What will I really experience during the renal ultrasound?

Nothing. There are no symptosms that you will experience with a kidney ultrasound. This is an ultrasound test of the kidneys that is safe and does not emit radiation but is a very useful for examing the kidneys.
Generally nothing. The technician spreads a gel over the kidney area and uses a ultrasound probe , which generates high frequency sound waves , like a submarine sonar, to bounce of your kidneys and generate a picture.