Billiary Drain anyone ?

Dx with stage 4 colon cancer with mets to liver a year ago,had colon resection by excellent surgeon, 6 months chemo and then 3 months maint. chemo after a clean PET scan, have had a billiay drain for about 9 month , a pain in my side to deal with daily, do they ever take these things out? what is the criteria (have had the drain replaced about 6 times over the months) if the tumors in my liver are gone, why do I need this troublesome drain ?