A kidney, ureter, and bladder (KUB) x ray is an AP (anteroposterior) abdominal x ray. Despite its name, KUB does not show the ureters and only sometimes shows the kidneys and bladder and, even then, with uncertainty.
The KUB is used to detect kidney stones, foreign bodies in children, and to diagnose some gastrointestinal disorders. It is also used as a preliminary film for an intravenous pyelogram and barium enema, or as a follow-up x ray after the placement of devices such as ureteral stents and nasogastric or nasointestinal tubes (feeding tubes). It may also be requested in the operating room to detect sponges or clamps before the patient's incision is closed and would be done with the portable xray machine.
Because of the risks of radiation exposure to the fetus, pregnant women are advised to avoid this x-ray procedure.
A KUB is typically a single x-ray procedure. The patient lies supine (face-up) on the x-ray table and may flex the knees if it is more comfortable. The x-ray technologist centers on the iliac crest, making sure the pubic
symphysis will be visualized. The collimation may be reduced to the ASIS (anterior superior iliac spine) for better detail of the kidney outline, ureter and bladder, especially during an intravenous pyelogram.The radiographic technique of the film should demonstrate peritoneal fat lines, psoas muscles, and both renal (kidney) outlines. The patient is asked to hold his or her breath on expiration. Sometimes a second film is obtained with the patient standing.
Lorraine K. Ehresman, The Gale Group Inc., Gale, Detroit,