Tattoo_mama, I once had a rat that got a tumour on her side too. It was so horrible... Poor thing... Luckily that's not what's wrong with this one.

Well, Min the rat seems a lot better tonight. I managed to find a rat specialist vet quite near to where we live and have borrowed some money off my parents so Min is booked in for an appointment tomorrow morning. I spoke to someone at the vet clinic and from what I described, it seems that Min has a respiratory tract infection, which should be treatable with antibiotics. I am hoping that maybe he won't need them though. Fingers crossed.