A kidney, ureter, and bladder (KUB) X-ray may be performed to assess the abdominal area for causes of abdominal pain, or to assess the organs and structures. A kidney, ureter, and bladder (KUB) study is an X-ray study that allows your doctor to. KUB stands for kidney, ureter and bladder. An abdominal x-ray is an x-ray of the abdomen. No special preparation is needed. (Study type: X-ray, plain; related body system: Digestive and Urinary systems.