Medical negligence case against private hospital for leaving biliary stent

My mother was diagnosed with gall bladder and cbd stones and were advised to undergo ERCP for CBD stone removal followed by laparoscopic gall bladder removal in 2016. They initially performed ERCP but said that we did not remove stone as there was infection inside (which they did not check prior). Again they performed ERCP, placed stent and said that stone has been removed now, afterwards they performed laparoscopy for gall bladder removal and my mother was discharged after recovery. The stent was removed 1 month after surgery as instructed. After 1 month the symptoms again came back and when we asked them they said that some stones are still inside. They again performed ERCP to remove it and stent was placed again. They told us that this stent has to be replaced after 6 months with another as there is stricture in CBD. As per their instruction after 6 months they replaced the stent with another ERCP. After 6 more months we visited them again for stent removal and they said it has been removed now and there are no issues. But after 4 months again symptoms appeared. When we visited another hospital they told us that stent is still inside. How can they leave it inside after claiming to remove it in reports. This has caused infection again in CBD and my mother has to go through another ERCP to remove it. We have gone through a lot of financial and mental distress because of all this. Kindly tell me if it can be filed as a case for medical negligence