An Anatomic Red Herring Found in the Diagnosis of Functional Vomiting

This report describes the case of a previously healthy 16-year-old patient who initially presented with emesis of unknown etiology that was refractory to standard medical interventions. The initial imaging revealed duodenum inversum, a rare anatomic abnormality that provided additional diagnostic complexity to this case. Though the final diagnosis was found to be functional vomiting, this case gives an instructive review of this rare anatomic abnormality, the significant effects it may cause, and how making a diagnosis of exclusion can be challenged by unusual turns in an otherwise straightforward presentation.