Elsevier

Clinical Imaging

Volume 40, Issue 3, May–June 2016, Pages 370-377
Clinical Imaging

Original Article
3.0 Tesla magnetic resonance angiography (MRA) for comprehensive renal evaluation of living renal donors: pilot study with computerized tomography angiography (CTA) comparison

https://doi.org/10.1016/j.clinimag.2016.01.010Get rights and content

Abstract

Purpose

Most living related donor (LRD) kidneys are harvested laparoscopically. Renal vascular anatomy helps determine donor suitability for laparoscopic nephrectomy. Computed tomography angiography (CTA) is the current gold standard for preoperative imaging; magnetic resonance angiography (MRA) offers advantages including lack of ionizing radiation and lower incidence of contrast reactions. We evaluated 3.0 T MRA for assessing renal anatomy of LRDs.

Materials and methods

Thirty consecutive LRDs underwent CTA followed by 3.0 T MRA. Data points included number and branching of vessels, incidental findings, and urothelial opacification. Studies were individually evaluated by three readers blinded to patient data. Studies were reevaluated in consensus with discrepancies revealed, and final consensus results were labeled “truth”.

Results

Compared with consensus “truth”, both computed tomography (CT) and magnetic resonance imaging were highly accurate for assessment of arterial and venous anatomy, although CT was superior for detection of late venous confluence as well as detection of renal stones. Both modalities were comparable in opacification of lower ureters and bladder; MRA underperformed CTA for opacification of upper urinary tracts.

Conclusions

3.0 T MRA enabled excellent detection of comprehensive renal anatomy compared to CTA in LRDs.

Introduction

The number of living donor renal transplants performed in the United States has greatly increased in recent years, with over 5700 living donor renal transplants performed in 2011 alone [1]. The majority of living related donors (LRDs) currently undergo laparoscopic renal harvest.

Preoperative imaging of donor renal vascular anatomy is critical for determining eligibility for laparoscopic nephrectomy as well as the kidney chosen for harvest. Factors for determining donor suitability and ease of laparoscopic nephrectomy include the number of renal arteries (RAs) and renal veins (RVs), the presence of early arterial bifurcation or late venous confluence, and incidental findings.

Early arterial bifurcation and late venous confluence can be variably defined. For the purposes of this study, commonly utilized criteria detailed below were chosen [2]. Early bifurcation of the RA was defined as bifurcation of the left RA less than 2 cm from the left lateral aspect of the aorta or of the right RA posterior to the inferior vena cava (IVC). With laparoscopic harvest, early bifurcation may result in two small caliber arteries rather than one larger artery, which can make arterial anastomosis in the allograft recipient more challenging. Surgeons usually prefer a length of approximately 1.5–2 cm from the aorta to the first arterial branch point to perform adequate anastomosis of the donor kidney and decrease postoperative complications.

Late confluence of the RV was defined as the left RV branches coalescing less than 1.5 cm from the left lateral aspect of the aorta or the right RV branches coalescing less than 1.5 cm from the IVC. With laparoscopic harvest, late confluence may result in two small caliber veins rather than one larger vein, which can make venous anastomosis in the renal recipient more challenging.

Incidental renal findings including stones, renal lesions such as incidental renal mass, duplicated collecting systems, hydronephrosis, or scarring also influence donor suitability as well as the kidney chosen for harvest.

Historically, preoperative evaluation of living renal donors was performed with intravenous urography and angiography. These imaging modalities allowed for adequate visualization of RAs and the collecting system. However, given the limited exposure and visibility of a laparoscopic approach, preoperative visualization of the renal venous anatomy became critical to provide for surgeons [3]. During a laparoscopic donor nephrectomy (LDN), venous bleeding can lead to significant blood loss and possible conversion to open nephrectomy [4]. Computed tomography angiography (CTA) is the current gold standard for preoperative imaging of renal donors, and the vascular anatomy correlates very closely with laparoscopic anatomy [2]. Magnetic resonance angiography (MRA) offers a number of inherent advantages over computed tomography (CT), including lack of ionizing radiation and a lower incidence of adverse reactions to gadolinium-based magnetic resonance (MR) contrast agents compared with iodinated contrast used for CTA [5].

Though the performance of both CTA and MRA have been reported independently, there have been only a few direct comparative studies to determine their relative efficacy in preoperative imaging of LRDs with inconsistent results [6]. In this study, we compared the performance of multidetector CTA to 3.0 T MRA in the same donor population to determine the relative performance of each modality.

Section snippets

Patient accrual

Over a 2-year period, 30 consecutive prospective LRDs (17 women and 13 men, age range 20–63 years, mean age 42.7 years with an SD of 12.9) underwent sequential CTA and MRA according to the protocols below for planning of prospective laparoscopic renal donor surgery. The institutional review board approved this prospective study. Informed consent was acquired from all subjects in compliance with the 1996 Health Information, Privacy and Portability Act. Twenty-five donors underwent 64-multidetector

Results

Comparison of MRA to CTA in anatomic assessment of potential renal donors demonstrated the high accuracy of both modalities. Compared to CTA, MRA was excellent in detection of RAs and RVs, as well as in detection of early arterial bifurcation. MRA was significantly less sensitive and accurate than CTA in detection of late venous confluence. CTA was subjectively superior to MRA in urothelial opacification in the excretory phase. MRA missed two small renal calcifications detected by MRA; all

Discussion

LDN, a technique introduced in 1995 [7], has become the preferred method to harvest a kidney from an LRD. Compared with open nephrectomy, LDN offers decreased morbidity, quicker recovery time, less pain, and improved cosmesis [8]. There is a steep learning curve associated with mastering LDN, as the surgery offers limited field of view, especially with regard to posterior renal vessels, when compared with open nephrectomy [9], [10].

In general, the left kidney is preferred for LDN. The left

Conclusion

This was the first direct cohort comparison of 3.0 T MRA with multidetector CTA in the comprehensive evaluation of renal anatomy of LRDs. The results suggest that 3.0 T MRA is comparable to CTA for evaluating the renal anatomy and urinary tract in individuals unable to tolerate CTA for various reasons. CTA more reliably depicts small veins and their branching patterns, as well as small renal calcifications.

Acknowledgments

The authors acknowledge the support of Gabriel Danovitch, M.D., and the UCLA Kidney & Pancreas Transplant Program.

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  • Cited by (5)

    Mailing address of all authors at the time this study was done: Abdominal Radiology, Ronald Reagan UCLA Medical Center, Westwood Plaza Suite 1621, Los Angeles, CA, 90095-1721.

    Grants: None

    Disclosures: None

    1

    Present address: Department of Radiology, University of Southern California Keck School of Medicine, 1500 San Pablo Street, 2nd Floor Imaging, Los Angeles, CA 90033.

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