The kidneys, ureters, bladder (KUB) radiograph is optimized for assessment of the urogenital system, and should not be confused with the AP supine abdomen view. However, in cases where the patient may have both gastrointestinal and urogenital abnormalities, all pathologies will still be reported.
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Indications
This view is useful in visualizing calcifications anywhere along the renal tract (i.e. kidneys, ureters, bladder, urethra). It is also used as baseline/interval images in contrast studies (i.e. intravenous urography).
Patient position
- the patient is supine, lying on their back, either on the x-ray table (preferred) or a trolley
- patients should be changed into a hospital gown, with radiopaque items removed (e.g. belts, zippers, buttons, ECG electrodes)
- the patient should be free from rotation; both shoulders and hips equidistant from the table/trolley
- the x-ray is taken on full inspiration
- this causes the diaphragm to contract, hence compressing the abdominal organs, allowing all renal contents to be visualized on a single image
Technical factors
- AP projection
-
centering point
- the midsagittal point (equidistant from each ASIS) at the level of the iliac crest
-
collimation
- laterally to the lateral abdominal wall
- superior to the upper kidney pole
- inferior to the inferior pubic rami
-
orientation
- portrait
-
detector size
- 35 cm x 43 cm
-
exposure
- 70-80 kVp
- 30-120 mAs; AEC should be used if available
-
SID
- 100 cm
-
grid
- yes
Image technical evaluation
- ensure visualization of the upper poles of both kidneys even if the diaphragm was not imaged
- the abdomen should be free from rotation with symmetry of the:
- ribs (superior)
- iliac crests (middle)
- obturator foramen (inferior)
Practical points
In male patients, it is acceptable to perform imaging with collimation extending inferior to the pubic symphysis as there may be renal calculi in the urethra too.
Exposure will need to be adjusted according to the imaging system (CR or DR) and patient size. Where possible, a higher kVp should be used in the evaluation of radiopaque objects.
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