10. Bowel obstruction (ileus)

Last updated on April 3, 2019 at 20:55

Introduction

Ileus is defined as a complete cessation of bowel passage. There is no passing of stool or gas. The partial form of ileus is called subileus.

Miserere, the vomiting of faecal matter, may occur. X-ray shows distended segments of the gut filled with fluid and gas. A splashing sound can be heard after pushing on the side of the abdomen.

The pathophysiology is complex and not fully understood. The lack of passage itself isn’t dangerous in itself, however it does induce significant stretch of the bowel wall. Bacterial degeneration of gut content leads to gas formation and even more wall stretch. This stretch evokes pathological reflexes that further inhibit gut motility. The stretch also impairs the circulation of the intestines, causing localized ischaemia with increased gut permeability. Necrosis, perforation and translocation of bacteria and toxins into the circulation may occur. Peritonitis is a possibility.

Another danger comes from salt, water, bicarbonate and potassium loss, causing exsiccosis, metabolic acidosis and hypokalaemia.

Three types of ileus exist:

  • Obstructive – where something mechanically obstructs the intestine
  • Dynamic – where there is no obstruction but also no motility
    • Paralytic – where there is no muscle activity
    • Spastic – where the muscle activity is uncoordinated and therefore inefficient

The obstructive and paralytic types are the most important.

Obstructive ileus

In obstructive ileus there is something that obstructs the intestinal lumen. Common causes include:

  • Tumors
  • Strangulated hernia
  • Volvulus
  • Invagination

The more proximal the obstruction, the worse the outcome. It’s treated by surgery. Bowel sounds can only be heard proximal to the obstruction.

Paralytic ileus

In paralytic ileus is there no muscle activity in the intestinal wall. There is no peristalsis and therefore no passage. Common causes include

  • Gastrointestinal surgery – also called postsurgical ileus
  • Hypokalaemia
  • Autonomic neuropathy
  • Non-occlusive mesenteric ischaemia
  • Peritonitis
  • Any irritation of the peritoneum
  • Obstructive ileus

Obstructive ileus causes activation of inhibitory nerve reflexes and hypokalaemia, both of which may be factors as to how obstructive ileus can progress into a paralytic one.

Non-occlusive mesenterial ischaemia may in severe cases cause paralytic ileus. It can occur due to heart failure, hypovolaemia or due to medications that vasoconstrict mesenteric arteries. The ischaemia damages the mucosa and may permit translocation of bacteria and digestive enzymes.

There are no bowel sounds in paralytic ileus.

Spastic ileus

In spastic ileus is there a continuous spasm of the intestinal muscles. The spasm has no coordinated activity and there is therefore no peristalsis. It may occur due to heavy metal poisoning or porphyria.


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9. Diarrhoea. Causes, pathophysiological forms, consequences

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11. Obstipation, subileus, diverticulosis. GIT motility disorders

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