Internal Medicine


Occlusion or paralysis of the bowel preventing the forward passage of the intestinal contents, causing their accumulation proximal to the site of the blockage.


Mechanical ileus:


Mechanical obstruction of the gastrointestinal tract.

  • External compression (adhesions, hernia)

  • Changes in the bowel wall (tumour, inflammation/infection)

  • Blockage of the lumen (coprostasis, intussusception).


Postoperative ileus (POI):

Temporary cessation of coordinated bowel peristalsis after surgery, restricting the passage of bowel contents and rendering the patient unable to tolerate the oral intake of liquids or solid food.

Paralytic/functional ileus:

Failure of normal intestinal motility in the absence of mechanical obstruction.


  • Reflectory ileus—after abdominal or retroperitoneal surgery (e.g., spinal surgery), or induced by intra-abdominal or retroperitoneal lesions (tumor, hemorrhage, infection)

  • Drug-induced ileus—due to the consumption of opioids, neuroleptic drugs, etc.

  • Metabolic ileus—in patients with hypokalemia or diabetes mellitus

  • Vascular ileus—due to hypoperfusion of the bowel.



  • Adhesive disease (60%)
  • Neoplasm (20%)
  • Herniation (10%)
  • Inflammatory bowel disease (IBD) (5%)
  • Intussusception (< 5%)
  • Volvulus (< 5%)
  • Other (< 5 %)



Clinical features

Small-bowel ileus:

Presents acutely with severe symptoms.

  • Persistent and copious vomiting
  • Modest abdominal pain
  • Minimal abdominal distention

Large-bowel ileus:

Presents with mild symptoms (volvulus of sudden onset is an exception).

  • Significant abdominal distention and pain
  • Malodorous vomiting (uncommon)


  • Spontaneous perforation (3%)


Plain radiograph:


Axial computed tomography scan showing dilated, contrast-filled loops of bowel on the patient’s left (yellow arrows), with decompressed distal small bowel on the patient’s right (red arrows). The cause of obstruction, an incarcerated umbilical hernia, can also be seen (green arrow), with proximally dilated bowel entering the hernia and decompressed bowel exiting the hernia. | Jackson, P. G., & Raiji, M. T. (2011). Evaluation and management of intestinal obstruction. American family physician, 83(2), 159–165.

Exploratory laparotomy:

Abdominal computed tomography (CT) and intraoperative findings: (a) CT of a patient with mechanical small-bowel ileus, showing prestenotic dilatation of the small bowel (thick arrow), abrupt change of calibe, and a “hungry bowel” distal to the stenosis (thin arrows). (b) The corresponding intraoperative findings, with a dilated small bowel proximal to the area of previous stenosis (thick arrow); the adhesion (thin arrow), now divided, that caused the ileus; and the slowly recovering segment of small bowel, still hypoperfused because of the adhesion-related strangulation. | Vilz, T. O., Stoffels, B., Strassburg, C., Schild, H. H., & Kalff, J. C. (2017). Ileus in Adults. Deutsches Arzteblatt International, 114(29–30), 508–518.

Differential diagnosis

  • Ascites: Acute liver failure, history of hepatitis or alcoholism
  • Medications (e.g., tricyclic antidepressants, narcotics)
  • Mesenteric ischemia: History of peripheral vascular disease, hypercoagulable state, or postprandial abdominal angina; recent use of vasopressors
  • Perforated viscus/intra-abdominal sepsis: Fever, leukocytosis, acute abdomen, free air on imaging
  • Postoperative paralytic ileus (POI): Recent abdominal surgery with no postoperative flatus or bowel movement
  • Pseudo-obstruction (Ogilvie syndrome): Acutely dilated large intestine, history of intestinal dysmotility, diabetes mellitus, scleroderma


Conservative management (80%):

  • Nasogastric feeding:
    • IV fluid resuscitation (isotonic fluid)
    • Aggressive replacement of electrolytes
  • Antibiotics (treat intestinal overgrowth of bacteria and translocation across the bowel)

Surgical management:

  • Indications:
    • Strangulation, ischemia, complete absence of transit of bowel contents
    • Acute abdomen
    • Failure of medical management
Algorithm for evaluation and treatment of patients with suspected small bowel obstruction. | Jackson, P. G., & Raiji, M. T. (2011). Evaluation and management of intestinal obstruction. American family physician, 83(2), 159–165.

Postoperative ileus (POI) prophylaxis:

  • Minimally invasive surgery
  • Thoracic epidural catheter
  • Postoperative gum-chewing

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