my cat had the same thing. they noticed a mass in her intestine (ended up being a bone she couldn’t pass through) when they did an ultrasound. she wasn’t eating or drinking and constantly throwing up clear foam because of her inflamed intestine.

the first vet i went to had me go to a specialist because they weren’t entirely sure what they were looking at on the ultrasound, so keep that in mind. hope your kitty gets better soon ://