(Peri-Op Med & Anaesthesia) (Clinical Imaging)

Overview

• Bowel Obstruction → interruption of the normal passage of bowel contents through the bowel, either due to a functional or mechanical obstruction
• Functional Obstruction (Paralytic Ileus) → temporary disturbance of peristalsis
  • Common complication after surgery involving the bowel
• Mechanical Obstruction → due to a structural barrier (eg. tumour, adhesions), can be classified into SBO or LBO
  • Causes of SBO (80%) → adhesions (history of abdominal surgery) and incarcerated hernias. May also be due to gallstones (gallstone ileus).
  • Causes of LBO → malignant tumours (eg. colorectal carcinomas), diverticular disease (causes strictures), sigmoid/caecal volvulus
• Mechanical Bowel Obstruction vs Paralytic Ileus

Making Diagnosis

Clinical Features:

• Cardinal signs of mechanical bowel obstruction → colicky abdominal pain, vomiting, constipation, abdominal distension and decreased bowel sounds (may be tympanic/high pitched)

  • SBO ⇒ early onset bilious vomiting. Tinkling bowel sounds (more common in early bowel obstruction).
  • LBO ⇒ late onset vomiting. May also get absolute constipation (not passing wind and faeces). (May have hx of of possible malignant symptoms such as change in bowel habit, weight loss, rectal bleeding).

  <aside> 💡 Adhesions ⇒ won’t cause symptoms until months/years after surgery. Post-Operative Ileus ⇒ may occur sooner.

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• Paralytic ileus = complete absence of bowel sounds. Mechanical bowel obstruction = tinkling bowel sounds.

• SBO vs LBO

Investigations:

• CTAP with IV Contrast → gold standard diagnostic. Definitive investigation. Help establish cause.
• Erect AXR → 1st line as quick test if patient haemodynamically unstable. LBO = distended bowel around outside of abdomen, with haustra (don’t go all the way across, h = half). SBO = distended bowel in middle of abdomen, with valvulae conniventes (go all the way across).
  • Imaging Findings → 3-6-9 rule (SB-LB-Caecum). SBO leads to dilated loops which are predominantly central. LBO leads to dilated loops which are predominantly peripheral.
  • Small Bowel Obstruction AXR
  • Large Bowel Obstruction AXR
• Post-Operative Paralytic Ileus → monitor U&E’s (deranged electrolytes can contribute to development of postoperative ileus, hence important to check potassium, magnesium and phosphate)