9 month old suddenly having bowel/stomach issues

Our 9 month mini poodle had vomited in his crate overnight, and we’ve had a few episodes of explosive and bloody diarrhea today. Not eating or drinking. Lethargic and shaky legs.

We saw a vet immediately and his x ray and blood tests all came back clear: no obstruction, negative for Parvo and pancreatitis. He was given fluids and is now sleeping. Vet gave us an Rx for metronidazole. Just waiting on a stool sample to come back tomorrow.

Anything else you’d suggest testing for? It seems like all the serious conditions have been ruled out but I am nervous. He is still not eating or drinking so we have contacted the vet.