Intermitent Limp

Hello, one of my dog has a limp on her hind right leg that only occurs minutes after she gets up after lying down for a long period of time.
When she gets up her leg won’t touch the ground while standing up or walking.
In just a few minutes, she’ll touch the ground again, run, and jump with no sign of pain, but every time she gets up it’s the same thing, several times a day.
I’ve squeezed her leg all the way, and moved it around and she shows no pain or injuries,

I have a very special and painful case I need help with, I have tried several different veterinarians with no diagnosis or prognosis so far. It may be a long shot, but I was hoping you could help me shine a light on this.

In April I found an extremely skinny stray cat and took him in. I first thought he was malnourished from lack of food for being in the streets, but 4 months in his case keeps unfolding.

He is likely older than 15 years old, but he’s a happy cat with a lot of energy and mobility. He weighs 3kg but he’s a big cat, you can feel every single bone in his spine, although you can’t see them that easily because he has long hair. He’s completely affectionate, loves to be pet, and asks very politely for attention and food all the time.

All we know about his past is he is neutered, he had some teeth surgically removed and he tested negative for FIV and FeLV.

He had a huge appetite when I first took him in, he would eat 100g of food in one meal and ask for more right after. He would sometimes ‘cough’, it sounded like he was choking on some kind of fluid, it doesn’t happen in sequences, but it happens almost every day until today.

He always drank LOTS of water and produced a lot of urine as well. His feces at the beginning were really solid with some mucus.

After a month, he continued to eat plenty and hadn’t gained any weight, that’s when he started to throw up. It started happening a few days a week, usually after spending several hours without eating he would throw up a clear frothy fluid with no content, and then it progressed to twice every day regardless of when he had eaten.

We suspected it could be diabetes or hyperthyroidism, but the labwork didn’t confirm either, it showed regular kidney function with small liver function alterations.

We then introduced prednisolone (2,5mg/day) and changed his diet from a mix of natural home-cooked protein, hypercaloric wet food, protein supplements, and dry food to exclusively Royal Canin Hypoallergenic while waiting for Royal Canin Gastrointestinal Hydrolyzed Protein to arrive in Brazil, keeping Omega 3 (fish oil) 500mg/a day in his diet.

Vomits went away for a while. He kept drinking lots of water and peeing a lot, but his feces got softer (not liquid).

He had periods where he lost his appetite, which we treated with mirtazapine, he reacted after 6 days.

We performed an ultrasound and discovered that basically all his internal organs were compromised. He has severe alterations everywhere. Still, the best specialists I could find couldn’t tell me what was causing it and offer a course of treatment that didn’t involve opening him up to collect tissues for a biopsy.

I personally think it is absurd that a doctor could look at this frail elderly cat who obviously can’t resist anesthesia without serious risks and say that surgery is the only way to go, all to find out for sure if we’re dealing with a lymphoma or an infection. I’m looking for someone to advise me on the most effective course of action. Of course, I aim to reverse his condition, but I understand that given his age and how advanced it is, it might not be an option.

He is currently at 3kg, eating exclusively Royal Canin Gastrointestinal Hydrolyzed Protein with fish oil, and taking prednisolone every day for a month now. His appetite is healthy, he still drinks a lot, pees a lot, and poops regularly but softer. He eats an average of 5 small meals.
Vomits are back down to a few times a week, usually early in the morning before his first meal, and always a clear liquid. He goes and eats right after throwing up so I get the impression he is not nauseous.
He doesn’t seem to be in pain overall.
He’s not gaining any weight regardless of all my efforts.

That is why I’m giving this a shot and trying to get your attention. I hope you have more resources and knowledge that could help me figure out appropriate next steps to give this little guy the best fighting chances I can.

On this link you’ll find a translation of his bloodwork and ultrasound. I had chat GPT translate it for me so forgive me if there are errors.
Link: https://docs.google.com/document/d/1yqcen-TYzyvfBYU-J4t1tCHola1E2otDGDa1H7V032Y

I appreciate any support you can lend me, his name is Valentim which means brave and strong, and I want him to win this fight.