Teaching Case

A 2-year-old boy was admitted to our hospital with a one-month history of intermittent mild abdominal pain, hematochezia and mucus stool. Stool cultures were negative and blood tests revealed negative inflammatory markers, no transglutaminase or anti-gliadin antibodies and normal serum IgE potentially suggestive of cow milk or soy allergy.

The initial imagiological evaluation was made with an abdominal ultrasound (VF 10-5 MHz). The exam revealed an endoluminal polypoid structure with 20mm in diameter, soft tissue echogenicity and abundant central vascularization with colour Doppler (Fig. 1a, 1b and 1c). This structure was localized in the transverse colon, close to the hepatic angle, and multiple regional lymph nodes were enlarged. During the performance of the ultrasound, an invagination of 25mm segment of colon was seen, with the typical target sign, doughnut sign, or bull’s eye sign in the transverse view (Fig. 2a) and the pseudokidney sign in the longitudinal view (Fig. 2b), with the polypoid structure working as the lead point of the invagination (Video 1 and 2).

The intussusception reduced spontaneously during the examination.

A colonoscopy was performed and the origin of the polyp in the transverse colon was confirmed. The lesion was resected endoscopically (Fig. 3) and histopathology revealed an hamartomatous polyp (Fig. 4).

Intussusception is defined as the invagination of a portion of the proximal bowel and its mesentery (intussusceptum) into a contiguous segment of the distal bowel (intussuscipiens). Approximately 90% of intussusceptions are ileocolic, in which the ileum is invaginated into the colon, but ileoileocolic, ileoileal and colocolic can also occur. This condition is more common among children between 6 months and 2 years of age, [1] is a rare condition in newborns and is more common in boys than girls. [1, 2] Intussusception may present with the classic triad of acute abdominal pain, jelly bloody stools/hematochezia and a palpable mass, but can also cause vomiting, lethargy and other nonspecific symptoms. Intussusception it is an emergent condition that can lead to bowel obstruction, ischemia, perforation and peritonitis. [3]

In 90% of cases occurring in children, intussusception is idiopathic, although an association with hypertrophic lymph nodes acting as the lead point is noted in the course of gastrointestinal infection. In the other 10% of cases, a true pathologic lead point is present,  Meckel's diverticulum being the most frequent one, followed by duplication cysts, benign polyps and more rarely tumours or lymphomas, which are more common in neonates and older children and are usually self-limited. [1, 2, 4]

Ultrasound is highly accurate for the diagnosis of intussusception, with a sensitivity and specificity of almost 100%, and is frequently the first imaging method performed. Despite the classic radiologic signs described in the abdominal x-ray, like the meniscus and the coiled spring sign, plain radiograph has no place in the diagnosis of intussusception nowadays, and ultrasound is the first method of choice. [1]

Colocolic intussusception is extremely rare in children, is normally associated with polypoid structures and occurs more frequently outside the typical age range. [5] Some syndromes are associated with intestinal polyps, such as Peutz-Jeghers syndrome and inherited hamartomatous or adenomatous polyposis syndromes. In our case, there was only one polypoid structure and the absence of other clinical features or familiar history made this diagnosis less likely. [6]

The one-month history of intermittent mild abdominal pain and bloody stool of our patient reflected multiple intermittent and self-limited episodes of intussusception that were solved with the polyp resection.

Pathological lead points are detected by ultrasound in only one-third of patients. [4] In this case, the radiologist had a key role in the diagnosis of the intussusception responsible for the clinical presentation as well as the lead point, which was later confirmed by colonoscopy.

Informed written consent was obtained from the patient for publication.