RT Journal Article SR Electronic T1 Hepatopulmonary syndromes JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP 1 OP 4 DO 10.1136/gut.46.1.1 VO 46 IS 1 A1 M J KROWKA YR 2000 UL http://gut.bmj.com/content/46/1/1.abstract AB