[Stones] After stone surgery-ultrasound

[mtjaffe at verizon.net]

Lucky had stone surgery about 6 weeks ago. Doing much better but still a tinge of blood in his urine even after 2 rounds of antibiotics.  Vet wants me to bring him in for an ultrasound and urinalysis next week.  Can anyone tell me what to expect from the ultrasound?  How are these done on piggies? Will he have to be anethesized?
Thanks,
Merle