Adynamic ileus

Adynamic ileus is the failure of passage of enteric contents through the small bowel and colon that are not mechanically obstructed; i.e. it represents a paralysis of intestinal motility.

Clinical presentation

Patients may be asymptomatic or present with symptoms similar to mechanical bowel obstruction such as nausea/vomiting, distension, and reduced or absent bowel movements. Bowel sounds may also be absent ¹². 

Pathology

Etiology

Adynamic ileus can be caused by several conditions:

• drugs, e.g. opioids
• metabolic, e.g. hyponatremia
• sepsis: especially gram-negative bacteria
• abdominal trauma or surgery (see below)
• myocardial infarction / congestive heart failure
• head injury or neurosurgery
• intra-abdominal inflammation and peritonitis
• retroperitoneal hematoma
• acute mesenteric ischemia: ileus limited to a vascular territory ¹⁰

The cause of ileus is thought to be complex and multifactorial, involving bowel inflammation ⁶, inhibitory neural reflexes ⁷, and neurohormonal peptides ⁸.

Postoperative ileus vs paralytic ileus

Some degree of ileus is a normal and expected finding after abdominal surgery, including C-section ⁹. Conventional recovery times have been reported as ⁴:

• small intestine: 0-24 hours 
• stomach: 24-48 hours
• colon: 48-72 hours

These intervals, however, may be overestimations ⁵.

Risk factors for postoperative ileus are: operative difficulty, operation more than 3 hours, bowel handling, drop in hematocrit levels, need of transfusion, increasing crystalloid administration, and lack of mobility after operation ¹².

Prolonged postoperative ileus (>72 hours) has been termed "paralytic" ileus by some and is concerning for small bowel obstruction, bowel perforation, peritonitis, and intra-abdominal abscess. 

Improving postoperative ileus is often determined clinically as much as radiographically, with the resumption of oral intake and flatus.

Radiographic features 

Plain radiograph

• generalized, uniform, gaseous distension of the large and small bowel
  • involvement of large bowel and lack of a transition point help distinguish it from small bowel obstruction
• when localized, there may be a sentinel loop

Treatment and prognosis

Improving gastric motility, boosting the nourishment status of the patient, and strengthening the stability of the interior environment are the main motives of therapy ¹¹.

History and etymology

"Ileus" ultimately derives from είλειν ("to twist"), which also gave rise to the section of the bowel termed the "ileum". At one time what we now call ileus had been called the "iliack passion" because it was believed that the intestines were twisted ³.