Definition of Ileus
Ileus refers to the partial or complete blockage of the small and/or large intestine, which can be either functional (adynamic or paralytic ileus) or mechanical bowel obstruction. 1
Types of Ileus
Ileus can be categorized into two main types:
Functional (Adynamic or Paralytic) Ileus:
- Characterized by uncoordinated or attenuated intestinal muscle contractions without mechanical obstruction 2
- Results in diffuse gastrointestinal dysmotility
- Common after abdominal surgery, but can be exacerbated by numerous other conditions
Mechanical Ileus:
- Physical obstruction of the intestinal lumen
- Can be caused by adhesions, hernias, tumors, or other physical blockages
Clinical Manifestations
The clinical presentation of ileus typically includes:
- Abdominal distention
- Nausea and vomiting
- Accumulation of gas and fluids in the bowel
- Delayed passage of flatus and defecation 3
- Abdominal pain
- The severity and specific symptoms depend on the site of blockage 4
Pathophysiology
Ileus involves several pathophysiological mechanisms:
- Intestinal dilatation
- Increased luminal pressure
- Potential gut wall ischemia
- Increased intra-abdominal pressure (IAP)
- Abdominal fluid sequestration leading to systemic hypovolemia
- Intestinal bacterial overgrowth with potential bacterial translocation
- Inflammation of the intestinal wall with cytokine release 1
Historical Context
The term "ileus" has evolved significantly over time:
- Originally derived from the Greek word for "twisted" and was used to describe sigmoid volvulus
- Later used by Romans to describe various intestinal obstructions with similar symptoms
- During the Renaissance, it was synonymous with volvulus and intussusception
- In modern medicine, it has come to primarily refer to non-mechanical intestinal obstruction 5
Specific Types of Ileus
Postoperative Ileus
- Common after abdominal surgery
- Affects approximately 1.9-12% of patients after spine surgery 3
- Risk factors include intraoperative opioid use and excessive fluid administration
Opioid-Induced Ileus
- Results from activation of enteric μ-receptors
- Causes increased tonic non-propulsive contractions in small and large intestine
- Increases colonic fluid absorption and stool desiccation
- Increases minimum sensory threshold of rectum and anal sphincter tone 6
Colonic Pseudo-obstruction
- Presents with massive colonic dilatation with variable moderate small bowel dilatation
- Induced by metabolic disorders, motility-inhibiting drugs, severe illnesses, and extensive surgery 2
Complications
Serious complications of ileus include:
- Abdominal compartment syndrome (when IAP exceeds 20-25 mmHg)
- Multiple organ dysfunction affecting cardiovascular, hepatic, pulmonary, renal, and neurological function
- Severe systemic hypovolemia
- Systemic inflammatory response syndrome
- Invasive infections 1
Understanding the definition and pathophysiology of ileus is crucial for proper diagnosis and management, as it remains a common clinical concern that can lead to significant morbidity and mortality if not appropriately addressed.