B19. Types of ileus and their symptomatology.

Page created on October 18, 2021. Not updated since.

Definition and epidemiology

Ileus refers to the inability of intestinal contents to pass through the intestinal tract. We can distinguish multiple types according to the pathomechanism:

  • Mechanical ileus – due to a mechanical obstruction of the bowels
    • Obstructive ileus
    • Bowel strangulation
  • Dynamic ileus – due to functional impairment of peristalsis
    • Paralytic ileus
    • Spastic ileus

Obstructive ileus may be further classified as small bowel obstruction (SBO), large bowel obstruction, and gastric outlet obstruction. Mechanical ileus is an emergency as it may lead to strangulation, bowel perforation, and sepsis.

Because spastic ileus is so rare, most divide ileus into mechanical and paralytic types, ignoring spastic ileus completely.

Etiology and types

Obstructive ileus is the most common type. Obstruction may occur in the small bowel or large bowel. It may be caused by:

  • Luminal obstruction from the inside
    • Faecal impaction
    • Gallstone
    • Foreign body
    • Parasites
    • Certain foods (grapes, orange)
  • Bowel wall lesion
    • Strictures
      • Due to inflammation (due to Crohn disease, etc.)
      • Due to irradiation
    • Cancer
    • Polyp
  • Compression from the outside
    • Herniation
    • Adhesions

Adhesions are pathological fibrous strands of connective tissue between organs and tissues that are usually not connected. This is a common complication of abdominal surgery.

Bowel strangulation refers to the condition when the bowel is “strangulated”, which cuts of the blood supply of the affected bowel segment. This can occur due to bowel incarceration, volvulus, or intussusception. Bowel incarceration is a complication of hernia (topic B4). Volvulus refers to when a loop of bowel twists around the mesentery that supports it. Intussusception occurs when a segment of bowel folds into itself like a telescope. See the image here.

Paralytic ileus refers to ileus due to paralysis of the bowel wall muscles which drive peristalsis. This can occur due to a variety of reasons, most commonly due to:

  • Hypokalaemia and other electrolyte disturbances
  • Diabetes mellitus
  • Peritonitis
  • Abdominal surgery (postoperative ileus)
  • Anticholinergic or opioid drugs

Postoperative (paralytic) ileus is common and physiologic. It typically resolves spontaneously within 72 hours.

Spastic ileus refers to ileus due to spasm of bowel wall muscles. This is very rare, but may occur due to porphyria, uraemia, or heavy metal poisoning.

Clinical features

Patients may present acutely with colicky abdominal pain, vomiting, abdominal distension, and lack of passage of faeces and gas. Vomit may contain bile or faeces. Patients with ileus often develop hypovolaemia (due to vomiting and third-spacing of fluid).

Findings on auscultation are characteristic and important in forming a suspicion of ileus. They depend on the stage of development (early/late) and type of ileus.

Early phase Late phase
Mechanical ileus High-pitched, metallic-like bowel sounds Absent bowel sounds
Dynamic ileus Decreased bowel sounds Absent bowel sounds

Complicated ileus occurs if bowel is necrotic or perforated, in which case the patient may be very ill (septic) and peritonitic.

Diagnosis and evaluation

Patients should be evaluated for herniation and trauma. Digital rectal examination should be performed, as the rectum will be tight (collapsed) in case of mechanical ileus and loose in case of paralytic ileus. Blood per DRE may be a sign of strangulation or cancer.

Abdominal x-ray or CT should be performed and may show characteristic air-fluid levels in the bowels, bowel dilation proximal to the obstruction, and sometimes the point of mechanical obstruction itself.


Ileus should always be treated inpatient. The initial intervention is stabilisation. IV fluids are often necessary due to hypovolaemia, and any electrolyte disturbances should be treated. A nasogastric tube may be used to decompress the bowels. Prophylactic antibiotics should be used for complicated ileus.

Mechanical ileus requires surgery or endoscopy to treat the underlying cause. Complicated mechanical ileus requires emergency surgery, while uncomplicated ileus may only require timely surgery.

Dynamic ileus is not treated with surgery; instead, the underlying cause should be treated.


  • Bowel necrosis
  • Bowel perforation
  • Peritonitis
  • Hypovolaemic shock
  • Sepsis

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