Evaluation of potential living kidney donors

Screening and selection of the primary method

Previously, ultrasound (US) was widely used for the initial screening of a potential donor. Its main objective was to confirm the presence of two healthy kidneys without overt anatomical anomalies.

However, the modern trend in diagnostic imaging is a shift toward exclusively CT-based evaluation (CT). Choosing comprehensive computed tomography significantly reduces the number of clinic visits and the total number of ordered tests while providing exhaustive information for transplant surgeons.

Step-by-step CT protocol

A comprehensive CT evaluation of a potential donor involves several strictly regulated stages, each aimed at visualizing specific anatomical structures:

1. Non-contrast CT (unenhanced CT): Performed at the very first stage. The primary goal is to reliably rule out renal calculi (renal calculi), which might be obscured by subsequent contrast administration.
2. Arterial phase (arterial phase): Scanning is performed from the upper abdomen down to the aortic bifurcation. This is necessary to reliably identify all accessory renal vessels (accessory renal vessels).
3. Coronal reconstruction (coronal reconstruction): Radiologists prefer to perform curved planar reconstructions strictly in the plane of the arteries. This approach provides a clear visualization of the vascular bed and precise identification of the bifurcation site.
4. Delayed phase: An additional scan performed at the 60th second of the examination. It is intended for detailed assessment of the anatomy of the renal veins (renal veins) and the inferior vena cava (cava).
5. Plain abdominal radiography (plain radiographs): Performed immediately after CT completion. It allows visualization of the renal-collecting system (renal-collecting system) and ureters (ureters), as well as reliably ruling out duplex collecting systems (duplex system) or obstruction.

Result evaluation and protocol compilation

In the final radiology report, the specialist must detail all relevant anatomical findings, as these determine the surgical strategy and the choice of the specific kidney for retrieval.

• Size and symmetry: Extremely precise measurement of both kidneys' dimensions is required. It is important to remember that a size discrepancy of more than 1 cm is an indication for further workup. In such cases, the patient is referred for DMSA radioisotope scintigraphy (DMSA scintigraphy).
• Exclusion of concomitant pathologies: It is critically important to rule out incidental renal masses (renal mass) and significant extrarenal anomalies. This vigilance is especially relevant when evaluating older donors, as the incidence of incidental clinical findings in this group is significantly higher.
• Arterial anatomy: The report records the exact number and location of all renal arteries. The presence of early vascular bifurcation close to the aortic trunk is specifically noted—these factors directly influence the choice of the organ for transplantation.
• Venous anatomy: The structure of the renal veins is described in detail. The radiologist must also note the presence of dilated lumbar (lumbar) or gonadal (gonadal) veins, which may complicate the surgical procedure.

Alternative method: MRI

In some cases, dynamic contrast-enhanced magnetic resonance imaging of the abdomen (dynamic MR imaging) may be used to evaluate potential donors. The final choice of imaging modality always depends on the preferences of the specific transplant center, the availability of high-end equipment, and the experience of the radiologists.

Nevertheless, MRI has several significant limitations compared to CT:

• It does not provide radiologists and surgeons with equivalent, highly accurate information regarding small calculi (calculi).
• The spatial resolution of magnetic resonance imaging in visualizing renal vessels may be inferior to the detail provided by multidetector computed tomography.

Class and exam questions

What else to study on this topic

• Kidney transplant complications: radiological presentation, early and late diagnosis
• Non-invasive radiology of vascular complications in kidney transplantation
• Helical CT in kidney transplantation: normal findings and complications
• Unenhanced MR angiography: techniques and clinical applications in patients with renal disease

Other topics in the section "Diagnostic Radiology of the Abdominal Organs"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.