I saw the "bulge" sign: Gastroduodenal artery aneurysm mimicking duodenal bulb submucosal tumor.

Gastroduodenal artery (GDA) aneurysms are rare vascular anomalies that can present with nonspecific symptoms, making diagnosis challenging. We report a case of a 26-year-old male presenting with abdominal distension, initially suspected to have a duodenal submucosal tumor. Advanced imaging techniques, including endoscopic ultrasonography (EUS) and computed tomography angiography (CTA), revealed a GDA aneurysm compressing the duodenal bulb. The patient was managed conservatively with regular follow-up, remaining asymptomatic over six months. This case underscores the importance of considering vascular anomalies in differential diagnoses of submucosal tumors and highlights the role of multimodal imaging in accurate diagnosis.