How do you know if it's an ER visit or a regular vet visit? Lucky has been throwing up for two days now after trying to use the litter. I don't feel a hard stomach. He doesn't like his bottom touched at all. It's a mess of honestly I don't know what. There are two ER vets but it's going to be expensive and I honestly don't know if it's the right choice. I never dealt with this so I don't know if it's ok to wait a day.