Don't worry just because they didn't tell you anything. Your vet knows Killian better than they do, is familiar with him pretty much inside and out, so would be better equipped to come to any conclusion about the Ultrasound than they would.

Be glad that Ultrasounds exist - the old alternative might have been just opening him up to explore - and having had an MRI that was deafeninly loud to me, I can't imagine a doggie going through one of those!