A Bowel Inside a Bowel: Intussusception

The Case

A 14 month-old female with no significant PMH who presented to the Emergency Department with vomiting. Per mom, patient was well yesterday, but today has been refusing food, crying and vomiting. Patient has had no known sick contacts and her vaccinations are up to date. A review of systems was performed and was otherwise negative.

Physical Exam

Vital signs were within normal limits. Patient was listless with decreased responsiveness, but not in distress. No evidence of respiratory compromise. Abdominal exam was unremarkable, with no focal tenderness and no guarding, rigidity or rebound. During the time the examiner was present in the room, the patient had one episode of crying inconsolably and then vomiting.

An abdominal ultrasound was performed and the diagnosis was revealed to be Intussusception

Ultrasound

Ultrasound has been shown to be 97.9% sensitive and 97.8% specific for diagnosing ileocolic intussusception. To evaluate for intussusception, start with the high frequency low penetration linear transducer. In most young children this transducer will provide adequate depth. In an older child, you may have to use the higher penetration curvilinear transducer. If available, use warm gel to minimize patient discomfort and thereby increasing your changes of obtaining clear images. Begin in the transverse plane and slide your probe up to the right upper quadrant, across, and then down the left side, interrogating for the intussusception (Figure 1).

Figure 1: Suggested path of the ultrasound transducer to evaluate for intussusception.  (https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/september-2018/pediatric-emergency-ultrasound-deep-dive-on-pocus-for-intussusception/)

Figure 1: Suggested path of the ultrasound transducer to evaluate for intussusception.

(https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/september-2018/pediatric-emergency-ultrasound-deep-dive-on-pocus-for-intussusception/)

Most of the intussusceptions will be found on the right hand side, and are described as a “target sign” when you are viewing the intestinal intussusception in transverse or the “sandwich sign” in long axis.  The “lawn-mower” approach can be used, similar to the approach for SBO, and graded compression along your path can help move bowel gas out of the way to better evaluate the intestine. The hyperechoic rings are the mucosa and muscularis and the hypoechoic portion is the submucosa.  

Case Discussion

Intussusception is the most common abdominal emergency in early childhood, with the majority of cases occurring in patients <2 years of age. It occurs when the bowel telescopes in on itself and gets stuck. The peristaltic waves of the bowel causes waves of pain in the patient. The classic triad is described as pain, vomiting and bloody stools. Ultrasonography is the preferred diagnostic modality to evaluate for intussusception, given the high sensitivity and specificity (97.9% and 97.8% respectively) when performed by a skilled clinician. Ultrasound also has a high negative predictive value (approaching 99.7%) and can rule out intussusception in a majority of patients. Intussusception presents on ultrasound as a peripheral hypoechoic ring surrounding a central echogenic focus described as either a "target sign” or a “doughnut sign.” (Figure 2a) The visualized doughnut represents the layers of the intestinal wall that have invaginated into themselves. Color doppler can be applied to evaluate for tissue ischemia. (Figure 2b) The most common type of intussusception, ileocolic (as in this case) is usually found in the right lower quadrant. There is usually associated focal tenderness in the right lower quadrant (though this patient was non-tender). Treatment of a non-perforated intussusception typically consists of reduction via air enema, but sometimes operative management is indicated.

Figure 2: Ultrasound image of intussusception

Figure 2: Ultrasound image of intussusception