It it possible for kidney stones to show up on ultrasound and not of ct scan if so what kind of stones would they be (uric acid)?

Rarely.: Virtually all stones can be visualized by ct scanning, except for the very rare indinavir stone. Prior to the widespread use of ct, stones that do not show up on x-ray films, like uric acid stones, were called radiolucent. Ct scanning is much more sensitive for the detection of stones than an ultrasound, and it is unlikely that stone visible on ultrasound is not seen on ct.

Right: You are right. Uric acid stones dont show up on xray, ct scan but on ultrasound only.

Uric acid stones: yes, this is possible: Uric acid stones are not very radio-opaque - so plain XRAY miss them; so might CT, unless contrast is used. Ultrasound will not miss them, unless small - less than 5 mm