It's not too suprising that FU won't make any difference to outcome because we don't offer any effective treatment for recurrent disease (I'm assuming you are referring to hilar cholangios). This also probably explains the lack of definitive guidance regarding the manner and interval of follow-up. As far duration of FU, given that up to 80% of them recur within 5 years, then this would probably be appropriate for the minimum duration of FU. But as you quite rightly point out, there are no definitive guidelines.

But what about intrahepatic cholangios? If you had a local recurrence picked up early, would there be scope for further resection? I see your point about Klatskin tumours.

True, unfortunately there is litte data here as well in terms of the benefit of re-resection. There is a recent study by Pawlik in the Annals of Surgical Oncology suggesting a survival advantage to repeat resection. However, only 9% of patients were suitable. I think each case would have to be assessed on a "case by case" basis. In terms of a surveillance, we would normally default to a 6 monthly CT for two years and yearly after. But, this is no way evidence-based........

In terms of those unresectable, a study is under way: http://emcision-2204653.hs-sites.com/endobiliary-rfa-with-without-stenting ... some physicians are stenting when needed, some are performing RFA with stenting, which is what that study is comparing. Their frequency of follow-up varies. One example discussed at DDW 2016 was a woman with 4 years survival doing stenting and RFA every 6 months.