Kidney, Ureter, and Bladder X-Ray Study
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 study is a preliminary screening test for kidney stones, and should be followed by a more sophisticated series of diagnostic tests [such as an abdominal ultrasound, intravenous urography, or computed tomography scan (CT scan)], if kidney stones are suspected.
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.
A KUB study requires no special diet, fluid restrictions, medications, or other preparation. The patient is typically required to wear a hospital gown or similar attire. A lead apron can not be used since it will obstruct necessary structures of the abdomen.
No special aftercare treatment or regimen is required for a KUB study.
The KUB study is an x-ray procedure, so it does involve minor exposure to radiation.
Normal KUB x-ray films show two kidneys of a similar size and shape, no renal calculi (stones), and a normal bowel gas pattern.
Abnormal KUB films may show calculi (kidney stones). If both kidneys are visible, it may be possible to diagnose renal size discrepancies. The film may also demonstrate an increase in bowel gas, indicating a possible bowel obstruction. In this case an additional film of the abdomen should be done either upright or in a lateral decubitus position. Soft tissue masses may also be visualized on a KUB.
Health care team roles
The x-ray technologist must confirm with the emergency physician that just a KUB is necessary to complete a diagnosis instead of a complete abdominal series. When a KUB is done with the mobile x-ray machine all staff remaining in the room must receive lead shielding. All radiographical technologists must be certified and registered with the A.S.R.T. and continue to upgrade and maintain their certification with ongoing education credits.
The x-ray technologist must advise the patient to remain still and follow breathing instructions so that a detailed image of the abdomen may be taken.
Pubic symphysis—The line of fusion between the pubic bones.
Ureteral stent—A surgical device implanted in patients with damaged ureters that holds the ureter open so that urine can flow freely from the kidneys to the bladder.
Meschan, Isadore. Radiographic Positioning and Related Anatomy. 3rd ed. Philadelphia: W.B. Saunders and Co.,1996.
Pagana, Kathleen Deska, and Timothy James Pagana. Mosby's Diagnostic and Laboratory Test Reference. 4th ed. St. Louis, MO: Mosby, 1998.
Lorraine K. Ehresman