Mechanical Bowel Obstruction

Obstruction of the intestines which prevents the normal movement of the products of digestion

Aetiology

  • Adhesions or bands - congenital, from previous abdo surgery, from peritonitis
  • Incarcerated abdominal wall hernia
  • Volvulus
  • Tumour
  • Inflammatory strictures - Crohn’s disease, diverticular disease
  • Bolus obstruction - food bolus, faecal impaction (bed ridden, elderly, strong analgesics), impacted ‘gallstone ileus’, trichobezoar
  • Intussusception - usually initiated by mass in bowel wall e.g. tumour, enlarged lymphatic tissue

Clinical presentation

Symptoms

  • Symptoms indicate site of obstruction
  • Gastric outlet obstruction will present with vomiting of semi-digested food eaten a day or two previously (no bile)
  • Upper small bowel obstruction will present with vomiting large volumes of bile-stained fluid; presentation is acute (within hours of obstruction)
  • Distal small bowel/large bowel obstruction will present with colicky abdominal pain, distension, 'absolute' constipation and vomiting (possibly faeculent)
  • If bowel is only partially obstructed, clinical features may be less clearly defined

Signs

  • Dehydration
  • Abdominal distension
  • Visible peristalsis
  • Obstruction with tenderness may indicate bowel strangulation
  • Obstructing abdominal mass may be palpable
  • Centre of the abdomen will be resonant
  • Examine groins for an obstructing hernia

Investigations

  • AXR
  • CT - often performed after AXR to look for cause

Management

  • Nil by mouth, IV fluids and electrolytes
  • Pass a nasogastric tube to decompress stomach
  • Further management depends on cause

Complications

Bowel strangulation

  • Occurs when part of the intestine becomes trapped in an abnormal opening e.g. volvulus or intussusception
  • Venous return is obstructed → local intravascular pressure rises → arterial inflow compromised → infarction and perforation