Investigation to know the cause and give direction
Since there is a history of removal of the gall bladder
after an attack of peritonitis
due to perforated gangrenous gall bladder with due preparations, I will think more of this as a cause of elevated bilirubin
After such an attack, the anatomy gets disturbed and the surgery difficulties and can cause some problems called as sequel such as narrowing of the bile passages and so on.
I would think of this as the first cause, another would be due to infection of the biliary tree( ducts), hepatitis
, some problem with pancreas
or occasionally drug induced.
The best way to diagnose is to have an MRI of the abdomen, to get the the tests of blood , particularly the liver function tests including alkaline phospatase.
Please post the reports if you have already undergone them.
Finding the reason will decide the direction of treatment, which includes medicines, therapeutic ERCP ( if you need to put a stent in the biliary ducts).
Hope this helps. Let me know if you need clarifications.