DESCRIPTION

• Intestinal obstruction is a blockage that keeps liquids, food, and other contents from passing through the small and large intestine.
  • May be partial or complete, constant or intermittent, mechanical or nonmechanical (functional)
  • May arise from intrinsic abnormalities (duodenal or intestinal atresia, duplication) or intraluminal (e.g., meconium ileus, meconium plug syndrome)
  • May arise from extrinsic factors (e.g., adhesions, bands, volvulus, or incarcerated hernia)
  • May also be caused by dysmotility of the gastrointestinal (GI) tract (i.e., hypomotility or paralysis of the intestine) secondary to a developmental disorder of the neuro enteric system (Hirschsprung disease) or more diffused neuromotor dysmotility (intestinal pseudoobstruction)
  • Most commonly involves the small bowel
• If untreated, obstruction can lead to intestinal ischemia and becomes a life-threatening situation.

EPIDEMIOLOGY

• Intestinal obstruction occurs in approximately 1 in 2,000 births.
• Intestinal obstruction accounts for >15% admissions for abdominal pain from the emergency department.

ETIOLOGY

May be congenital (e.g., atresia, duplication, malrotation), acquired (e.g., neoplastic, inflammatory), or iatrogenic (e.g., adhesions, radiation stricture); etiology varies by age:

• Neonates
  • Intestinal atresia (most common cause in neonates)
  • Obstructive meconium disorders (associated or not with cystic fibrosis)
    • Meconium ileus
    • Meconium plug syndrome
    • Meconium peritonitis
  • Duodenal atresia (high prevalence associated with Down syndrome)
  • Annular pancreas
  • Anorectal malformation/imperforate anus
  • Malrotation
  • Hirschsprung disease (Down syndrome)/small left colon (diabetic mothers)
• Infants
  • Pyloric stenosis (age: 1 to 2 months)
  • Intussusception (age: 2 months to 3 years)
  • Postoperative adhesions
  • Incarcerated inguinal hernia
  • Hirschsprung disease
  • Duplications
  • Meckel diverticulum
• Older children
  • Postoperative or postinfectious intestinal adhesions (e.g., perforated appendicitis)
  • Inflammatory bowel disease (IBD)
  • Malrotation with or without midgut volvulus
  • Annular pancreas
  • Meckel diverticulum
  • Superior mesenteric artery syndrome
  • Corrosive injury
  • Foreign body ingestion
  • Juvenile polyposis and related syndromes
  • Distal intestinal obstruction syndrome (cystic fibrosis)
  • Roundworm (Ascaris lumbricoides)
  • Gastric and intestinal bezoars
  • Colonic volvulus secondary to aerophagia and constipation (more common in neurodevelopmentally impaired)
  • Cancer-related intestinal obstruction and radiotherapy-induced adhesions

PATHOPHYSIOLOGY

• Pathophysiology depends on the mechanism of the obstruction.
• Mechanical obstruction
  • Intestinal dilation proximal to site of obstruction as the bowel fills with intestinal contents and air secondary to bacterial overgrowth proximal to the obstruction
  • Buildup of intestinal contents results in further distention, nausea, and vomiting.
  • Internal and external losses result in hypovolemia, oliguria, and azotemia.
  • Bacteria proliferate in the small bowel and its contents can become feculent.
  • “Closed loop” obstruction occurs when contents cannot get in or out of an intestinal segment.
• Ischemic obstruction
  • Occurs secondary to occlusion of intestinal blood supply
  • Causes
    • Twisting/kink of feeding blood vessels like in volvulus
    • Increased intramural pressure in the setting of bowel distention can result in decreased perfusion to the affected area.
    • Both occur in incarcerated hernia.
  • With progression, gangrene, peritonitis, and perforation may occur.
  • Damage to the normal gut barrier may enable bacteria, bacterial toxins, and inflammatory mediators to enter the circulation, causing sepsis.
• Functional obstruction (paralytic ileus)
  • Failure of intestinal motor function without mechanical obstruction
    • Congenital disorders like Hirschsprung disease and intestinal pseudoobstruction
    • Postoperative ileus
    • Other causes: infection (pneumonia, gastroenteritis, urinary tract infection, peritonitis, systemic sepsis), drugs (e.g., opiates, loperamide, vincristine), metabolic abnormalities (hypokalemia, hypomagnesemia, uremia, myxedema, and diabetic ketoacidosis)
    • Maternal substance abuse during pregnancy