Funding

All authors are kindly requested to add the following text under Acknowledgements:

"Cochrane Hepato-Biliary Review Group funding acknowledgement: 
The Danish State is the largest single funder of the Cochrane Hepato-Biliary Group through its investment in the Copenhagen Trial Unit, Centre for Clinical Intervention Research, the Capital Region, Rigshospitalet, Copenhagen, Denmark.
Disclaimer: the views and opinions expressed in this review are those of the authors and do not necessarily reflect those of the Danish State or the Copenhagen Trial Unit."