They can run titers to see if there is lepto exposure, r0bb53. It appears to be endemic in our area and we get recurring cases, but all have been mild. We notice the symptoms and treat it early.
We've never had lepto manifest with the symptoms your dog is having, but that might be just because we've been fortunate to catch it quickly.
It sounds more to me like a blockage of some sort--and as Rgeurts says, xrays can be pretty useless for blockages or partial blockages.
If he's not keeping water down, he's likely going to need fluids for dehydration, so I'm glad you're keeping in touch with the vet hospital. I hope you get some answers about Timber's condition soon!