My cat (approximately 16 years old, short hair, no specific breed, indoor cat) has been vomiting pretty much every day (sometimes multiple times) for almost a month.
She had a scare with her kidneys about 2 years ago (elevated results of urea and creatinine) and has had blood tests regularly since, but her levels fell and have been good ever since.
Her brother passed away a few years ago from stomach cancer, and he showed similar symptoms in the beginning, but when we've taken her to the vets they've done X-ray and ultrasound and, other than a slight thickening of the stomach lining, couldn't see any lumps or anything out of the ordinary. She has also had blood tests and everything looks fine, very good kidney results, no sign of liver issues, no sign of diabetes.
She's been on antacids and laxatives from the vet (as much as we can get in her, she's not good with medications and gets very distressed) but they don't seem to be having any effect. When she's been in to the vets they sometimes give her an anti-nausea injection which stops her being ill for a few days, and then it starts up again. She's also had antibiotics, dewormer, B12 and a steroid injection at various times. Any improvement is only temporary for a few days and then she starts vomiting again.
She's a fussy eater and she gets dry food (Purina One, various flavours), tuna and white fish. Also, occasionally ham. She won't eat much else. She gets sick mostly in the morning and we suspected Bilious Vomiting Syndrome, but she already has food down through the day and gets other regular food throughout the day too, including late at night and that hasn't improved anything.
Most days she might be sick once (and it tends to be thick and dark brown, occasionally with food in or clumps of hair but mostly liquid), but sometimes it's two or three times. She's otherwise eating fine, drinking and urinating a normal amount and pooing regularly (not sure the laxative is making any difference).
The vets seem to be a bit stumped and just keep telling us to give her the laxatives / antacid, but there's obviously something else going on.
The only major change recently is that we were giving her a glycosamine and mineral supplement for arthritis, which we were mixing with milk to get her to take it as it was the only way to guarantee she'd take it all. We ran out of the first course a couple of weeks before she started getting sick and didn't get any more before she got ill, so it's been about six weeks since she had the supplement or any milk.
We're really worried but don't know what else to do. Everything is also complicated by the fact we're in the UK and the country is on lockdown because of the coronavirus, so while the vet is still open it's not easy to get an appointment.
We're waiting on a stronger antacid from the vets and we're going to try to give her exclusively white fish for a few days to see if diet is contributing (but it's the same diet she's been on for years).
Any ideas what it could be or what we could try next? The fact she seems to be in good health (particularly for her age) is what's confusing us as all the things we've seen that fit have a list of other symptoms that she just hasn't got.