Regular xrays might show you a shadow, but we didn't find them particularly useful in Priscilla's case. Her xrays showed a shadow in an inoperable place but no other details. If it were us and we'd decided to spare our dog the chemo, we'd pass on the CT as an unnecessary expense. I'd think a bit about the endoscope/flush, though--although it's probably unlikely that there's something in there that can be flushed out, there's the off chance that he has a grass awn or some other foreign body up there that might be removable that way.
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."