Table 1. Summary of the Studies Used in Meta-Analysis.

Study	Design	Location	Setting	Time period	No. of liver transplant patients	No. of endoscopic retrograde cholangiopancreatography	Study quality
							Selection	Comparability	Outcome/exposure
Husing et al [5]	Retrospective analysis	Germany	Population based	1998 - 2013	157	454	***	**	**
Ambrus et al [12]	Retrospective analysis	Denmark	Population based	2003 - 2012	127	292	****	*	***
Law et al [13]	Retrospective analysis	USA, Spain	Population based	2000 - 2011, 2003 - 2012	301	730	****	**	***
Sanna et al [14]	Retrospective cohort study	Italy	Population based	1990 - 2007	94	150	****	*	**
Balderramo et al [15]	Retrospective analysis	Spain	Population based	2003 - 2010	121	243	**	*	**
Pievsky et al [16]	Retrospective analysis	USA	Population based	1997 - 2012	120	219	****	*	**
Singh et al [17]	Retrospective review	USA	Population based	2005 - 2011	71	159	****	*	**
Brown et al [18]	Retrospective review	USA	Population based	2013 - 2017	98	98	****	**	*
Abu Rajab et al [19]	Retrospective review	USA	Population based	2000 - 2007	146	146	***	**	***
Singh [20]	Retrospective review	USA	Population based	2005 - 2015	109	235	***	**	***
Li et al [21]	Retrospective review	China	Population based	2015 - 2018	48	48	****	**	**
Faleschini et al [22]	Retrospective analysis	Italy	Population based	2000 - 2012	142	490	****	**	**
Ramesh et al [23]	Retrospective review	USA	Population based	2002 - 2013	210	210	***	**	***
Catron et al [24]	Retrospective Review	USA	Population based	2017 - 2018	43	66	***	**	***

“*”, “**”, “***” and “****”: Newcastle-Ottawa Scale Star system representing the score given by authors to included studies judged on three broad perspectives: the selection of the study groups; the comparability of the groups; and the ascertainment of either the exposure or outcome of interest for case-control or cohort studies, respectively.