Funding

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

"Cochrane 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, Rigshospitalet, Copenhagen University Hospital, 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."