To answer your questions:
1) Fatty liver can be caused by alcohol, or associated with obesity and elevated triglycerides. If the liver enzymes are negative, this is less concerning.
2) An ALT of 21 suggests a mild case.
3) Serial monitoring of the liver enzymes is recommended.
4) It is normally a condition that comes on gradually.
5) If not associated with alcohol, it can be treated with weight loss and diet modification.
6) Yes, if it is not appropriate treated, the condition can worsen.
7) This is not an uncommon condition. I agree with the HIDA scan and upper GI series as additional tests.
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.
kevinmd_
http://www.mayoclinic.com/health/nonalcoholic-fatty-liver-disease/DS00577