What is the imaging modality of choice for kidney donor patients?

Imaging of Choice for Kidney Donor Patients

CT angiography (CTA) is the imaging modality of choice for evaluating potential living kidney donors, as it provides comprehensive anatomical assessment of renal vasculature, parenchyma, and collecting systems necessary for surgical planning. 1

Primary Recommendation: CT Angiography

Renal imaging (specifically CT angiography) should be performed in all donor candidates to assess renal anatomy before nephrectomy. 1 This is the standard approach used by centers in the United States because of:

• Ease of interpretation by surgeons - CTA provides clear anatomical detail that transplant surgeons can readily use for operative planning 1
• Completeness of information - CTA visualizes main renal arteries with 100% sensitivity and detects 93% of accessory arteries identified at surgery 2
• Comprehensive evaluation - Single study assesses arterial anatomy, venous anatomy, parenchymal abnormalities, and collecting system anatomy 3

Critical Technical Requirements

The radiologist must understand the laparoscopic nephrectomy procedure to convey important surgical information, including: 1

• Number and location of renal arteries (multiple arteries require experienced surgeons) 1
• Renal vein length (particularly important for right-sided donation due to shorter right renal vein) 1
• Presence of vascular anomalies such as fibromuscular dysplasia or atherosclerotic disease 1
• Parenchymal abnormalities (cysts, masses, size discrepancies between kidneys) 1

Alternative Option: MR Angiography

MR angiography can be used in selected cases as an alternative to CTA, particularly when avoiding radiation exposure or iodinated contrast is prioritized. 3, 2

MRA provides comparable diagnostic accuracy: 2

• 100% sensitivity for main renal arteries and veins 2
• 90% detection rate for accessory arteries (slightly lower than CTA's 93%) 2
• No radiation exposure - important consideration for healthy donors 2
• No iodinated contrast - avoids potential nephrotoxicity 2

When to Choose MRA Over CTA

MRA is the preferred investigation when: 2

• Patient cannot tolerate iodinated contrast
• Minimizing radiation exposure is a priority in young donors
• Patient has contraindications to CT

Reserve CT angiography for patients unable to tolerate MR imaging. 2

Important Anatomical Considerations

Arterial Anatomy Assessment

Both CTA and MRA may miss small accessory renal arteries: 2

• CTA detects 93% of accessory arteries 2
• MRA detects 90% of accessory arteries 2
• Kidneys with 3 or more arteries should only be procured by surgeons with adequate experience 1

Laterality Decision-Making

In the absence of reasons to procure the right kidney (vascular, urological, or other abnormalities), the left kidney should be procured in laparoscopic donor nephrectomy because of the relative technical ease associated with a longer venous pedicle. 1

Right nephrectomy is appropriate when: 1

• Right kidney is clearly smaller than left
• Right kidney has lower function based on split kidney function
• Right kidney has abnormality such as large cyst
• Left side has significantly more complicated vascular anatomy

Contraindications Identified on Imaging

A donor candidate with atherosclerotic renal artery disease or fibromuscular dysplasia involving the orifices of both renal arteries should not donate. 1

Common Pitfalls to Avoid

• Failing to communicate surgical implications - The radiologist must specifically address findings relevant to laparoscopic technique, not just describe anatomy 1
• Underestimating accessory vessel significance - Small accessory arteries may be missed on imaging but discovered at surgery, requiring surgical expertise 2
• Inadequate venous assessment - Right renal vein length is critical for surgical planning and must be clearly documented 1
• Missing bilateral disease - Both kidneys must be thoroughly evaluated to ensure the "better" kidney remains with the donor 1