Risk Factors for Peri-operative Morbidity and Mortality in Perforation Peritonitis

1. Patient-Related (Host) Factors

2. Disease-Related Factors

3. Physiological Derangement at Presentation

• Respiratory failure: PaO₂ <8 kPa, FiO₂ >0.4, or mechanical ventilation >48 hours
• Acute renal failure
• Massive blood loss (>8 units)
• Electrolyte/metabolic derangement

4. Scoring Systems That Quantify Risk

• Mannheim Peritonitis Index (MPI) - incorporates age, gender, organ failure, duration of peritonitis, non-colonic origin, diffuse peritonitis, and degree of exudate
• POSSUM / P-POSSUM - physiological and operative severity score
• ACS NSQIP surgical risk score - validated pre-operative calculator
• APACHE II / SOFA - severity of sepsis/organ failure

5. Operative Factors

• Experience of the surgeon - particularly relevant in deciding between primary anastomosis vs. Hartmann's procedure in peritonitis
• Adequacy of peritoneal lavage and source control
• Anastomosis in contaminated field - risk of leak, especially with shock, immunosuppression, or poor tissue quality

Summary Mnemonic: "OLD CARTS" for risk stratification

• Old age
• Low albumin / nutritional status
• Delay in surgery
• Contamination (faecal > purulent)
• ASA class / comorbidities
• Renal impairment
• Toxic/septic shock
• Septicaemia / organ failure

Sources: Bailey & Love's Short Practice of Surgery 28th Ed., Table 21.6 (patient factors predisposing to high morbidity/mortality); Current Surgical Therapy 14e (diverticular perforation/peritonitis risk factors including NSQIP data).

Acute Mechanical Intestinal Obstruction

CAUSES [2 marks]

• Faecal impaction
• Foreign bodies
• Bezoars (phytobezoar, trichobezoar)
• Gallstone ileus (Bouveret's syndrome)

• Strictures - inflammatory (Crohn's disease, tuberculosis) or ischaemic
• Malignancy - carcinoma of the colon (commonest cause of large bowel obstruction)
• Intussusception
• Volvulus (sigmoid most common; caecal volvulus)
• Congenital atresia / stenosis (in neonates)

• Adhesions / bands - commonest cause of small bowel obstruction (post-operative)
• Hernia (obstructed/strangulated) - inguinal, femoral, umbilical, incisional, internal
• Compression by tumour, abscess, or haematoma

CLINICAL FEATURES [2 marks]

• Colicky, wave-like pain at regular intervals
• High jejunal obstruction: cramps every 3-5 minutes; referred to the epigastrium/umbilicus
• Terminal ileal obstruction: cramps every 8-10 minutes
• Large bowel obstruction: pain in the lower abdomen (hypogastrium)

• Frequent and early in high (proximal) obstruction
• Late and less frequent in distal/colonic obstruction
• Character: initially gastric contents → bilious → faeculant (a grave, late sign)

• Central distension = small bowel obstruction
• Peripheral distension = large bowel obstruction
• Regional distension = volvulus (sigmoid or caecum)
• Visible peristalsis may be seen (ladder pattern) - diagnostic

• Failure to pass both faeces AND flatus
• Takes at least 24 hours to develop; must not be relied upon as an early sign
• Note: diarrhoea can coexist (Richter's hernia, mesenteric vascular occlusion, pelvic abscess)

• More severe with proximal obstruction (massive fluid and electrolyte loss)
• Distal obstruction causes less dehydration but more distension

• Anxious, restless patient; early vital signs may be normal
• Inspect all hernial orifices (inguinal, femoral, umbilical) - a missed strangulated hernia is a common diagnostic error
• Borborygmi (high-pitched, tinkling) coincide with bouts of colic - diagnostic
• Muscle rigidity and rebound tenderness = strangulation/internal hernia - surgical emergency
• Silent abdomen = paralytic ileus or late strangulation
• Per rectal exam: ballooning of rectum in large bowel obstruction; occasionally palpable mass (intussusception, neoplasm)

DIAGNOSIS [2 marks]

• History and examination as above
• Key question: Is this simple obstruction or strangulation?

• Most important initial investigation
• Supine: gas-distended loops of bowel
  • Jejunum: valvulae conniventes - "concertina/stack-of-coins" appearance
  • Ileum: featureless straight-walled loops
  • Colon: haustral folds with indentations; gas-filled caecum in large bowel obstruction
• Erect: multiple air-fluid levels (step-ladder pattern)
  • More fluid levels = obstruction nearer the ileocaecal valve
• Sigmoid volvulus: "coffee bean" sign; caecal volvulus: kidney-shaped gas shadow

• Identifies the site, level, and cause of obstruction
• Detects strangulation, closed-loop obstruction, and perforation
• Increasingly the investigation of choice in uncertain cases

• Useful to confirm colonic obstruction site and delineate volvulus
• Barium should NOT be used if perforation is suspected

• FBC: leucocytosis suggests strangulation
• U&E: sodium and water depletion
• Serum creatinine, albumin
• Serum lactate: raised in mesenteric ischaemia/strangulation
• ABG: metabolic alkalosis (proximal obstruction with vomiting)

TREATMENT [4 marks]

A. Initial Resuscitation (All cases)

1. Nasogastric tube (NGT) decompression
   • Ryle's (non-vented) or Salem sump (vented) tube; placed on free drainage with 4-hourly aspiration or continuous suction
   • Reduces aspiration risk during anaesthesia; decompresses proximal bowel
2. IV fluid and electrolyte replacement
   • Hartmann's solution or normal saline (sodium and water are the primary deficits)
   • Guided by clinical assessment, urine output, and biochemistry
   • Urinary catheter for hourly urine output monitoring
3. Analgesia, NBM, baseline bloods, group and save
4. Antibiotics: Broad-spectrum IV antibiotics if strangulation suspected

B. Conservative Management (Selected cases)

• Adhesive small bowel obstruction without signs of strangulation: trial of conservative management for up to 72 hours
• Water-soluble contrast (Gastrografin) administration: both diagnostic and therapeutic in adhesive obstruction (has laxative effect, may resolve partial obstruction)

C. Surgical Treatment

• Obstructed or strangulated hernia
• Clinical features of intestinal strangulation (fever, tachycardia, peritonism, leucocytosis)
• Closed-loop obstruction
• Large bowel obstruction (rarely resolves spontaneously)
• Obstruction in a virgin (unopened) abdomen
• Failure of conservative management after 72 hours

1. Management of the segment at the site of obstruction
2. Decompression of the distended proximal bowel
3. Treatment of the underlying cause

• Midline laparotomy (if site unknown) for full exposure
• Identify: site of obstruction, nature of obstruction, viability of bowel
• Deliver distended small bowel gently into wound; cover with moist swabs
• Intra-operative decompression: orogastric tube with retrograde milking; or Savage's decompressor via purse-string
• Specific procedures by cause:

  Cause	Procedure
  Adhesions/bands	Enterolysis (division of adhesions)
  Obstructed hernia	Herniorrhaphy ± bowel resection
  Neoplasm (colon)	Resection ± primary anastomosis or Hartmann's
  Volvulus (sigmoid)	Detorsion; sigmoidectomy for recurrence
  Intussusception	Manual reduction; resection if non-viable
  Stricture/Crohn's	Stricturoplasty or resection

• Pink/red colour, normal sheen, peristalsis, mesenteric pulsation = viable
• If in doubt: wrap in hot packs for 10 minutes and reassess
• If still uncertain, resect - do NOT anastomose in unfavourable circumstances; bring out stomas instead

D. Post-operative Management

• Continue NGT drainage and IV fluids until bowel sounds return
• Early enteral feeding when tolerated
• Thromboprophylaxis, monitoring for complications (anastomotic leak, short bowel syndrome)

Sources: S Das - A Manual on Clinical Surgery 13th Ed. (pp.479-484); Bailey & Love's Short Practice of Surgery 28th Ed. (Ch. 78, Summary boxes 78.1, 78.11-78.13)