Intussusception (summary)

This is a basic article for medical students and other non-radiologists

Intussusception occurs when a loop of bowel is pulled into the lumen of a distal bowel loop, and is an important cause of acute abdominal pain, particularly in young children.

Reference article

This is a summary article; read more in our article on intussusception.

Summary

• epidemiology
  • ​​vast majority of cases occur between the ages of 6 months and 3 years
• presentation
  • classical triad of colicky abdominal pain, vomiting and right upper quadrant mass
  • redcurrant jelly stool is a late sign, as blood and mucus in stool indicate bowel ischemia
• pathology
  • ​proximal bowel (called the intussusceptum) pulled into and pushed through distal bowel (called the intussuscipiens) by peristalsis
  • usually requires a lead point as a cause:
    • typically lymphoid tissue in children (which can be hypertrophied due to intercurrent illness)
    • often a polyp or tumor in adults
• radiology
  • ​​diagnosis in children often made by ultrasound, giving the target sign apperance of bowel within bowel
  • contrast enema may be used for diagnosis
  • often identified at CT in adults, which may also delineate the lead point
• treatment
  • ​air enema under fluoroscopy can often reduce intussusception in children, though will require surgical reduction if unsuccessful or if there are signs of ischemia
  • in adults, laparotomy is usually required, as the lead point often requires resection

Role of imaging

• identify intussusception
• identify the lead point
• provide image guidance for air enema reduction

Radiographic features

Plain radiograph

May show features of bowel obstruction, with dilated bowel proximal to the intussusception and collapsed bowel distally.

Fluoroscopy

Contrast enema will show the level of an intussusception as a mass protruding into the lumen and blocking retrograde contrast flow. Air enema may be effective at reducing the intussusception: air is insufflated under pressure to gently push the intussusceptum back out of the intussuscipiens.

Ultrasound

Sensitive examination for intussusception, particularly in children. Target sign or doughnut sign of bowel in bowel is the most striking finding ¹. May also identify lymph nodes or other lead point.

CT

Less commonly used in children but more common to identify adult intussusception on CT, where assessment of lead point can also be made, and assessment for metastatic disease in the case of a tumor acting as the lead point ².