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Evaluation of Living Renal Donors: Accuracy of Three-dimensional 16-Section CT¹

¹ From the Departments of Radiology (N.R., D.V.S., M.A.B., P.R.M.) and Transplant Surgery (D.C.K.), Massachusetts General Hospital, 55 Fruit St, White 270, Boston, MA 02114. Received May 6, 2005; revision requested July 5; revision received August 14; accepted September 12; final version accepted October 4. Address correspondence to D.V.S. (e-mail: dsahani{at}partners.org).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 
Purpose: To retrospectively assess the sensitivity and specificity of three-dimensional (3D) 16-section computed tomography (CT) in the evaluation of vessels, pelvicalyceal system, and ureters in living renal donors, with surgical findings as the reference standard.

Materials and Methods: This was a HIPAA-compliant study. Institutional review board approval was obtained for the review of subjects' medical records and data analysis, with waiver of informed consent. Forty-six renal donors (18 men, 28 women; mean age, 42 years) were examined with 16-section CT. Two blinded reviewers independently studied renal vascular and urographic anatomy of each donor CT scans by fist using 3D images alone, then transverse images alone, and finally transverse and 3D data set. Image quality, degree of diagnostic confidence, and time used for review were recorded. Sensitivity and specificity were calculated.

Results: For 3D images, transverse images, and transverse in conjunction with 3D data sets, the respective sensitivity and specificity of CT in evaluation of accessory arteries by reviewer 1 were 100% and 100%, 89% and 100%, and 100% and 100%, and those by reviewer 2 were 89% and 97%, 89% and 100%, and 89% and 100%; the respective sensitivity and specificity in evaluation of venous anomalies by reviewer 1 were 100% and 98%, 100% and 98%, and 100% and 98%, and those by reviewer 2 were 100% and 98%, 100% and 95%, and 100% and 98%. For focused comprehensive assessment of renal donors with 3D scans alone, a reviewer on average (average of reviewers 1 and 2) used 2.4 minutes per scan, demonstrated full confidence in 93%, and rated the quality as excellent in 76%.

Conclusion: For focused assessment of renal vascular and urographic anatomy, review of 3D data set alone provides high sensitivity and specificity with regard to findings seen at surgery.

© RSNA, 2006

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 
Renal transplantation represents the best available replacement treatment for patients with end-stage renal disease. Living donor renal transplantation has been shown to clearly have better recipient and renal graft survival rates than cadaver graft survival rates (1,2). Increasing numbers of donor nephrectomies performed with a laparoscopic approach at most major transplant programs in the United States have contributed to a substantial growth in living kidney donation (3,4). The minimally invasive laparoscopic technique offers a statistically significant reduction in the length of hospital stay, need for intravenous analgesics, time to resumption of diet, and early return to normal daily activities (2–5).

Preoperative imaging work-up of living renal donors involves anatomic and functional evaluation of donor kidneys for selection of a suitable donor and for planning surgery (6–10). Therefore, preoperative mapping of renal vascular anatomy constitutes a major focus of kidney donor imaging (6,7,10). Three-dimensional (3D) multi–detector row computed tomographic (CT) angiography is now considered a clinically appealing alternative to conventional angiography in the assessment of renal vascular anatomy of potential living renal transplant donors (11–18).

The addition of more detector rows in helical CT from four to eight to 16 (and now up to 64) has increased the speed of scanning, thereby shortening the required breath holds for scanning. The 16-section CT scanner allows acquisition of near isotropic voxels of data with almost equal spatial resolution in the x-, y-, and z-axes. The increased speed of scanning eliminates motion artifacts and therefore enhances temporal resolution (19–21). These benefits have enhanced the quality of transverse, as well two-dimensional and 3D, images of renal anatomy (11,12,16). Thus, the purpose of our study was to retrospectively assess the sensitivity and specificity of 3D imaging data from 16-section CT in the evaluation of vessels, the pelvicalyceal system, and ureters in living renal donors by using surgical findings as the reference standard.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 
Subjects
This study was compliant with Health Insurance Portability and Accountability Act. Institutional review board approval was obtained for the review of subjects' medical records and data analysis, with waiver of informed consent. Of a total of 74 potential donors imaged during the period of July 2002 to August 2004, 46 who had surgical findings for comparison were included in the study population. The remaining 28 donors were either found to be unsuitable for donation or their names remained on the waiting list for surgery. There were 18 men and 28 women (mean age, 42 years; range, 26–59 years) who underwent donor nephrectomy.

Scanning Technique
Scanning was performed with a 16-section CT unit (LightSpeed 16; GE Medical Systems, Milwaukee, Wis) by using a standard technique for each subject. An initial low-dose precontrast scan of the abdomen was obtained from T12 to L5 vertebral levels by using 10-mm collimation, 18-mm table speed, 120 kV, and 70–140 mA. Subsequently, approximately 125–150 mL of nonionic iodinated contrast material containing 300 mg of iodine per milliliter (Isovue 300; Bracco Diag, Princeton, NJ) was injected intravenously thorough a 20-gauge cannula placed into an antecubital vein at a rate of 4–5 mL/sec by using a mechanical injector (E-Z-Em, Lake Success, NY). The Smart Prep option (automated software with scan triggering; GE Medical Systems) with a calculated 7-second scan delay after achievement of preset aortic attenuation of 125 HU was used for initiating the arterial phase imaging. This was followed by venous and excretory phases imaging at 65-second and 6-minute delays, respectively, from the time of initiation of contrast material injection.

To achieve a near isotropic volume resolution, a detector configuration of 16 sections at 0.6 mm was selected for each phase of scanning. A gantry rotation time of 0.5 second was used to shorten the scan time. Arterial phase scanning was performed by using a section thickness of 1.25 mm, intersection spacing of 0.6 mm, and table speed of 9.37 mm per rotation. Venous and excretory phase scanning were then performed by using a section thickness of 2.5 mm, table speed of 18.75 mm per rotation, and intersection spacing of 1.25 mm. Other parameters (0.5-second gantry rotation, 100–140 kV, 75–380 mA, and pitch of 0.938) were kept constant for each phase of scanning. Source images were then reconstructed at 50% overlap to preserve resolution and reduce partial volume effect.

Image Processing
The images of each renal donor CT examination were postprocessed with a commercially available workstation (ADW 3.1; GE Medical Systems) and a standard protocol by a trained technologist with more than 3 years of experience in image processing. Two-dimensional and 3D maps of renal arteries, veins, and ureters were generated by using maximum intensity projection (MIP), a volume-rendering technique, and multiplanar reformation. As a part of our dedicated 3D imaging postprocessing protocol, the following views were generated to evaluate renal anatomy in all donors: (a) coronal oblique MIP to show left and right renal arteries, including accessory and segmental arteries on either side; (b) coronal oblique MIP to show the renal vein, including major segmental tributaries, lumbar vein(s) on either side, and left adrenal and gonadal veins; (c) transverse MIP to show the relationship between renal artery and vein, including accessory artery and/or vein or any venous anomaly; (d) a batch of coronal MIPs with 5-mm thickness and 5-mm intersection spacing through the kidneys; (e) multiple gray-scale volume-rendered images of left and right kidneys for accurate demonstration of the aforementioned anatomy; and (f) 3D MIP or volume-rendered model from the 6-minute delayed images to demonstrate the pelvicalyceal system and ureters.

Image Analysis
Two fellowship-trained abdominal radiologists (D.V.S. [reviewer 1] and M.A.B., [reviewer 2] with 11 and 12 years, respectively, of radiology experience), who were blinded to surgical findings, independently reviewed each donor study with a picture archiving and communication system (Agfa-Impax 4.5, Richmond, Va) by using a defined pattern and sets of images: 3D images (MIP, volume-rendered images, and multiplanar reformation) alone first, followed by transverse images alone, and finally, transverse in conjunction with 3D data set at the same sitting. The average number of 3D, transverse, and transverse and 3D data sets reviewed in studying each donor examination was 35 (range, 25–65), 582 (range, 250–997), and 617 (range, 281–1032), respectively. In the assessment of each CT data set (3D or transverse), the order of donors was randomized. In addition, to eliminate any recall bias, a time gap of an average of 6 weeks (range, 4–8 weeks) was maintained in between the review of 3D images and the review of transverse images for each reviewer. After the review of transverse data set, postprocessed 3D images were provided to each reviewer, and their overall diagnosis, degree of confidence, and review time (in minutes) were recorded. During the review process of 3D images, both reviewers evaluated renal vessels in oblique transverse and oblique coronal planes while rotating the images of the kidneys in either plane.

For preoperative interpretations, several primary readers (n = 11; radiology experience, 5–25 years) independently reviewed transverse images, as well as multiplanar and 3D reconstructions in combination, of all donor CT examinations by using picture archiving and communication system. Electronic reports of these 46 living renal donors interpreted preoperatively by multiple readers were retrieved from the radiology database (N.R.). Reviewer 2 did not contribute to any of the prospective interpretations, but reviewer 1 was among one of the multiple readers. Eight weeks had elapsed before reviewer 1 started a blinded review.

For the blinded retrospective and initial prospective interpretations, findings of each donor CT examination were reviewed by using a predesigned template and systematic approach to generate a standardized report, which included information about renal size, cysts, calculi, renal artery fibromuscular dysplasia, or any other vascular or congenital disease. The number of renal arteries supplying each kidney and their location, the distance of first-order branch of renal artery from the aorta, and the number and size of accessory arteries were also recorded. An accessory artery was categorized according to its course as either polar (piercing the kidney directly) or hilar (entering the kidney at the hilum). A main renal artery division within 2 cm of the aorta was recorded as early branching. Likewise, information about renal venous anatomy such as location; number of renal veins; circumaortic or retroaortic anomalies; distance of gonadal, adrenal, and lumbar veins to inferior vena cava; and number of ureters and any anomaly of the collecting system was incorporated into the report. A length of less than 3 cm after the confluence of the major segmental veins on the right side was recorded as a short renal vein.

Many of the CT findings of donor anatomy are critical for surgery, but some do not substantially alter surgical management. Therefore, data recording of early renal artery bifurcation, diameter of accessory arteries, number and size of gonadal and adrenal veins, distance from their entrance into left renal vein to inferior vena cava, and delayed venous confluence of segmental renal veins were part of the multi–detector row CT reporting template but were not included for comparison with surgical findings at final data analysis in the current study.

Qualitative Assessment
At blinded interpretation, both reviewers independently rated the quality of 3D and transverse images and documented their degree of confidence with regard to how well the images reflected donor anatomy for all donors. For image quality, a subjective five-point scale was used, where score 1 indicated poor quality; score 2, suboptimal; score 3, diagnostic; score 4, superior; and score 5, excellent. It was a purely subjective scale on the part of the reviewers, wherein CT images with optimal homogeneous opacification of contrast material in vessels, pelvicalyceal system, and ureters were graded as excellent and those with inhomogeneous opacification of one or more of the aforementioned structures or presence of artifacts were graded as poor or of suboptimal quality. A similar five-point scale was used to grade the reviewer's confidence in studying each donor CT study with 3D images alone, transverse images alone, and transverse and 3D data sets combined, where a score of 1 indicated poor confidence; score of 2, some confidence; score of 3, diagnostic; score of 4, confident; and score of 5, full.

Standard of Reference
Renal vascular and ureteral findings at donor surgery constituted the standard of reference for all of the donors. Donor nephrectomies were performed by one of several transplant surgeons (n = 6), with 6–30 years of experience in renal transplantation surgery. Findings at surgery were dictated, and data were electronically stored as surgical reports. Information about the number of renal arteries supplying each kidney, their location, the distance of first-order branch of renal artery from the aorta, and the number and size of accessory arteries were recorded on each surgical report. Likewise, renal venous information such as location; number of renal veins; circumaortic or retroaortic anomalies; gonadal, adrenal, and lumbar veins; and number of ureters and any anomaly of the collecting system was recorded on a surgical report.

Electronic surgical reports of the 46 living renal donors were retrieved (N.R.) from the surgery database. On the basis of the available data of multi–detector CT imaging for blinded, as well as presurgical, interpretations and evidence at surgery, a comprehensive database was designed and the data were analyzed (N.R.). After the study, a combined interobserver agreement assessment was made between the two blinded reviewers to determine the final imaging consensus about CT donor examination(s) for which individual reviewer and surgical findings were not concordant.

Statistical Analysis
Any discrepancies between the findings made at CT and observations made at surgery were considered false-positive or false-negative for calculating the sensitivity, specificity, and accuracy of CT. On the basis of the presence or absence of variant renal vascular and ureteric anomalies at surgery, the sensitivity, specificity (with exact 95% confidence interval for each), and accuracy of 16-section CT, for blinded interpretations of two reviewers and initial prospective interpretations performed by 11 readers, were calculated by using statistical software (SAS version 9.1; SAS Institute, Cary, NC). Weighted statistics (SAS Institute) were used to quantify interobserver agreement between the two blinded reviewers in reviewing the 3D or transverse data set alone or transverse in conjunction with 3D data sets. A value of less than 0.20 was considered to represent poor agreement; value of 0.21–0.40, fair agreement; value of 0.41–0.60, moderate agreement; value of 0.61–0.80, good agreement; and value of 0.81–1.00, excellent agreement.

	RESULTS

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Both the reviewers at blinded retrospective interpretation and readers who performed the preoperative prospective interpretations recorded a single renal calculus measuring less than 4 mm in one donor kidney and a single simple renal cyst in two. At our institution, a kidney with small calculus or cyst is not a contraindication for donation and, in the absence of other overriding issues, should be the one selected, thus leaving the donor with the other unaffected kidney. None of the other donor kidneys were reported to have renal artery fibromuscular dysplasia or any other systemic vascular or congenital disease at CT.

On the basis of imaging findings, nephrectomy was performed in the left kidney in 39 donors and in the right kidney in seven. Among the latter seven donors, the right kidney was preferred mainly because of the presence of variant anatomy on the left side in six donors and a form of complete ureteral duplication on the right side in one donor. Nephrectomy was performed in the left kidney with an open flank approach in 16 of 39 donors and with a laparoscopic approach in the remaining 23. On the other hand, all nephrectomies in the right kidney were performed by using an open flank approach.

Renal Arteries
A total of 56 arteries in 46 kidneys were depicted at surgery; 37 (80.4%) kidneys had a single artery and nine (19.6%) had more than one (Figs 1 and 2), including two (Fig 3) in eight and three in one donor kidney (total number of accessory arteries at surgery, 10). Six of the nine kidneys with more than one artery were procured by using an open flank approach. In the remaining three left kidneys with a single accessory artery, laparoscopic procurement of the renal graft was successfully completed.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 1a: Vascular phase (a) MIP and (b) volume-rendered CT images in a 54-year-old female renal donor show dominant renal artery (arrowhead) supplying upper pole of right kidney and two accessory arteries (white arrows) supplying mid and lower pole each. Two renal veins (black arrows) are draining the right kidney. (c) Coronal arterial phase MIP CT image shows lower polar accessory (arrow) and dominant (arrowhead) arteries on the left side. Laparoscopic nephrectomy was performed in left kidney because of more favorable anatomy.

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 1b: Vascular phase (a) MIP and (b) volume-rendered CT images in a 54-year-old female renal donor show dominant renal artery (arrowhead) supplying upper pole of right kidney and two accessory arteries (white arrows) supplying mid and lower pole each. Two renal veins (black arrows) are draining the right kidney. (c) Coronal arterial phase MIP CT image shows lower polar accessory (arrow) and dominant (arrowhead) arteries on the left side. Laparoscopic nephrectomy was performed in left kidney because of more favorable anatomy.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 1c: Vascular phase (a) MIP and (b) volume-rendered CT images in a 54-year-old female renal donor show dominant renal artery (arrowhead) supplying upper pole of right kidney and two accessory arteries (white arrows) supplying mid and lower pole each. Two renal veins (black arrows) are draining the right kidney. (c) Coronal arterial phase MIP CT image shows lower polar accessory (arrow) and dominant (arrowhead) arteries on the left side. Laparoscopic nephrectomy was performed in left kidney because of more favorable anatomy.

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 2a: (a, b) Coronal MIPs from multidetector CT angiography in a 45-year-old female renal donor show dominant left renal artery (arrowhead) and small accessory artery (arrow in a), which appears to originate in proximity to dominant renal artery mimicking early division. (b) Rotated MIP depicts separate origin of accessory artery (arrow). (c) Corresponding transverse CT image shows separate origin of dominant (arrowhead) and accessory (arrow) arteries, which can be missed if data set is not carefully reviewed.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 2b: (a, b) Coronal MIPs from multidetector CT angiography in a 45-year-old female renal donor show dominant left renal artery (arrowhead) and small accessory artery (arrow in a), which appears to originate in proximity to dominant renal artery mimicking early division. (b) Rotated MIP depicts separate origin of accessory artery (arrow). (c) Corresponding transverse CT image shows separate origin of dominant (arrowhead) and accessory (arrow) arteries, which can be missed if data set is not carefully reviewed.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 2c: (a, b) Coronal MIPs from multidetector CT angiography in a 45-year-old female renal donor show dominant left renal artery (arrowhead) and small accessory artery (arrow in a), which appears to originate in proximity to dominant renal artery mimicking early division. (b) Rotated MIP depicts separate origin of accessory artery (arrow). (c) Corresponding transverse CT image shows separate origin of dominant (arrowhead) and accessory (arrow) arteries, which can be missed if data set is not carefully reviewed.

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 3: Coronal MIP from CT angiography in a 53-year-old female renal donor shows a dominant left renal artery (arrowhead) and lower polar accessory artery (arrow). A more surgically preferable laparoscopic nephrectomy in left kidney was performed.

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 4: Multi–detector row CT angiogram in a 39-year-old male renal donor shows one dominant renal artery (arrowhead) on the left and a smaller artery (arrow), which lies approximately 1 cm inferior to the dominant artery and was incorrectly read by one reviewer as an accessory artery. On retrospective review of 3D data set, this was found to be a branch of superior mesenteric artery crossing in front of left renal hilum.

Renal Veins
At surgery, 46 veins, including two with variant anatomy (left circumaortic in one and retroaortic vein in another donor kidney), were identified. All had a clearly visible single venous channel (including circumaortic and retroaortic veins in two left donor kidneys) without any accessory renal vein.

In evaluating 3D images alone or transverse in conjunction with 3D data sets, both reviewers recorded a total of 47 veins, including one circumaortic, one retroaortic (Fig 5), and one accessory (Fig 6), with a sensitivity of 100% and specificity of 98% ( = 1.0). In evaluating transverse images alone, reviewer 1 and reviewer 2 identified 47 and 48 veins, respectively, with 100% sensitivity and variable specificity (reviewer 1, 98% specificity; reviewer 2, 95% specificity; = 0.84) because reviewer 2 incorrectly identified an accessory vein on the right side in one donor (Table 1).

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 5a: Venous phase CT images in a 33-year-old renal donor with left retroaortic vein. (a, b) Transverse images show proximal (arrow in a) and distal (arrow in b) portion of left renal vein traversing behind aorta to drain into inferior vena cava. (c) Corresponding coronal MIP displays left retroaortic vein (arrow) anatomy.

View larger version (184K): [in this window] [in a new window] [Download PPT slide]   Figure 5b: Venous phase CT images in a 33-year-old renal donor with left retroaortic vein. (a, b) Transverse images show proximal (arrow in a) and distal (arrow in b) portion of left renal vein traversing behind aorta to drain into inferior vena cava. (c) Corresponding coronal MIP displays left retroaortic vein (arrow) anatomy.

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 5c: Venous phase CT images in a 33-year-old renal donor with left retroaortic vein. (a, b) Transverse images show proximal (arrow in a) and distal (arrow in b) portion of left renal vein traversing behind aorta to drain into inferior vena cava. (c) Corresponding coronal MIP displays left retroaortic vein (arrow) anatomy.

View larger version (166K): [in this window] [in a new window] [Download PPT slide]   Figure 6a: (a, b) Venous phase coronal CT MIPs in a 49-year-old female renal donor show a small accessory renal vein (arrow) on the right. Arrowhead = dominant right renal vein. Left kidney had two arteries (not shown). Open flank nephrectomy was performed in right kidney.

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 6b: (a, b) Venous phase coronal CT MIPs in a 49-year-old female renal donor show a small accessory renal vein (arrow) on the right. Arrowhead = dominant right renal vein. Left kidney had two arteries (not shown). Open flank nephrectomy was performed in right kidney.

Pelvicalyceal System and Ureters
At surgery, 44 of 46 kidneys had a normal single ureter. Partial and complete ureteral duplication were each found in the two remaining donor kidneys.

The pelvicalyceal system and the ureter above the iliac bifurcation were adequately opacified at CT in all 46 donor kidneys. Both reviewers at blinded interpretation in all defined settings and readers at prospective interpretation accurately recorded the normal ureter (n = 44) and ureteral anomalies (n = 2), including unilateral partial ureteral duplication (n = 1) in the left kidney and complete duplication (n = 1) in the right kidney.

Accuracy
The respective mean accuracy of 16-section CT angiography for evaluation of renal arterial, venous, and urographic findings by the two reviewers was 98%, 98%, and 100% for 3D images alone, 98%, 97%, and 100% for transverse images alone, and 99%, 98%, and 100% for transverse in conjunction with 3D data sets. The overall accuracy of CT for evaluation of renal arterial, venous, and urographic findings on prospective interpretations performed by the 11 readers was 98%, 93%, and 100%, respectively.

Qualitative Assessment
For subjective assessment of 3D image quality, reviewer 1 graded five as superior and 40 as excellent and reviewer 2 graded 16 as superior and 30 as excellent. For assessment of transverse image quality, reviewer 1 graded 10 as superior and 33 as excellent and reviewer 2 graded 20 as superior and 26 as excellent (Table 2). Reviewer 1 and reviewer 2 respectively demonstrated full confidence in 46 and 40 3D images alone and in 41 and 12 transverse images alone (Table 2).

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 
Conventional angiography was long considered the standard imaging technique for the evaluation of renal arteries in a living donor candidate (11,13,22,23). Recently, CT angiography with helical multi–detector row technology and multiplanar reconstructions has become the imaging technique of choice (14–16,24–26). However, this technology has resulted in a substantial increase in the number of images acquired, which may pose a challenge for the radiologist to review efficiently and in a timely fashion. Therefore, we wanted to assess if review of 3D images alone can allow accurate evaluation of the donor anatomy.

In our series of 46 consecutive renal donors, review of 3D images alone for renal arteries provided results with excellent diagnostic confidence and high sensitivity and specificity with respect to the surgical findings. The interobserver agreement for the review of 3D images alone was also excellent ( = 0.86). Even smaller sized accessory renal arteries, measuring less than 2 mm in diameter, were confidently identified on 3D images alone. However, there may be a necessary learning curve with interpretation of two-dimensional and 3D images alone. For example, a small artery or vein crossing anterior to the kidneys may be mistaken for an accessory renal artery or vein. We believe a false-positive diagnosis is indeed more likely with review of MIP images alone. The major disadvantage of selecting pixels with an MIP is that all enhanced vessels will be displayed along with the renal vessels, which imposes some difficulty in distinguishing accessory renal arteries from lumbar and other vessels crossing the kidney. This issue can be potentially obviated with careful review of both MIP and volume-rendered images. In our study, one of the blinded reviewers at evaluation of 3D images alone incorrectly identified one accessory artery. On consensus review, this was agreed to be a small branch of the superior mesenteric artery that crossed anterior to the hilar region of the left kidney.

Both reviewers at blinded evaluation of the transverse images alone missed a smaller apical accessory artery supplying the left kidney that was identified in consensus on careful retrospective review of the 3D images, which reflects the importance of the routine use of 3D images in the evaluation of vascular anatomy of the donors. In addition, with the advent of faster scanners, it is now more critical than ever to coordinate scanning with an appropriate contrast material injection strategy to acquire a true arterial phase. Bolus tracking or automated scan triggering is highly desirable to generate excellent-quality angiograhic images. Therefore, to ensure consistency, we used a Smart Prep technique with automated triggering of contrast material in all of our donor examinations. In addition, to maintain consistency, a standard postprocessing protocol was used for each examination, which allowed acquisition of the specific views by using MIP and volume rendering to display the donor anatomy for focused rapid reviewing.

The overwhelming increase in the number of images acquired with a 16-section scanner virtually mandates the use of a picture archiving and communication system. In our study, CT in a renal donor produced 582 transverse images on average. Review of such a large data set is a challenge not only for radiologists but also for display and storage media. On average in our study, each of the two blinded reviewers studied 35 images per donor CT while reviewing 3D images alone. The reduced number of 3D images relative to the transverse data set facilitates focused and rapid renal vascular and pyelographic assessment with an appealingly more immediate overview of the pertinent anatomy. The average total review times of the two blinded reviewers for studying 3D and transverse images were 2.4 and 4.1 minutes, respectively. Therefore, a comprehensive evaluation of renal donor anatomy can be performed with a relatively quick review of the 3D data set alone. The majority of 3D images were graded as of excellent quality.

When the results of blinded reviewers are considered, we believe that evaluation of renal vascular, pelvicalyceal, and ureteral findings on 3D images alone obtained with a 16-section CT saves radiologist's review time and provides results with high sensitivity and specificity and good diagnostic confidence. The difference in the degree of diagnostic confidence of the two reviewers may be due in part to the relatively greater experience of reviewer 1 (4 years) compared with that of reviewer 2 (6–8 months) in interpreting renal donor CT images. The combination of 3D and transverse data sets increases review time but allows the reviewer to concentrate on other imaging findings on the transverse images. Furthermore, 3D images may also help surgeons by providing them with fewer and relevant images of the donor anatomy, and the images may be displayed in the operating room in a way the surgeons are familiar with from surgery, rather than confining them to the traditional imaging format of a transverse data set. The overall results of our study support review of 3D images alone as a single focused method for evaluating renal vascular and pyelographic findings in potential renal donors. Clearly, more studies will need to be performed to validate these results and generate multicenter consensus.

There were limitations to our study. First, this was a retrospective analysis; therefore, the possibility of an inadvertent bias cannot be excluded. Furthermore, the findings at surgery constituted a reference standard for renal vasculature and ureteral anatomy, and the surgeons were not asked to rate the quality of 3D or transverse images with regard to how well and accurately they reflected the donor anatomy for surgical planning. Also, surgeons preferentially selected kidneys with normal or less intricate anatomy for transplantation. Therefore, the true performance of reviewing the 3D images for evaluating more complex renal vascular and excretory anatomy and anomalies could not be directly compared. This also reflects on our results, since no significant difference in the performance of blinded readers in reviewing 3D images alone or in combination with the transverse data set was observed.

In conclusion, review of the 3D data set alone by using 16-section CT can provide focused renal vascular, pelvicalyceal system, and ureteral results with high sensitivity and specificity and good diagnostic confidence, thereby reducing the necessary interpretation time.

	ADVANCES IN KNOWLEDGE

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 

• Review of a 3D data set alone for focused assessment of renal vessels, the pelvicalyceal system, and ureters of living donors provides high sensitivity and specificity with regard to findings at surgery.
  
• Focused review of renal vessels, pelvicalyceal system, and ureters on 3D images alone of a donor study performed with 16-section CT saves radiologist's review time and provides results with full diagnostic confidence.
  

	ACKNOWLEDGMENTS

 
The authors acknowledge the input of Elkan Halpern, PhD, for the statistical analysis.

	FOOTNOTES

 

Abbreviations: MIP = maximum intensity projection • 3D = three-dimensional

Authors stated no financial relationship to disclose.

Author contributions: Guarantor of integrity of entire study, D.V.S.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, N.R.; clinical studies, D.V.S., M.A.B., D.C.K.; statistical analysis, N.R.; and manuscript editing, all authors

	References

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 

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