Look up both artery and vein thrombosis...........
Baby, one of the reasons the docs may be hesitating is that this condition has a high level of mortality, and that the operation may not be that easy to accomplish. Go to emedicine.com, sign in and read about superior mesenteric artery thrombosis. You need to understand all that's involved before you push for the surgery. Then, if he's willing to undertake the surgery, find a specialist in the field. This is an operation that should not be performed by those who are unfamiliar with the condition.
If you want help, you're going to have to push to get it. But you also need to understand the risks. In the meantime, ask about using TPN to get more nutrition, or another form of supplementary nutrition.