Liver inflammation

A liver biopsy 5 years ago indicated inflammation of the liver.  My doctor has done extensive testing, but no causes have been identified.  Since then, I have had my liver enzymes checked regularly.  Sometimes they are elevated, as in (138 - 183).  Sometimes they are normal (100 - 120).  A recent liver ultrasound showed everything normal.  What could cause chronic intermittent inflammation if I don't drink, don't have hepatitis, have not been poisoned (to my knowledge) and do not take offending medications?

[WaveRider]

"my liver enzymes checked regularly.  Sometimes they are elevated, as in (138 - 183).  Sometimes they are normal (100 - 120). "
What enzymes are these (SGPT, SGOT)? What are the ranges? An ultrasound will show if you material growing on your liver (cyst, tumor, cirrhosis) not determine its health. The gold standard still is a biopsy. Are you consulting with an Hepatologist, a liver specialist?