Our little boy is sick

We are so sad. Our little boy was all of a sudden in A LOT of pain this afternoon. I had to call the on-call vet he was so bad. I brought him in and he had a high temperature. He was afraid to move and he was crying. I am so sad. I had to leave him at the vet overnight so they can monitor him. They will give him antibiotics and a special liquid thingy under his skin (instead of a drip - to hydrate him). We think he has some sort of infection in his bowel. There is always a possibility that he swallowed something like an elastic but we hope not. I hope he will be fine. The vet is going to call me later tonight to update me. This is the first time he has been away from his home overnight. The poor little guy. He must be so terrified. I can't stop thinking about him.