Have allergy tests done!!! Food allergies can cause all those problems!!!
Dear Manish - sounds like the same thing my son has been suffering with for the last year and a half, after, his gallbladder was removed. He has had every test there is from three gastroenterlolgists - all of which came back, normal. He is convinced that he has a gallstone stuck in his bile duct - causing chronic nausea, weakness, headache etc.
Doctors will not do an ERCP because it is dangerous and the tests "don't warrant the surgery". That is medical lingo for "I don't want to be sewed". We have had very little help from all the specialists we have seen and no suggestions as to what it is. I've gotten more help from people here. Ask about a stone or 'sludge' in the bile duct next time she sees the doctor, and then, demand, a cure!
It's possible that it could be related to her surgery, however, it would be difficult to say that it is without having some testing done. The green colored liquid probably is bile, so it would appear that at least sproadically, she's refluxing bile into her stomach. Bile binding resins might help - the only way to know would be to try it. But if she's experiencing constipation it's going to make the situation worse.
If she's having bowel habit changes - in other words going from constipation to diarrhea - it would be more of an indication that she should probably have her biliary system checked out. Hopefully, she's following a low fat diet? Make sure that any meds she's taking for her arthritic condition aren't contributing to the stomach issues. Many people don't realize that many meds have very adverse effects on the GI system.
Bile does not accumulate in the intestinal system. Once it's released, it flows through the small and large intestine and can have a very irritating effect on the whole of the lower GI tract - typically causing diarrhea.
She might also want to talk to her doc about using something like carafate to coat her stomach from the caustic effects of the bile.