She is coming round from the anaesthetic now. They have flushed her anal glands and taken samples for culture and sensitivity test to identify bacteria and which antibiotic is best to treat it.
The vet was suspicious that it may be a food allergy that's caused it?? Apparent most cats with food allergies start at around Ivy's age (news to me) so slow switch to a hypoallergenic food is recommended too.
My lovely neighbour (who is also a crazy cat lady) is going to pick her up for me. Lots of gentle snuggles required for my baby girl this afternoon!