It sounds like a reasonable initial workup was completed - including endoscopy. Other possible causes can include gallbladder or pancreatic disease.
You can consider an abdominal ultrasound to evaluate the liver and gallbladder, or a more specialised test like a HIDA scan with CCK stimulation can be considered.
To evaluate the pancreas, blood tests looking at the pancreatic enzymes as well as a CT scan can be considered.
These options can be discussed with your personal physician, or in conjunction with your GI referral.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
http://www.straightfromthedoc.com
Open to suggestions,
Angelsmiles2ca