I assume that by S.M.A. you are referring to superior mesenteric artery syndrome. This represents the obstruction of the duodenum where it is squeezed in the notch between the superior mesenteric artery and the aorta. I don't understand the "emergency" surgery as this syndrome presents with a slow progressive onset of symptoms and can frequently be precipitated by significant weight loss from other reasons. Ongoing inability to eat needs to be evaluated. Somtimes this is merely a delay in recovery of the stomach's ability to empty after being chronically obstructed. Other reasons need to be evaluated though. These could include ongoing H.Pylori infection, gastroparesis, celiac disease, stricture (scarring) of the connection that they made, etc. An upper GI series would be a typical first study to rule out gastric outlet obstruction. An upper endoscopy would also be appropriate as would a gastric emptying study. Another possibility is that the severe nutritional depletion alone has perpetuated the symptoms.
It sounds like you need some testing to figure out what is going on. A gastric emptying scan or an upper GI might be a good idea.