Cystic mass in close contact with the 1st part of the duodenum with an echogenic inner mucosal layer and hypoechoic outer muscular layer on ultrasound and a well-defined filling defect on barium meal, most consistent with a duodenal duplication cyst.

The ultrasound exam plays an important role:

• to suggest the diagnosis of a GIT duplication cyst by the combination of an echogenic inner mucosal layer and hypoechoic outer muscular layer

• to exclude other differential diagnoses at this age, such as omental cyst, and mesenteric cyst

The barium meal to exclude the possibility of an intraluminal duodenal diverticulum (see also the case: intraluminal duodenal diverticulum).