Duodenum inversum: a rare cause of nausea and epigastric pain.

Duodenum inversum is a rare congenital anomaly of unknown aetiology characterised by the proximal duodenum travelling posteriorly and superiorly prior to crossing midline. Clinical presentations include epigastric pain, nausea, and abdominal distension. It can be associated with duodenitis, acute pancreatitis, peptic ulcer disease and functional biliary obstruction. In this case report, we discuss a 77-year-old male who presented with hematemesis and epigastric pain secondary to duodenitis, for which he had a CT scan of the abdomen which demonstrated duodenum inversum. Despite the rarity of the condition and its common omission from differential diagnoses, the ability to recognise duodenum inversum is important for radiologists, especially considering its implications in clinical management. If not diagnosed correctly, it may result in unnecessary hospital admissions, dietary restrictions, and perhaps even unnecessary surgery. In this case, the radiological diagnosis of duodenum inversum using CT allowed for conservative medical management and prevented surgical intervention.