The hepatic fossa is divided into the pars hepatica that forms the hepatic cell cord and hepatic canal and the pars cystica that forms the gall bladder and bile duct, and the common bile duct develops from the common part during the embryonic period. Early separation of the hepatic fossa causes union failure and forms two bile ducts. In addition, the duct ostium opens into the stomach if the accessory bile duct is formed before the stomach and duodenum separate, and into the duodenum if the accessory bile duct is formed after the separation [21]. The drainage route is determined by the time lag between the separation of the stomach and duodenum, with the duodenum as the most common opening, followed by the stomach and pancreatic duct [21]. Goor and Ebert classified the morphological features of double bile ducts into four types in 1972 with double drainage to the duodenum [19]. In Japan, the classification by Saito et al., which is based on the Goor and Ebert classification, is generally used [20]. Duplicated bile ducts occur embryologically during nonunion of the hepatic diverticulum. The bile ducts run through the hepatoduodenal ligament and lesser omentum and open on the side of the lesser curvature when opening into the stomach [22].

To our knowledge, there has been only one reported case of repeated ulcers at the bile duct opening of the stomach [23]. In that case, the opening of the bile duct communicated with the common bile duct. Bile acid has been considered pathogenesis of gastric mucosal damage and ulceration for long time [24]. A high concentration of gastric bile acid has been recognized in patients with gastric ulcer but not in those with duodenal ulcer [25, 26]. Also, bile acid promotes gastric intestinal metaplasia, which is considered a precancerous lesion of gastric cancer [27, 28]. In fact, gastric cancer at an ectopic bile duct opening into the stomach has also been reported [12]. Therefore, exposure to bile acids from an ectopic bile duct opening can cause gastric mucosal damage, ulceration, intestinal metaplasia and cancer. In our case, we found a bile duct opening in the stomach that was similar to the papilla of the duodenum pathologically. Therefore, this appears to be the first case report of an ectopic bile duct concomitant with gastric ulcer hemorrhage. However, this patient had never experienced gastric ulcer and/or ulcer bleeding for more than 70 years until this episode. Just before the hematemesis and melena began, she had received treatment for herpes zoster on her trunk, and the related pain, stress, and medication may also have influenced formation of gastric ulcer.

During the operation, we found a thin cord connecting to the lesser curvature of the antrum from the hepatoduodenal ligament. However, we did not confirm whether the cord communicated with the bile duct because at that time, we did not know that an ectopic bile duct in the stomach could cause gastric ulcer and hemorrhage. After the operation, we found a variant bile duct originating from the left hepatic duct and proceeding to the stomach on magnetic resonance imaging, as was reported previously [18]. Understandably, we could not confirm communication of the variant bile duct into the stomach due to the patient’s post-gastric resection status.

In the present study, differential diagnoses of submucosal protuberances that cause gastric bleeding can include ectopic pancreas, double stomach, gastric hamartoma, hamartomatous inverted polyp, gastrointestinal stromal tumor, leiomyoma, glomus tumor, neuroendocrine tumor, hemangioma, lipoma, lymphangioma, and metastasis and invasion of malignant tumors in other organs. However, we ruled out these lesions by pathological examination. Hamartomatous inverted polyp was suspected due to the presence of ductal structures and smooth muscle tissue in the submucosa of stomach [29]. However, there was no cyst formation, and we ultimately ruled it out.

This study has some limitations. This is a retrospective study, and we did not confirm whether the cord at the dorsal wall communicated with the bile duct. In addition, the paraffin specimen block had already been discarded, and unfortunately, additional immunohistochemical staining could not be performed.