RT Journal Article SR Electronic T1 Biliary stones in the smooth hemispherical mass protruding into the duodenal lumen JF Frontline Gastroenterology JO Frontline Gastroenterol FD BMJ Publishing Group Ltd SP flgastro-2021-101835 DO 10.1136/flgastro-2021-101835 A1 Tsuyoshi Suda A1 Ryota Yoshida A1 Naoki Oishi A1 Eiki Matsushita YR 2021 UL http://fg.bmj.com/content/early/2021/04/07/flgastro-2021-101835.abstract AB