CT kidneys, ureters and bladder (protocol)

Last revised by Travis Fahrenhorst-Jones on 18 Apr 2022

Computed tomography of kidneys, ureters and bladder (CT KUB) is a quick non-invasive technique for diagnosis of urolithiasis. It is usually considered the initial imaging modality for suspected urolithiasis in an emergency setting 1.

NB: This article is intended to outline some general principles of protocol design. The specifics will vary depending on CT hardware and software, radiologists' and referrers' preference, institutional protocols, patient factors (e.g. allergy) and time constraints. 

Indications
  • suspected urolithiasis 
  • hematuria (typically in conjunction with a CT-IVU)
  • flank pain
Purpose

The purpose of CT KUB is primarily to assess for the presence of urolithiasis. Location of the stone, size, and secondary signs of renal tract obstruction can then be used to gauge the likelihood of passage and guide further management 3

Technique
  • patient position
    • supine with their arms above their head
  • scout 
    • above the diaphragm to the below pubic symphysis 
  • scan extent 
    • above kidneys to below pubic symphysis 
  • scan direction
    • caudocranial
  • contrast injection considerations
    • non-contrast
  • scan delay
    • minimal scan delay
  • respiration phase
    • inspiration 

Practical points

  • prone has the advantage of assessing stones near the vesicoureteric junction which may have just passed
  • some institutions may perform a limited pelvic scan in prone if the supine scan shows a calculus near the vesicoureteric junction
  • stone composition assessment can be done with dual energy CT

Findings

  • identification of calcified renal tract calculi size and position
  • assessment of the sequelae of calculi
    • obstruction
    • infection
  • assessment of other causes of flank pain if negative for calculus disease
  • presence of further calculi at risk of obstructing

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Cases and figures

  • Case 1: normal CT KUB
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  • Case 2: obstructing right ureteric calculus
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  • Case 3: stone near VUJ
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  • Case 4: passed ureteric stone
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  • Case 5: sigmoid diverticulitis
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