spasms of back leg and tail, all day

Question
My 12(ish) year old domestic calico cat is doing this odd thing with her back legs and tail. Her tail whips back and forth, stiff and twitching, and at the same time she pulls her back legs up one at a time, looks like marching in place. Seems involuntary, sort of like a spasm. Since this morning she has been doing it almost constantly when standing or walking.  

She is an indoor cat, had vaccinations up until a few years ago when she developed kidney problems, creatinine is just above normal. Sed rate is low, drinks and pees a lot. Had radiation for hyperthyroidism about a year ago.  Picky eater, always been very underweight. Had normal check up and full labs about 3 months ago.  Last BM today, looked normal, maybe slightly wider than usual.

In the past she has done this occasionally, as well as almost everytime when I am brushing her near her hind quarters.  But never nonstop for 8+ hours like this and for no apparent reason.  Should I be worried about this?

Answer
Sounds like she is having some nerve irritation on her lower back area. Some cats get a 'neuritis" in that area and it is very painful. The symptoms are the tail twitching, back twitching and some kicking but that is less common.

Most vets don't seem to understand this neuritis when I tell them about it so you have to just tell yours that you think that is what she has. It's hard to say what causes this as no one knows but the kidney problems could start it.

It is generally nerve related but if the kidneys are having some issues it could be radiated pain. I am not a vet so I can only give you suggestions as to what it possibly be.

I would certainly have your vet look her over or at least call him on Tuesday and discuss this with the technician or the vet.

This is something I wouldn't let go at her age. I hope that she is well soon.