I agree with the testing that has been done, and indeed, many of the major causes of chronic nausea would have been ruled out with the imaging scans and upper endoscopy.
There are more specialized tests you can consider, including the ERCP with Sphincter of Oddi manometry that you had mentioned, as well as a 24-hr pH study looking for GERD and an esophageal motility test.
If the GI workup continues to be negative, there are a variety of neurological diseases that can lead to chronic nausea. If your doctor wants to pursue this route, head imaging with a CT scan or MRI can be considered.
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 Pho, M.D.
KevinMD.com
Twitter.com/kevinmd
I have had scans of every part of my body including my brain. Blood work to rule out adrenal gland problems. Endoscopies and Colonoscopy. I have not had the ERCP yet but that is planned. One doctor mentioned that he thinks that the "problem is on the 'molecular/ hormonal level' 'gut nerve or hormones'"