Intestinal Obstruction

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Intestinal obstruction is a blockage of the normal flow of intestinal contents, which can be either mechanical (physical blockage) or functional (failure of peristalsis).

Aetiology

Intestinal obstruction can be classified based on cause:

  • Mechanical obstruction:
    • Small bowel: adhesions (most common), hernias, intussusception, volvulus, tumours.
    • Large bowel: colorectal cancer, diverticular strictures, volvulus (sigmoid or caecal).
  • Functional obstruction (paralytic ileus):
    • Postoperative ileus.
    • Electrolyte imbalances (e.g., hypokalaemia).
    • Peritonitis or intra-abdominal infections.
    • Drugs (e.g., opioids).

Pathophysiology

  • Obstruction leads to accumulation of gas and fluid proximal to the blockage.
  • Increased intraluminal pressure causes bowel wall distension and reduced blood supply.
  • Prolonged obstruction can lead to ischaemia, necrosis, and perforation.
  • Fluid shifts into the bowel lumen cause dehydration and electrolyte imbalances.

Risk factors

  • Previous abdominal surgery (adhesions).
  • History of colorectal cancer or polyps.
  • Hernias (risk of strangulation).
  • Chronic constipation (leading to faecal impaction).
  • Inflammatory bowel disease (strictures from Crohn’s disease).

Signs and symptoms

Symptoms:

  • Colicky abdominal pain (worse in mechanical obstruction).
  • Nausea and vomiting (early in small bowel, late in large bowel obstruction).
  • Abdominal distension.
  • Absolute constipation (no passage of stool or flatus in complete obstruction).

Signs:

  • Abdominal tenderness and distension.
  • High-pitched bowel sounds (early) or absent bowel sounds (late).
  • Signs of peritonitis if perforation has occurred (rebound tenderness, guarding).

Investigations

  • Blood tests:
    • Raised white cell count and CRP (suggests infection or perforation).
    • Electrolytes and renal function (to assess dehydration).
    • Lactate levels (raised in bowel ischaemia).
  • Imaging:
    • Abdominal X-ray: will show dilated loops of bowel with air-fluid levels.
    • CT abdomen (gold standard): identifies obstruction site, cause, and complications.
    • Contrast enema: used in large bowel obstruction to assess strictures.

Management

1. Initial Resuscitation:

  • Nil by mouth: to prevents further bowel distension.
  • IV fluids: to correct dehydration and electrolyte imbalances.
  • Nasogastric Tube (NG): for decompression in severe vomiting or distension.
  • Analgesia: avoid opioids if possible as they can worsen ileus.

2. Specific Management:

  • Mechanical obstruction:
    • Small bowel obstruction (SBO):
      • Adhesional obstruction: conservative management first (drip and suck approach).
      • Strangulated bowel: needs emergency surgery.
    • Large bowel obstruction (LBO):
      • Colorectal cancer: this requires surgical resection.
      • Sigmoid volvulus: endoscopic decompression with sigmoidoscopy.
  • Paralytic ileus: supportive management, electrolyte correction, and early mobilisation.

3. Surgical Intervention:

  • Exploratory laparotomy: performed for strangulated obstruction or ischaemic bowel.
  • Colonic stenting: considered for palliation in malignant obstruction.

Referral

  • Urgent surgical referral: if peritonitis, bowel ischaemia, or complete obstruction is suspected.
  • Gastroenterology referral: for strictures or inflammatory bowel disease-related obstruction.
GastroenterologymypanotesIntestinal Obstruction