For now, I have entered 'establishment' in the English-Catalan dictionary just as Jaume suggested.
In the Catalan-English dictionary, I have entered:
social class / social group<catexamp>L'estament militar</catexamp><engexamp>The military establishment</engexamp>
As regards 'estament mèdic', we need to come to a consensus on this expression before we add it to the dictionary.
"The medical establishment": the people controlling the medical profession (I think).
"L'estament mèdic": all the people working as a doctor. But often disapproving just like in establishment.
I agree with Jaume, 'the medical establishment' does indeed suggest the people controlling the medical profession.
'Medical profession' means all the people working as doctors but I don't believe the expression could ever be considered to be disapproving in English. I'm not sure if there is such an expression...