I believe the general 'causes' of gastroparesis are considered to be: idiopathic, diabetes, scleroderma and other connective tissue diseases, (possibly) viral causes, due in some cases to fundoplication, it is found in some cases associated with neurologic disease states, in some cases of psychiatric 'states', and following the use of some medication.
In addition to what CalGal listed, you have also have post-viral GP, GP caused by a dysautonomia, caused by an eating disorder, caused by a mitochondrial disorder, and caused by an auto-immune disorder. Why do you and your doctor want to figure out what caused it? There usually isn't a reason to do this, and you can just be "labeled" as idiopathic gastroparesis.
My husband is belching often every day and night. He's been prescribed Prilosec, and I read that ginger in capsule form(550 mg.) 3 X a day is supposed to help with his digestive system. Also cardomom. Is this true?
He is experiencing some pain in the upper stomach. What do you recommend and advise him to do?
I advise that he see a physician. It is clearly affecting his and your life and deserves an answer. The Prilosec was given empirically. if it fails to relieve his symptoms further assessment is indicated.