Can't say without examination.
Imaging the abdomen, and looking for problems in the liver and gallbladder can be considered. An ultrasound or CT scan would be a reasonable place to start.
Various types of upper GI conditions, including inflammation of the upper digestive tract, GERD, or an ulcer can be considered, and evaluated with an upper endoscopy.
These options can be discussed with your personal physician or gastroenterologist.
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.
www.kevinmd.com
www.twitter.com/kevinmd