Any ideas on what's wrong?

[Hiokami]

My dog has been throwing up since Monday night. We took her to the Veterinarian Wednesday morning.
Before we took her, she seemed to be eating normally and she was drinking lots of water.
The Veterinarian told us she could be dehydrated. He had blood tests done and nothing was found. He then took x-rays and saw something in her. He was supposed to take x-rays this morning again, but I haven't heard anything about them. My mother was informed that our dog threw up blood some time last night.

Any help on what this could be would be would be nice. Thanks.

[Whizzy]

It sounds like she might have some sort of blockage; either something in her stomach that's too big to pass, or something in her intestines.

There are several things that could be causing a blockage; she ate something that's not digestible, something got twisted, a tumor of some sort, just to name a few.

I hope your Veterinarian discovers what's wrong soon, and it's something that's easy to fix.