She is emaciated. Dying of starvation. Any ideas?

Hello M:

I'm terribly sorry... But, surly the surgeon knew this would happen BEFORE her surgery, or knows how to stop it now. Call him.

excon

If I may ask why your dog had to have so much of her colon removed, disease related, obsruction?
Also, by colon do you mean the large intesine? Not implying that you are mistaken just trying to get an accurate picture.
And lastly what kind of dog is she?
Without getting into a lot of detail...
The small intestine is where the absorption of moisture and nutrients into the blood stream takes place,
Part of the colons' (large intestine) function is to remove moisture and electrolytes from the ingested material and then to form and store the stool until time to defacate.
You should touch base with your vet about these problems, she should be on a special diet, but if that diet is not working for her it needs to be reavaluated so that she can get the most from what she is eating.
Recommending dietary changes, I cannot do, the Veterianarian who knows her medical history is better for that.
Perhaps he/she could recommend a nutritional assesement by a reputable prescription diet manufacturer.
There are lots of prescription diets for all types of problems.
She may need dietary management along with supplements.
You could even get a second opinion if you feel so inclined, nothing wrong with two minds working on the same problem.
Good Luck
And check back, there are lots of dog people here more than willing to help.

Lady Sam is right. But, even a second opinion vet is going to want to know why that much colon ( AKA Large Intestine) was removed. If it was a malignancy, well, there may be still some elsewhere? Best have a good talk with the surgeon who did the surgery, before this goes on too much longer.