Noncontrast-Enhanced Magnetic Resonance Versus Computed Tomography Angiography in Preoperative Evaluation of Potential Living Renal Donors

Radiologic evaluation of the kidney transplant donor and recipient

The kidney is the most common solid organ transplant globally and rates continue to climb, driven by the increasing prevalence of end stage renal disease (ESRD). Compounded by advancements in surgical techniques and immunosuppression leading to longer graft survival, radiologists evermore commonly evaluate kidney transplant patients and candidates, underscoring their role along the transplant process. Multiphase computed tomography (CT) with multiplanar and 3D reformatting is the primary method for evaluating renal donor candidates, detailing renal size, vascular/collecting system anatomy, and identifying significant pathologies such as renal vascular diseases and nephrolithiasis. Ultrasound is the preferred initial postoperative imaging modality for graft evaluation due to its low cost, accessibility, noninvasiveness, and lack of radiation. CT and magnetic resonance imaging (MRI) may be useful adjunctive imaging techniques in diagnosing transplant pathology when ultrasound alone is not diagnostic. Kidney transplant complications are categorized by an approximate timeline framework, aiding in differential diagnosis based on onset, duration, and severity and include perinephric fluid collections, graft compression, iatrogenic injuries, vascular compromise, graft rejection, and neoplastic processes. This review discusses imaging strategies and important findings along the transplant timeline, from donor assessment to long-term recipient complications.

One-stop preoperative assessment of renal vessels for living donors with 3.0 T non-contrast-enhanced magnetic resonance angiography: compared with computerized tomography angiography and surgical results

OBJECTIVE

The study was to investigate the feasibility and accuracy of assessment for living renal donors before transplantation by using 3.0 T non-contrast-enhanced magnetic resonance angiography (NCE-MRA).

METHODS

30 renal donors were investigated and underwent computed tomography angiography (CTA) and 3.0 T NCE-MRA before nephrectomy. Two radiologists independently assessed arterial and venous anatomy and potential kidney lesions. The image quality score, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), diameters and lengths of renal arteries and veins were compared between CTA and NCE-MRA. Imaging findings were compared with the surgical results served as reference standard. Agreement was assessed using κ test. The Wilcoxon test and paired sample t test were used for statistically significant differences.

RESULTS

The results of image quality score for renal arteries and veins were highly consistent between the two radiologists in NCE-MRA (p < 0.001). There was no significant difference in the scores of renal arterial and venous branches between NCE-MRA and CTA (p > 0.05). The SNR and CNR of renal vessels were higher than CTA (p < 0.001). There were no statistically significant differences in the length of renal vessels measured by the two methods (p > 0.05), and the diameter was smaller than that of CTA (p < 0.05). The detection of normal renal arteries and early branches by both examination techniques was consistent with intraoperative findings. Both methods showed good consistency between the anatomical variation of renal vein and the intraoperative diagnosis (p < 0.001).

CONCLUSION

3.0 T NCE-MRA can be used for evaluation of main renal arteries and veins with high accuracy for anatomy and variation classification, and can be used for pre-operative vascular evaluation of living donor kidney transplantation.

ADVANCES IN KNOWLEDGE

3.0 T NCE-MRA can be used for evaluation of main renal arteries and veins with high accuracy for anatomy and variation classification, and can be used for pre-operative vascular evaluation of living donor kidney transplantation.

Unenhanced magnetic resonance angiography as an accurate alternative in the preoperative assessment of potential living kidney donors with contraindications to computed tomography angiography and to contrast-enhanced magnetic resonance angiography

Objective

To evaluate the accuracy of steady-state free precession (SSFP) unenhanced magnetic resonance angiography (MRA) at 1.5 T for the identification of multiple renal arteries, using computed tomography angiography (CTA) as the reference standard.

Materials and Methods

This was a prospective study involving 39 patients (26 males; mean age, 62.6 years) who underwent CTA and unenhanced MRA to evaluate the proximal and middle segments of the renal arteries. The analysis was performed in two phases: the quality of unenhanced MRA images was classified as diagnostic or nondiagnostic for the presence of multiple renal arteries by two independent readers; two other independent readers then evaluated the images previously classified as being of diagnostic quality. The sensitivity, specificity, and overall accuracy of unenhanced MRA were calculated, CTA being used as the reference standard. The kappa statistic was used in order to calculate interobserver agreement.

Results

The image quality of unenhanced MRA was considered diagnostic in 70-90% of the extrarenal arterial segments. The CTA examination revealed 19 multiple renal arteries (8 on the right and 11 on the left). The accuracy of unenhanced MRA for the identification of multiple renal arteries was greater than 90%, with a sensitivity of 72.7-100% and a specificity of 96.3-100%.

Conclusion

Unenhanced MRA provides high quality imaging of the extrarenal segments of renal arteries. This method may be used as an alternative for the evaluation of the renal arteries, given that it has an accuracy comparable to that of CTA.

Robotic assisted nephrectomy for living kidney donation (RANLD) with use of multiple locking clips or ligatures for renal vascular closure

Background

Robotic assisted nephrectomy for living donation (RANLD) is a rapid emerging surgical technique competing for supremacy with totally laparoscopic and laparoscopic hand assisted techniques. Opinions about the safety of specific techniques of vascular closure in minimally invasive living kidney donation are heterogeneous and may be different for laparoscopic and robotic assisted surgical techniques.

Methods

We retrospectively analyzed perioperative and short-term outcomes of our first (n=40) RANLD performed with the da Vinci Si surgical platform. Vascular closure of renal vessels was performed by either double clipping or a combination of clips and non-transfixing suture ligatures.

Results

RANLD almost quintupled in our center for the observed time period. A total of n=21 (52.5%) left and n=19 (47.5%) right kidneys were procured. Renal vessel sealing with two locking clips was performed in 18 cases (45%) Both, clips and non-transfixing ligatures were used in 22 cases (55%). Mean donor age was 53.075±11.68 years (range, 28–70). The average total operative time was 150.75±27.30 min. Right donor nephrectomy (139±22 min) was performed significantly faster than left (160.95±27.93 min, P=0.01). Warm ischemia time was similar for both vascular sealing techniques and did not differ between left and right nephrectomies. No conversion was necessary. Clavien-Dindo Grade ≤IIIb complications occurred in (n=5) 12.5%. Grade IV and V complications did not develop. In particular no hemorrhage occurred using multiple locking clips or suture ligatures for renal vascular closure. Mortality was 0%. Thirteen kidneys (32.5%) were transplanted across the AB0 barrier.

Conclusions

RANLD is an emerging minimally invasive surgical technique which facilitates excellent perioperative and short-term outcomes also when using multiple locking clips or suture ligatures for renal vascular closure.

Vascular imaging in renal donors

Imaging plays a crucial role in pre-transplant evaluation to enhance the probability of a successful outcome. Its aim is to define kidney and vascular anatomy and to assess potential pathologies. Each modality has advantages and disadvantages. Computed tomography angiography (CTA) is the most commonly used imaging modality, however, magnetic resonance angiography (MRA) can be used in selected cases. The purpose of this review article is to provide an overview of available imaging modalities, their benefits, risks, advantages, and disadvantages. Imaging findings that indicate particular anomalies and pathologies that may affect living renal donor selection will be discussed.

Preoperative evaluation of renal artery in patients with renal tumor: Using noncontrast-enhanced magnetic resonance angiography

To investigate the feasibility of the noncontrast-enhanced magnetic resonance angiography (NCE-MRA) to evaluate renal arteries before partial nephrectomy (PN).Retrospective analyzed 479 patients who underwent renal surgery between January 2013 and December 2015 with NCE-MRA or computed tomographic angiography (CTA) renal artery image reconstruction preoperative in our department. The renal artery reconstruction score (RARS) was based on the level of artery visualization in a 4-class criterion, and the R.E.N.A.L nephrometry score (R.E.N.A.L), arterial based complexity (ABC) were also analyzed.Of the 479 patients, the overall-lever RARS was 3.62, and the average in 2 groups was no significant difference (NCE-MRA vs CTA, P = 0.072). The performance of NCE-MRA in PN group was similar with CTA. Further comparison demonstrated that the efficiency of NCE-MRA in moderate- or low-degree tumor according to the R.E.N.A.L and ABC complexity less than 3S was equal to CTA. However, high degree (P < 0.001), 3S (P = 0.027), or 3H (P < 0.001) would affect the imaging of renal artery. Intragroup analysis showed that tumor complexity such as max tumor size (r = -o.351, P < 0.001), R.E.N.A.L (r = -0.439, P < 0.001), and ABC (r = -0.619, P < 0.001) were closely correlated with the NCE-MRA performance. The images of 2 sides of the kidney were compared in single person as well, which was meaningful for NCE-MRA patients only (NCE-MRA, P < 0.001; CTA, P = 0.182).The renal artery reconstruction performed by NCE-MRA is feasible and has a similar achievement in the PN potential recipients, with a lower side effect, and meets the requirements for making surgical decision. It has a broad application prospect in clinical practice; however, it still needs to further improve the ability in more complex tumors.