Teaching Case

8-month-old male patient presented to the emergency room with acute abdominal pain and vomiting. He had no other significant signs or symptoms.

Abdominal ultrasound (Fig. 1), focused on the right iliac fossa (orange star indicating the liver), was performed which revealed the classical imaging findings of ileocolic intussusception:

Doughnut- or target-sign as transverse image showing sliding of the proximal bowel segment or intussusceptum (terminal ileum pointed with white arrow). Along with its hyperechoic mesenteric fat (blue arrow) into a distal bowel segment or intussuscipiens (transverse colon marked with yellow star).

Following the diagnosis, ultrasound-guided reduction by saline enema was attempted (Fig. 2). When saline enema (pink star) reached the intussusception, an inner cystic structure could be identified (green arrow) preventing the reduction to success. It was thought to be the cause of intussusception or leading point.

The patient underwent emergency surgery (Figs. 3 and 4), which confirmed ileocolic intussusception (white arrow). The surgical specimen revealed an endoluminal lesion (green arrow) that corresponded to a duplication cyst.

4.1. Background

Intussusception is one of the most common abdominal emergencies affecting children under 2-years-old.

It can involve any part of gastrointestinal tract, with ileocolic intussusception being the most frequently type producing clinical symptoms.

There is a wide range of aetiologies causing intussusception. Idiopathic or lymphoid hyperplasia is the main cause in children younger than 2 years, whereas pathological leading points are commonly seen in older children and adults. [1-3]

4.2. Clinical perspective

Since untreated intussusceptions results in bowel occlusion and ischaemia, eventually leading to bowel necrosis, perforation and peritonitis, an early diagnosis and treatment are essential.

The classical clinical triad consists of colic abdominal pain, palpable mass and bloody stool. Nowadays, symptoms such as vomiting, lethargy or paroxysms of pain or irritation are frequent.
Due to the overlap of symptoms with other causes of acute abdominal pain, clinical diagnosis can be challenging.

4.3. Imaging perspective

Ultrasound is the first-line modality of choice and a reliable screening tool for the diagnosis, especially in paediatrics population due to its lack of ionizing radiation.
It has a high degree of accuracy with a false-negative rate approaching zero.[4]

Peripancreatic collections, intestinal content in constipation, terminal ileitis and complicated appendicitis can simulate ileocolic intussusception on ultrasound, which is the reason for this false-positive diagnosis to be taken into account.

A specific finding that can help in the diagnosis is the presence of mesenteric adenopathies in the intussuscipiens lumen. This feature will differentiate ileocolic intussusceptions from ileoileal and other mimickers.

There is a wide spectrum of potential lead points that can cause secondary ileocolic intussusception (see differential diagnosis list).

4.4. Outcome

Ultrasound-guided reduction is an efficient and safe procedure that prevents exposure of young children to radiation with a good success rate. Ultrasound can also help in the characterisation of possible pathological lead points that otherwise with fluoroscopic guidance would be unnoticed. [2-4]

Both saline and air enema can be used as contrast material and have similar rates of success under ultrasound guidance. [4]

Nevertheless, it should be taken into consideration that ultrasound artefacts from air enema can prevent the identification of possible secondary causes of intussusception. [5]

Also, ultrasound-guided reduction using saline enema has the technical advantage that allows the identification of a real-time reduction with disappearance of the target-sign and solution reflux through the ileocaecal valve into the terminal ileum.

However, under fluoroscopic guidance air enema has a higher reduction success rate compared to saline enema. [6]

Other techniques without endoluminal contrast material as external manual reduction with ultrasound assistance have been described, but are still  researched due to its lack of use and the lack of knowledge about secondary effects. [7]

4.5. Teaching points

Ultrasound is both useful in intussusception diagnosis and guiding treatment, and can potentially help in the identification of pathological leading points.

Ileon duplication cysts are rare congenital malformations that can potentially cause ileocolic intussusception.

Written informed patient consent for publication has been obtained.