Computed Tomography of Kidneys, Ureters and Bladder (CT KUB)

By Dr. Damien Jonas Wilson, MDReviewed by Dr. Liji Thomas, MD

A computerized tomography (CT) scan of the kidneys, ureters and bladder (KUB) is referred to as a CT KUB.

The purpose of the scan is to obtain images from different angles of the urinary system and surrounding structures, which encompasses the area from the superior poles of the kidneys down to the pubic symphysis.

These images are acquired in cross-sections or slices, hence the terminology ‘tomography’.

They are then processed through a computer to produce three-dimensional pictures in vertical series which provides important and voluminous data as a means of identifying pathologies in the area examined.

Indications

Acute undiagnosed abdominopelvic pain without a clear etiology, and accompanied by symptoms such as nausea, vomiting, diarrhea and/or issues with passing urine, is the primary indication for a CT KUB. Many conditions may be associated with signs and symptoms in this region.

These include, but are not limited to, intestinal blockage, gall or urinary bladder stones, malignancies, and complications of inflammation and/ or infection.

Where applicable, a contrast agent may be used to obtain a detailed outline of the urinary system to detect anatomical abnormalities.

What to Expect

Prior to undergoing a CT KUB, the patient may have to remove some items of clothing, accessories, jewelry and metals, as these are often radio-opaque, and may interfere with the process and the quality of the results.

Any medications taken in the days beforehand have to be communicated to the radiologist to ensure that they are not contraindicated for the procedure. Furthermore, the possibility of pregnancy has to be ruled out in order to avoid unnecessarily exposing the developing baby to the teratogenic effects of radiation.

The patient is either placed in the supine or prone position into the CT scanner and has to remain still during the procedure. There is an advantage in the prone position, because it allows for better assessment of urinary stones at the vesicoureteral junction. CT KUB views are painless, but last a little longer in duration than conventional KUB radiographs.

Nonetheless, they are still quick and the technology is readily accessible, providing data which enables identification of genitourinary and intestinal pathologies. The results are examined by a radiologist, who then creates a report of the findings and sends it to the physician who is in charge of treating the patient.

Risks

Exposure to ionizing radiation is the main risk factor associated with the CT KUB procedure. This can cause damage to biological tissues and increase the propensity, albeit small, of developing cancer in the future.

This risk is cumulative over one’s lifetime and is but a small price to pay for managing acute conditions that could be life-threatening and require urgent imaging. In pregnancy, alternative imaging modalities, where possible, such as ultrasound or MRI, which do not expose the pregnant woman to ionizing radiation, are preferred.

References

• https://radiopaedia.org/articles/ct-kub
• https://www.nibib.nih.gov/science-education/science-topics/computed-tomography-ct

Further Reading

• All Radiography Content
• KUB Radiography
• Digital Radiography
• Digital Radiography versus Computed Radiography