CT KUB: Benefits, risks, preparation, and how it’s done


Computed tomography (CT scan or CAT scan) is a noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.

CT scans of the kidneys can provide more detailed information about the kidneys than standard kidney, ureter, and bladder (KUB) X-rays, thus providing more information related to injuries and/or diseases of the kidneys. CT scans of the kidneys are useful in the examination of one or both of the kidneys to detect conditions such as tumours or other lesions, obstructive conditions, such as kidney stones, congenital anomalies, polycystic kidney disease, accumulation of fluid around the kidneys, and the location of abscesses.


  • quick
  • easily accessible
  • identification of calcified renal tract calculi and their sequelae
  • assessment of other causes of flank pain if negative for calculus disease


exposure to ionising radiation

There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk. Radiation exposure during pregnancy may lead to birth defects. Therefore, the patient’s history should be taken carefully and a pregnancy test should be done before CT scan. Also, It is the responsibility of the referring physician to investigate the patient’s past record of radiation exposure, such as previous CT scans and other types of X-rays, so repetition of scans can be avoided. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time. The benefits vs risks of CT scan should be considered so unnecessary scan can be avoided. The risk of radiation exposure from CT is very small compared to the benefits especially when the CT scan is considered by the referring physician as an important tool for diagnosis according to the patient’s history and symptoms.


  • A radiology nurse or technologist will ask the patient a few questions regarding their medical history and allergies.
  • Explain the procedure to the patient.
  • The patient can eat, drink and take their prescribed medications prior to the exam unless IV contrast is requested.
  • The patient should drink some water before the scan. A full bladder is needed. A distended bladder is important to see stones clearly.
  • The patient may be asked to change into a patient gown. If so, a gown will be provided for them. A locker will be provided to secure personal belongings. Inform the patient to remove all piercings and leave all jewellery and valuables in the locker.

How it is done

  • The actual procedure will vary depending on institutional protocol/guidelines but below is a typical description:
  • Position the patient on the exam table, most often, the patient will be asked to lie flat on their back (supine) with both arms over the head.
  • some institutions may perform a limited pelvic scan in prone if the supine scan shows a calculus near the VUJ (vesicoureteric junction).
  • The table will slide into the scanner. The scanner is open at the back and the front, allowing the patient to see out.
  • The patient will be asked to hold very still and at times to hold the breath because movement causes blurred images.
  • The technologist should be always see and hear the patient during scanning.
  • This procedure usually takes approximately 5-10 minutes.


  • identification of calcified renal tract calculi size and position
  • stone composition assessment with dual energy CT
  • assessment of the sequelae of calculi (obstruction- infection)
  • assessment of other causes of flank pain if negative for calculus disease
  • a presence of further calculi at risk of obstructing

After The Scan

There are no restrictions placed on the patient after this procedure. They may eat and drive as normal.


Data interpretation with the use of axial, sagittal and coronal reformatted images for proper evaluation. The study will be read by a Radiologist (imaging physician) who specialises in the interpretation of CT scans. The results will be sent to the referring physician who will discuss these results with the patient and explain what they mean in relation to their health.



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