请问什么是MRCP?并请帮看一下B超结果?多谢!

一年前因胆结石做了胆囊摘除手术,最近体检做B超,结果如下:
There is an echogenic shadowing structure, which appears to be in the common bile duct, measuring 11x8mm...

结论:
There is evidence of choledocholithiasis in this patient who has had prior cholecystectomy, Futher evaluation with a MRCP may be of benefit if clinically indicated.

想请问一下这个B超结果是说胆总管结石吗? 还是有别的可能才需要进一步做MRCP呢? MRCP对身体有没有辐射或者别的不好呢?

见医生还要等,很担心,先在这里问一下, 先谢谢了!