Is a CT (Computed Tomography) scan recommended for diagnosing intussusception?

CT Scan for Diagnosing Intussusception

Ultrasound, not CT, is the preferred imaging modality for diagnosing intussusception in children due to its high diagnostic accuracy and lack of ionizing radiation exposure. 1

Primary Diagnostic Approach

Pediatric Patients (Most Common Population)

• Ultrasound is the first-line imaging modality for suspected intussusception in children, offering high diagnostic accuracy without radiation exposure 2, 1
• The American College of Radiology guidelines specifically note that ultrasound has proven useful in evaluating intussusception in the pediatric age group 2
• Ultrasound demonstrates the characteristic "target sign" or "bowel-within-bowel" configuration that is pathognomonic for intussusception 1, 3

When CT May Be Appropriate

CT should be reserved for specific clinical scenarios rather than routine diagnosis:

• Atypical or complicated presentations where the diagnosis is unclear and ultrasound is non-diagnostic 1, 3
• Prolonged symptoms (>48 hours) when assessing for bowel viability and complications before attempted reduction 4
• Adult patients where intussusception is rare and often has an underlying organic cause (tumor in ~65% of cases) requiring pre-operative evaluation 5
• Incidental finding during CT performed for other indications 6

CT Diagnostic Capabilities and Limitations

What CT Can Identify

• Bowel-within-bowel configuration with intraluminal mass showing alternating layers of high and low attenuation (target sign) 3, 5
• Mesenteric fat and vessels trapped between overlapping bowel layers 3, 5
• Vascular compromise indicators: severe engorgement or twisting of mesenteric vessels, loss of layered pattern, extraluminal fluid, bowel perforation 4, 5
• Bowel wall edema of the intussuscipiens and partial small-bowel obstruction, which correlate with non-reducible or difficult-to-reduce intussusception 4

Critical Pitfalls

• Transient small-bowel intussusceptions are frequently identified incidentally on CT in children and are usually of no clinical significance 6
• In one study, 25 pediatric patients had small-bowel intussusception on CT, but none required surgery; 10 of 14 patients with immediate repeat imaging showed spontaneous resolution 6
• The layered or target appearance can be mimicked by other processes, leading to false-positive diagnoses 3
• CT has limited ability to determine the primary disease causing intussusception, though it provides excellent pre-operative evaluation for tumor extension 5

Clinical Decision Algorithm

For suspected intussusception in children:

1. Start with ultrasound as the primary diagnostic tool 1
2. If ultrasound is negative but clinical suspicion remains high, consider CT or MRI as second-line imaging 7
3. Avoid routine CT due to radiation exposure in this young population 2

For prolonged intussusception (>48 hours):

1. If CT is performed and shows no bowel wall edema or obstruction, contrast enema reduction may be safely attempted 4
2. If CT demonstrates bowel wall edema or partial obstruction, expect difficult or non-reducible intussusception requiring surgical intervention 4

For adult patients:

1. CT is more commonly used as intussusception is rare and typically has an underlying pathologic lead point requiring identification 5
2. CT provides pre-operative staging if malignancy is suspected 5

Radiation Exposure Consideration

The ACR guidelines emphasize that CT involves radiation exposure and should be used judiciously in pediatric patients, with ultrasound or MRI being preferred alternatives when available 2, 7. This is particularly important given that most pediatric intussusceptions are ileocolic and readily diagnosed with ultrasound 1.