Would an emergency room in a hospital use a regular x ray to look for kidney stones before they would use a ct scan?

Plain X-rays of the abdomen and pelvis, usually called KUB (Kidneys, Ureter and Bladder), is no longer used for detecting kidney stone at the ER. If urinary stone is strongly suspected, CT stone protocol (no contrast) is the radiology test of choice initially.

Often kidney stones are not visible on a plain x-ray. A CT scan or other similar tests are often necessary. Good luck.