Summary
- Intussusception should be considered in young children with abdominal pain, particularly when clinical signs are non-specific or vague.
- Ultrasound has excellent diagnostic accuracy for intussusception and POCUS was not significantly different from radiology-performed ultrasound. It is a good “rule in” test in the ED.
- The “Inverted U” technique provides a systematic approach to scanning the abdomen and increases the likelihood of identifying ileocolic intussusception.
- Always confirm abnormal findings in two planes, measure transverse diameter, and use color Doppler to assess perfusion.
- Key ultrasound findings of intussusception:
“Target” or “doughnut” sign (>2.5–3 cm in diameter for ileocolic) — Transverse view
“Pseudokidney” or “sandwich” appearance — Longitudinal view
- Normal bowel differentiation:
Small bowel: smaller calibre, fluid-filled, peristalsis present
Large bowel: larger calibre, gas/stool-filled, haustral folds, minimal peristalsis
- Early identification and expedited management of intussusception via POCUS can reduce ED length of stay and improve outcomes.
It is important to visualize an intussusception in both planes to reduce the likelihood of mistaking it for thickened bowel loops, psoas muscle, stool, or other abdominal masses (Figure 11).
Small bowel intussusceptions can often be seen in the abdomen and in most cases are transient and do not require treatmentgenerally less than 2cm in diameter) and for the presence of peristalsis (absent in ileocolic intussusceptions) (Video 4).
Pathologic lead points may not be easily recognized with POCUS, therefore consider other imaging modalities when patients are outside the typical age range or with suggestive history or physical examination findings.
Ileocolic intussusception may self-reduce, therefore a positive POCUS examination with a subsequent negative radiologist-performed ultrasound is possible.
Figure 11: Inflamed, thickened bowel, not to be mistaken for intussusception
Video 4: Small bowel intussusception with the presence of peristalsis
What is NOT Normal?
Intussusception will appear differently due to the loss of air from the telescoped bowel. As a result, you are more easily able to visualize the intussusception compared to normal bowel. In the transverse view an intussusception appears as a “target” or “doughnut,” which is created by a hyperdense centre surrounded by multiple concentric hyperdense rings (Figure 6,8). This should have a minimum diameter of 2.5-3 cm with ileocolic intussusception. A “target” with a diameter of 2 cm or less suggests a small bowel intussusception, which generally self-resolve, and rarely require reduction. Intussusception appears as a “pseudokidney” or “sandwich” in the oblique or longitudinal view because of the multiple hypoechoic layers (Figure 10).
– The diameter of intussusceptions are typically estimated visually or “eye-balled.” However, if there is any uncertainty, callipers can be used to measure the anterior-posterior (AP) diameter from outer edge to outer edge in the transverse plane
In the case of a true ileocolic intussusception other findings can often be noted on ultrasound including small amounts of free fluid outside the intestine in the area of the intussusception as well as a small bowel obstruction. These findings are outside of the scope of this module and are discussed in the small bowel obstruction module.
Figure 6: Transverse image intussusception—Target or Doughnut sign
Figure 7: Transverse image intussusception, telescoping of the intussusceptum into the intussuscepiens
Figure 8: Transverse image intussusception—Target or Doughnut sign
Figure 9: Transverse image intussusception, telescoping of the intussusceptum into the intussuscepiens
Figure 10: Intussusception “pseudokidney” or “sandwich” in the oblique or longitudinal view
Video 3: Normal bowel transitioning into Intussusception
What is normal?
First it is important to identify the cecum in the right lower quadrant as the beginning of the large bowel. To identify the cecum first place the probe in the RLQ and identify the psoas muscle and iliac vessels in cross section [Figure 4]. Lateral to the psoas muscle the cecum can be identified as a gas or stool filled structure 5].
Figure 4: Transverse image of the RLQ, showing the iliac vessels in cross section and psoas muscle
Figure 5: Transverse image of the RLQ demonstrating a gas-filled cecum with posterior shadowing, positioned lateral to the psoas muscle.
Video 1: Transverse scan through the RLQ, displaying the gas filled cecum laterally and normal appearance of the terminal ileum with a smaller luminal caliber.
On ultrasound, distinguishing between small and large bowel can sometimes be challengingTypically, small bowel appears as having a smaller luminal caliber, contains fluid contents within, and demonstrates active peristalsis. Whereas large bowel has a larger calibre, is typically filled with gas or air and stool, has haustral folds and lacks peristalsis (Video 2).
Video 2: Normal large bowel, displaying haustral folds and lack of peristalsis
Intussusception occurs when one part of the bowel telescopes into another part of the bowel [figure 2]. 
Figure 2: An intussusception occurs when one part of the bowel telescopes into another
While intussusception can happen at any location along the bowel, ileocolic intussusception is the most common type of intussusception occurring in children requiring timely intervention to resolve and the focus of this module. This occurs where the ileum and cecum connect [figure 3].
Figure 3: Ileocolic intussusception is the most common intussusception in children and is the focus of this module. It occurs when the terminal ileum of the small bowel telescopes into the colon.
To look for an ileocolic intussusception the exam begins in the right lower quadrant of the abdomen and follows the course of the large bowel.
