My 8yo GR has just been diagnosed with the above.  Any help appreciated on how to treat?
The more I read on the web, the more confused I get.

The search option doesn't show any posts regarding Anal Furunculosis, but if you search on Google 'Champdogs Furunculosis' there are a number of previous posts. Good luck.

I would start off with vets advice amd go from there .
Just noticed the willows who are well thought of have an article in it .Worth reading but your own vet would definitely be my start point and see how it goes from there
https://willows.uk.net/specialist-services/pet-health-information/veterinary-dermatology/anal-furunculosis/#:~:text=the%20local%20area.-,What%20is%20Anal%20Furunculosis%3F,other%20breeds%20can%20be%20affected.