I am really sorry Abigail has this problem, poor little girl it must be such a worry for you. Abigail doesn't sound overweight to me.
I am unable to offer you advice, however there are quite a lot of articles on the internet regarding this. I have found this one http://vetspecialists.co.uk/factshee...struction.html
If I were you I would print this off, take it to the vet and ask them to explain more clearly what they are going to do and what exactly is the problem. I would even ask them to write it down if you are unsure. I would also explore ways of managing this condition without surgery. If surgery is a must, is your vet the right person to do this?? or are their specialists that might be better suited?? especially as your vet seems to be working on a process of elimination, weight, possible heart problem both of which are negative.
Even so, try and work with your vet as you need his support to refer you if necessary.
Sorry I can't give you real advice but this is what I would do, research the condition, ask lots of questions and expect answers that you feel can understand and feel comfortable with.
Please let us know how you get on.
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