What Is The Purpose Of Flagyl After Having Jejunal Bypass Surgery?

I use Flagyl since my Jujunial bypass surgery in 1978, my doctor says she won t continue to prescribe because she doesn t see why I have to take it, I believe it has to do with periodic infection in the intestine. all I know is it relieves discomfort about every 2 to 3 weeks and I take Flagl ( or generic actually ) what do you know about this, Thanks