Ileus is a temporary and functional (non-mechanical) arrest of intestinal peristalsis , leading to impaired movement of bowel contents through the small and/or large intestine .
Distinguishing Point : Unlike mechanical obstruction, ileus has no physical blockage . The bowel appears patent but lacks the muscular contractions to move contents forward.
Types of Intestinal Obstruction
- Mechanical Obstruction
- Caused by a physical barrier in the intestine.
- Examples: Volvulus , incarcerated hernia , intussusception , tumors , impacted feces , foreign bodies .
- Non-Mechanical Obstruction (Ileus)
- Due to paralysis of intestinal musculature , not an anatomical blockage.
- Also called paralytic ileus or adynamic ileus .
- Most commonly seen postoperatively or due to intra-abdominal inflammation .
Etiology of Ileus
Common Causes
- Postoperative ileus : Most frequent, especially after abdominal or pelvic surgery.
- Peritonitis : Inflammation from infection (e.g., perforated viscus).
- Retroperitoneal pathology :
- Hematomas (e.g., ruptured AAA),
- Inflammation (e.g., pancreatitis, retrocecal appendicitis),
- Fractures (e.g., lumbar vertebrae).
Metabolic & Pharmacologic Causes
- Electrolyte Imbalances : Hypokalemia, hypomagnesemia.
- Drugs :
- Opioids (↓ GI motility via μ-receptors),
- Anticholinergics ,
- Calcium channel blockers (less common).
Other Contributing Conditions
- Renal failure
- Thoracic causes (e.g., pneumonia, myocardial infarction, lower rib fractures)
Postoperative GI Recovery Timelines
| GI Segment | Normal Function Return |
|---|---|
| Small Intestine | 0–24 hours |
| Stomach | 24–48 hours |
| Colon | 48–72 hours (most affected) |
Clinical Presentation
- Abdominal distention
- Nausea and vomiting
- Mild, vague abdominal discomfort
- Obstipation (no flatus or stool) or minimal watery stool
- Absent or hypoactive bowel sounds
- Non-tender abdomen (unless underlying inflammation)
Pain is typically non-colicky , which helps differentiate from mechanical obstruction.
Diagnosis
Clinical Evaluation
- History of recent surgery , trauma, infection, or medication use.
- Absence of bowel sounds on auscultation .
Imaging
- Abdominal X-ray :
- Dilated loops of bowel with air-fluid levels.
- Gas more prominent in the colon than in the small bowel (in postoperative ileus).
- CT Scan :
- Useful to rule out mechanical obstruction , abscess , or complication .
Contrast Studies
- Water-soluble contrast enema or oral contrast can help distinguish ileus from mechanical obstruction.
- In ileus, contrast may diffuse slowly through the bowel without a clear point of obstruction.
Management
Supportive Treatment
- NPO (nil per os): No oral intake.
- Nasogastric decompression : For vomiting or severe distention.
- IV fluids and electrolyte correction , especially potassium .
- Avoid opioids and anticholinergics (worsen motility).
- Minimal sedation to preserve gut activity.
Maintain serum K⁺ > 4.0 mmol/L for optimal gut motility.
Persistent or Complicated Ileus
- If symptoms persist > 5–7 days , suspect mechanical obstruction → Surgical consultation .
- Colonic pseudo-obstruction (Ogilvie’s syndrome) :
- Consider colonoscopic decompression .
- IV neostigmine (cholinesterase inhibitor) may be used; cardiac monitoring required due to risk of bradycardia.
High-Yield Notes
- Most common cause of ileus : Postoperative state
- Classic triad : Abdominal distention + Vomiting + Absent bowel sounds
- Initial step in management : Supportive care (NPO, fluids, NG tube)
- Key complication to rule out : Mechanical obstruction or peritonitis
- Ogilvie’s Syndrome = acute colonic pseudo-obstruction, often in elderly or immobile patients
