Is a prone (lying on the stomach) CT scan of the kidneys superior to the standard supine (lying on the back) technique?

CT Kidney Imaging: Prone vs. Supine Positioning

For most routine kidney CT imaging, prone positioning offers no clinically significant advantage over standard supine positioning and is not recommended as a routine practice. 1

Standard Positioning for Kidney CT

• Supine positioning is the established standard for CT imaging of the kidneys in clinical practice, as reflected in all major ACR Appropriateness Criteria guidelines for renal imaging 1

• The kidneys are retroperitoneal organs that are well-visualized in the supine position using standard CT protocols with or without IV contrast 1, 2

When Prone Positioning May Be Considered

CT Urography for Ureteral Opacification

• Prone positioning can improve distal ureteral opacification during CT urography (CTU) when complete visualization of the collecting system is required 3

• In a study of 70 patients, prone CT urography resulted in better opacification of the entire collecting system compared to supine technique, with distal ureteral visualization approaching that of traditional IV urography 3

• Abdominal compression combined with prone positioning provides the most reliable opacification of the distal ureters during excretory phase imaging 3

Ultrasound Imaging (Not CT)

• For ultrasound examination of the kidneys, prone or lateral decubitus positioning may facilitate visualization by using intercostal acoustic windows and spreading the ribs 1

• This positioning advantage applies to ultrasound only and does not translate to CT imaging 1

Kidney Mobility Considerations

• Research demonstrates that kidneys exhibit significant positional mobility between prone and supine positions, with mean axial plane movement of 13 mm on the left and 7 mm on the right 4

• However, this mobility does not impact diagnostic accuracy for routine kidney CT evaluation and is primarily relevant for interventional procedures like renal artery stenting 4

Practical Clinical Algorithm

For standard kidney CT indications:

• Use supine positioning for all routine renal CT imaging including evaluation of masses, infection, trauma, and stones 1

For CT urography requiring complete ureteral visualization:

• Consider prone positioning with abdominal compression if complete distal ureteral opacification is essential 3
• This is rarely necessary for routine clinical practice 5

For ultrasound (not CT):

• Use lateral decubitus or prone positioning to optimize intercostal windows 1

Common Pitfalls to Avoid

• Do not routinely use prone positioning for standard kidney CT as it provides no diagnostic benefit and may reduce patient comfort without improving image quality 1

• Do not confuse ultrasound positioning recommendations (where prone/decubitus helps) with CT positioning (where supine is standard) 1, 2

• If complete ureteral visualization is needed, specify CT urography with excretory phase imaging rather than changing patient position alone 5, 3