravenous albumin on renal impairment and mortality in patients with cirrhosis and spontaneous bacterial peritonitis N Engl J Med, 1999.PMID 10432325
2. [2]Rimola A, Salmerón JM, Clemente G, et al. Two different dosages of cefotaxime in the treatment of spontaneous bacterial peritonitis in cirrhosis Hepatology, 1995.PMID 7875666
3. [3]Ginés P, Rimola A, Planas R, et al. Norfloxacin prevents spontaneous bacterial peritonitis recurrence in cirrhosis Hepatology, 1990.PMID 2210673