There are many benign causes of an isolated elevated bilirubin. An ultrasound would be a reasonable first step to determine if there is any over gall bladder disease.
It is also noted that the other liver enzymes are also negative - making it less likely it is a liver disease.
Other potential causes would include hemolysis (breakdown of red blood cells). This can be evaluated with several other tests such as reticulocyte count, anemia, and LDH level.
Medications can also elevated isolated bilirubin. Make sure that this is not a side effect of any medications you are taking.
If all the testing is negative, hereditary disorders such as Gilbert's Syndrome can be considered. This is a benign disease of bilirubin metabolism. No specific therapy is required for patients who are diagnosed with Gilbert's syndrome. The most important aspect of the care of these patients is recognition of the disorder and its inconsequential nature.
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.
Thanks,
Kevin, M.D.