The scan is usually painless, but sometimes there is a little tenderness when the wand goes over certain areas, but I can't remember if there are any of those areas for a kidney ultrasound.

Usually the ultrasound tech will not tell you anything. They're not supposed to because they don't have the training to read the images. If the tech does tell you something, I would disregard it for that reason. The kidneys are very complicated organs.

Try to think of this process of diagnosis in stages, and try to focus on getting through this ultrasound, then getting the results before worrying about treatment and possible medication changes if you can

I'm glad your kitty is being so friendly