A Scottish working group has raised the possibility of there being just one acute trust in Lothian, against the grain of government thinking.
The Scottish NHS white paper, Designed to Care, envisaged that trusts in all health boards would be cut, with one acute trust in each area.
However, it said for practical reasons this may not be possible in Lothian and Glasgow.
But the idea of one acute trust is among the options put forward by a working group set up to examine the reconfiguration of health services in Lothian.
The group is to consider two main options for reorganising services, which would cut Lothian's six trusts to two or three.
Under option one, the Royal Infirmary of Edinburgh, Western General Hospital, the Royal Hospital for Sick Children and St John's Hospital would be merged into a single acute trust.
In addition, there would be one primary care trust covering Edinburgh, East, Mid and West Lothian. It would incorporate mental health and learning disabilities services.
But the working group recognises the past success of the integrated hospital and community services model in West Lothian.
Under the second option, there would be one acute trust, combining the Royal Infirmary, the Western General and Royal Hospital for Sick Children, one primary care trust, covering Edinburgh, East and Mid Lothian, and one West Lothian integrated trust, including primary care services for West Lothian.
Consultation is expected to run from April to the end of June.