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 91 OP 92 DO 10.1136/flgastro-2021-101835 VO 13 IS 1 A1 Tsuyoshi Suda A1 Ryota Yoshida A1 Naoki Oishi A1 Eiki Matsushita YR 2022 UL http://fg.bmj.com/content/13/1/91.abstract AB