Treatment for superior mesenteric artery (SMA) Syndrome

After almost a year of tests, our 27 year old son has been diagnosed as, perhaps, having SMA Syndrome.  In the past 9 months he has lost 40 pounds, is in more pain, and gets weaker each month.  We would like to take him to a medical center that specializes in Gastroenterological problems for a second opinion and future treatment.  We live in central Texas but are willing to travel anywhere to get him help.

Can any of you recommend a medical center with experience in Gastrolenerology and diseases with SMA Syndrome symptoms?

Thank you for your consideration,
Kris's Mom