Catheter probe endoscopic sonography is a relatively rapid and safe procedure, carried out during standard endoscopy, capable of distinguishing solid from cystic lesions and vascular from avascular masses. Herein we discuss the role of catheter probe endoscopic sonography in the emergency assessment of a patient with recent and severe bleeding from an ulcerated polyp, arising from the papilla. During the endoscopy, catheter probe endoscopic sonography showed the solid and submucosal nature of the lesion, suggesting its localised and benign nature and, most importantly, demonstrating the high risk of rebleeding from vascular structures communicating with the ulcer. Because of this finding three metallic endoclips were positioned. The lesion was not removed endoscopically because of its difficult position and the high risk of haemorrhage. The mass, removed through a duodenotomy, was shown to be a gangliocytic paraganglioma, an uncommon tumour, frequently resulting in surgery because of abdominal pain and gastrointestinal bleeding.