(Radiographics. 2001;21:S223-S236.)
© RSNA, 2001
Evaluation of Prospective Living Renal Donors for Laparoscopic Nephrectomy with Multisection CT: The Marriage of Minimally Invasive Imaging with Minimally Invasive Surgery1
Jonas Rydberg, MD,
Kenyon K. Kopecky, MD,
Mark Tann, MD,
Scott A. Persohn, RT,
Stephen B. Leapman, MD,
Ronald S. Filo, MD and
Arieh L. Shalhav, MD
1 From the Departments of Radiology (J.R., K.K.K., M.T., S.A.P.), Urology (A.L.S.), and Surgery (S.B.L., R.S.F.), Indiana University Hospital, 550 N University Blvd, Rm 0279, Indianapolis, IN 46202-5253. Recipient of a Certificate of Merit award for an education exhibit at the 2000 RSNA scientific assembly. Received February 2, 2001; revision requested March 6 and received April 20; accepted April 25. Address correspondence to J.R. (e-mail: jrydberg@iupui.edu).
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Abstract
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Laparoscopic technique for excision of a kidney from a living donor has advantages over conventional open surgery, but operative visibility and surgical exposure are limited. Preoperative multisection computed tomography (CT) can provide necessary anatomic information in a minimally invasive procedure. A three-phase examination is suggested: (a) imaging from the top of the kidneys to the pubic symphysis with a section width of 2.5 mm and no contrast medium, (b) scanning of the kidneys and upper pelvis during the arterial phase of enhancement with a section width of 1.0 mm, and (c) scanning of the kidneys and upper retroperitoneum during the nephrographic phase of enhancement with a section width of 1.0 mm. Emphasis in this article is placed on analysis of the venous anatomy because most radiologists are unfamiliar with the anatomic variations. Conventional radiography of the abdomen and pelvis is performed after CT to evaluate the collecting system and ureters and to provide a lower total radiation dose than if CT were used. Of several postprocessing techniques that may be used, the authors prefer maximum intensity projection for arterial evaluation and multiplanar reformatting for venous evaluation.
Index Terms: Kidney, CT, 81.12119 • Kidney, transplantation, 81.455 • Renal arteries, CT, 961.12919 • Renal veins, CT, 966.12919
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LEARNING OBJECTIVES FOR TEST 5
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After reading this article and taking the test, the reader will be able to:
- Describe the multisection CT scanning protocol for renal donor evaluation.
- Evaluate potential donors for contraindications to renal donation.
- Evaluate the renal arterial and venous anatomy.
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Introduction
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Laparoscopic nephrectomy in living renal donors was introduced in 1995 (1). Compared with open nephrectomy, the laparoscopic procedure offers advantages for the donor such as less time in the hospital, less postoperative pain, fewer cosmetic concerns, and less convalescence time (2–4). Potential living renal donors must undergo screening to determine their suitability for donation. Imaging is part of this screening. By tradition, living renal donors have undergone evaluation with excretory urography and renal angiography. Excretory urography depicted renal size, stone disease, and pelvicaliceal anatomy, whereas angiography provided information about the renal arterial anatomy. Both methods failed to depict small stones, subtle masses, and detailed information about venous abnormalities. Several studies have shown that evaluation of potential renal donors with excretory urography and renal angiography can be replaced with helical computed tomography (CT) (5–11). CT also allows definition of the renal venous anatomy, including the renal vein, adrenal vein, gonadal vein, and lumbar veins (7,8). The left kidney is preferred for laparoscopic surgery. Most surgeons will accept donors with one or two accessory renal arteries. Surgeons need complete information about the venous anatomy because venous bleeding is a potentially serious complication of laparoscopic surgery that sometimes requires the conversion of a laparoscopic procedure to an open one.
Multisection CT, with acquisition of four sections at a time, was introduced in 1998. Multisection CT examinations can be performed with thinner section thickness and shorter acquisition time than can single-section CT. The preoperative evaluation of renal donors with multisection CT can provide a more detailed and sensitive analysis of the renal vasculature and pathologic conditions than before.
Exclusion criteria for laparoscopic donor nephrectomy include unilateral agenesis, renal ectopia, horseshoe kidney, urolithiasis, multiple renal arteries, renal arterial disease, complex venous anatomy (circumaortic or retroaortic left renal vein), renal neoplasm, hydronephrosis, cortical atrophy, medullary sponge kidney disease, renal papillary necrosis, retroperitoneal varices, and other abnormalities.
This article presents a technique for evaluating potential renal donors with multisection CT and displays clinical examples. Emphasis is placed on the analysis of the venous anatomy because most radiologists are unfamiliar with the anatomic variations. In addition, the veins are small and travel in many directions, providing challenges that require specialized techniques and workstation tools to reveal their courses. The presented methods of evaluation of the vascular anatomy represent 2 years of experience with a quad-section CT scanner. No formal scientific study has, to our knowledge, proved which scanning technique is optimal.
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Technique Considerations for Multisection CT
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The parameters for the multisection CT protocol are dependent on the speed of the scanner, the section thickness options, the number of scanning phases (scanning timing relative to the administration of contrast medium), and the anatomic coverage of each scan. The phases that can be considered are precontrast, arterial, venous, nephrographic, and delayed. Precontrast scans are used to locate the kidneys, detect urolithiasis, and provide baseline attenuation measurements of renal masses. The optimal timing for the contrast-enhanced phases is dependent on the volume of contrast medium, the rate of its administration, and the subject’s cardiac output. The delay time refers to the difference between the start of contrast medium injection and the start of scanning. Arterial-phase scanning, performed to evaluate the arterial anatomy, is begun after a delay time of 15 seconds. The high rate of injection (5 mL/sec) necessitates the use of a shorter delay time for the arterial phase. Venous-phase scanning, performed to evaluate the venous anatomy, is begun after a delay of 40–50 seconds. The nephrographic phase refers to the time during which the renal cortex and medulla are uniformly enhanced and contrast medium has not yet entered the renal calices and pelvis. This phase is optimal for evaluation of the renal parenchyma and detection of focal masses that arise in the cortex or medulla. The phase is best visualized with a delay time of 75–100 seconds. The delayed phase, used to evaluate the collecting system, occurs with a delay time of 5 minutes or more. As an alternative, the collecting system and ureters may be evaluated with conventional radiography after CT.
Although a five-phase CT examination may be possible with a multisection CT scanner, there are reasons to restrict the number of phases. First and most important, we must limit the radiation dose to the subjects, who are generally healthy, young adults. Second, even multisection scanners have limitations, and there are trade-offs to be made among spatial resolution of the images (in all three planes), image noise, and scanning speed. Because of limitations in anode heat capacity, it is impossible to perform a five-phase, 1-mm-section-width examination and produce images with acceptable noise levels.
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Rationale and Procedures for Three-Phase Renal Evaluation
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As a compromise, to limit radiation dose, we use a three-phase CT examination followed with conventional radiography. Dedicated venous-phase scanning is not performed because the renal veins become enhanced quickly and are usually seen on arterial-phase scans. The gonadal and lumbar veins become enhanced more slowly and are seen well on nephrographic-phase scans. A section width of 1 mm is used for both the arterial- and nephrographic-phase examinations because accessory renal arteries and lumbar veins can be small and easily missed when thicker sections are used. Delayed-phase CT scans are not obtained because conventional radiography provides the same information at a lower radiation dose. Conventional radiography is required to depict ureteral anomalies and diseases such as medullary sponge kidney disease and papillary necrosis that cannot be diagnosed with CT. The total radiation dose for three-phase CT is about 7.7 rad, substantially less than that with the combination of angiography and excretory urography. The following imaging strategy is based on 2 years of experience with a quad-section CT scanner.
Phase 1: Precontrast
Scanning is performed from the top of the kidneys to the pubic symphysis without the use of contrast medium. The technical factors for the Mx8000 scanner (Marconi Medical Systems, Cleveland, Ohio) are shown in Table 1.
Phase 2: Arterial
An 18-gauge angiographic catheter is placed into a basilic vein or the brachial vein (with ultrasonographic guidance) at the elbow, and saline solution is administered. Nonionic contrast medium containing 300 mg of iodine per milliliter at a dose of 2 mL per kilogram of body weight (limit, 190 mL) is injected at 5 mL/sec. The delay time from the start of injection to the start of scanning is 15 seconds. A test bolus is not used. Scanning is performed from the top of the kidneys to 2 cm below the top of the iliac crest. The technical factors are shown in Table 1. In large subjects, a larger section width (2.5 mm) may be required to maintain acceptable levels of image noise. If a polar artery emerges from the lower part of the aorta or from the common iliac artery, the part of the artery near its origin will not be seen but the part near the kidney will be depicted. In the rare occurrence of this variant, repeated imaging may be necessary to fully evaluate the path of the vessel.
Phase 3: Nephrographic
The delay time from the start of injection to the start of scanning is 75 seconds. Scanning is performed in a fashion identical to that during the arterial phase.
Conventional Radiography
Conventional radiography of the abdomen and pelvis is performed 5 minutes after the CT examination (10 minutes after injection) with the subject in the supine position and the use of 65 kVp, narrow-latitude film, rare earth screens, and phototiming.
Postprocessing
All renal donor images are routinely sent to a workstation (MxView; Marconi Medical Systems). The postprocessing evaluation may include the use of the following techniques: multiplanar reformatting, maximum intensity projection, shaded surface display, and volume rendering (12). The postprocessing cannot be reduced to just one technique, since the various postprocessing methods have different advantages and shortcomings. The maximum intensity projection technique, for example, is excellent in bringing out high-attenuation, high-contrast, well-defined structures such as arteries, while multiplanar reformatting is the preferred technique for analysis of small, less well opacified veins.
"Image Load"
A complete evaluation usually contains more than 800 source images (precontrast phase, >200; arterial phase, >300; and venous phase, >300) and additional postprocessed images. Our data sets for the arterial and nephrographic phases are isotropic (1-mm spatial resolution in all planes), which provides tremendous flexibility for anatomic display. However, this "image load" may become a psychologic and logistic burden if it is not dealt with correctly (14). First, the bandwidth of the local network must be adequate to quickly transfer the large image volume from the scanner to the workstation. Second, the workstation should have at least 1 Gbyte of memory, and it should handle several large stacks of images simultaneously. The image load on the radiologic technologists, radiologists, and surgeons can be eased by not printing the source images. A limited number of pertinent images of the arterial and venous anatomy and any pathologic conditions can be created for the surgeon.
Measurements
Measurements of the vascular structures are performed on "curved-plane" multiplanar reformatted images. These measurements help the surgeons find the arteries and veins that we detected preoperatively. Most surgeons require at least 2 cm of renal artery before hilar branching to ensure adequate control and anastomosis.
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Evaluation of Potential Renal Donors
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Renal Stone Disease
When excretory urography and angiography were used to evaluate potential donors, no subject with urolithiasis was allowed to donate a kidney. With the excellent contrast resolution of CT, we have found that the prevalence of urolithiasis is much higher than previously reported, and we detect stones in many subjects who have never experienced symptoms or at least never had the diagnosis established. Because of the apparent increased prevalence of asymptomatic urolithiasis, some transplantation centers allow some asymptomatic, otherwise healthy subjects with urolithiasis to donate provided they have a low stone burden. One policy regarding renal stone disease permits donation with the provision that the subject is asymptomatic, is more than 40 years old, and has only one stone smaller than 8 mm in diameter or no more than three stones, all unilateral and each smaller than 3 mm in diameter (Fig 1). However, more restrictive policies exist for cases in which any depicted stone becomes an absolute contraindication to renal donation.
Evaluation of Arteries and Veins
In 70% of cases, single renal arteries exist bilaterally. In 30%, multiple renal arteries are present. Anatomic variants include supplementary arteries, polar arteries, and extrahilar branching. The number of arteries, their sizes, and the locations of their origins on the aorta determine whether the kidney is suitable for donation. The lengths of the arteries from their origins to the first bifurcation are measured. The arterial evaluations can be performed with maximum intensity projection (Fig 2), shaded surface display (Fig 3), or volume rendering (Fig 4). Arterial diseases such as renal arterial aneurysm (Fig 5) or renal arterial stenosis due to atherosclerosis or fibromuscular dysplasia can be detected.
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Figure 2a. Maximum intensity projection CT scans show accessory renal arterial variants: hilar artery to the left kidney (arrow in a), early branching to the right kidney (arrowheads in b) and polar artery to the left kidney (arrow in b), and multiple polar arteries to both kidneys (arrows in c).
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Figure 2b. Maximum intensity projection CT scans show accessory renal arterial variants: hilar artery to the left kidney (arrow in a), early branching to the right kidney (arrowheads in b) and polar artery to the left kidney (arrow in b), and multiple polar arteries to both kidneys (arrows in c).
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Figure 2c. Maximum intensity projection CT scans show accessory renal arterial variants: hilar artery to the left kidney (arrow in a), early branching to the right kidney (arrowheads in b) and polar artery to the left kidney (arrow in b), and multiple polar arteries to both kidneys (arrows in c).
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Figure 4a. Volume rendering software allows direct interactive adjustment of size, angulation, and thickness of the tissue volume (slab) under evaluation. The images show what happens to two 1-mm-wide polar arteries (arrows in a) when the slab is moved. When the slab is more ventral (a), one branch is partially out of view (arrowhead in a), but when the slab is moved dorsally (b), the more dorsally projecting polar artery comes into view (arrowhead in b). The more dorsal location of the slab in b is indicated by the visibility of a vertebra. (c) When the slab is tilted, the small arteries are seen as separate vessels (arrow) and can thus be evaluated individually.
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Figure 4b. Volume rendering software allows direct interactive adjustment of size, angulation, and thickness of the tissue volume (slab) under evaluation. The images show what happens to two 1-mm-wide polar arteries (arrows in a) when the slab is moved. When the slab is more ventral (a), one branch is partially out of view (arrowhead in a), but when the slab is moved dorsally (b), the more dorsally projecting polar artery comes into view (arrowhead in b). The more dorsal location of the slab in b is indicated by the visibility of a vertebra. (c) When the slab is tilted, the small arteries are seen as separate vessels (arrow) and can thus be evaluated individually.
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Figure 4c. Volume rendering software allows direct interactive adjustment of size, angulation, and thickness of the tissue volume (slab) under evaluation. The images show what happens to two 1-mm-wide polar arteries (arrows in a) when the slab is moved. When the slab is more ventral (a), one branch is partially out of view (arrowhead in a), but when the slab is moved dorsally (b), the more dorsally projecting polar artery comes into view (arrowhead in b). The more dorsal location of the slab in b is indicated by the visibility of a vertebra. (c) When the slab is tilted, the small arteries are seen as separate vessels (arrow) and can thus be evaluated individually.
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Figure 5. Exclusion of a potential renal donor from donor surgery due to a right renal arterial aneurysm (arrow). Curved coronal reformatted image demonstrates an aneurysm that is thrombotic and partially calcified.
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In 85% of people, there is a single right renal vein. In 86% of people, there is a single left preaortic renal branch often combined with several extrarenal branches. The location and number of gonadal, adrenal, and lumbar veins must be delineated (Fig 6). Venous variants include multiple veins, right-sided gonadal and adrenal veins entering into the renal vein, and left retroaortic, circumaortic, and partially duplicated veins (Figs 7–9). The relationships among the renal, lumbar, and gonadal veins may be varied. Because laparoscopic surgery is performed with a more limited view than is open surgery, the surgeon needs to be forewarned about any anomalies. This forewarning reduces the risk of accidental venous injuries and bleeding. The renal veins and tributaries that drain into them must be shown. Any veins that drain into the proximal 2 cm of the gonadal vein must also be reported because they may be included in the dissection (Fig 10).
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Figure 6a. Analysis of drainage into the renal veins. (a) Coronal reformatted CT image shows gonadal vein (arrow) entering the left renal vein from below. (b) Oblique coronal reformatted image shows the left adrenal vein (solid arrow) draining into the renal vein. The inferior mesenteric artery (open arrow) and adrenal gland (arrowheads) are also visible. (c) Axial reformatted image shows a left lumbar vein (arrow) entering dorsally into the renal vein.
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Figure 6b. Analysis of drainage into the renal veins. (a) Coronal reformatted CT image shows gonadal vein (arrow) entering the left renal vein from below. (b) Oblique coronal reformatted image shows the left adrenal vein (solid arrow) draining into the renal vein. The inferior mesenteric artery (open arrow) and adrenal gland (arrowheads) are also visible. (c) Axial reformatted image shows a left lumbar vein (arrow) entering dorsally into the renal vein.
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Figure 6c. Analysis of drainage into the renal veins. (a) Coronal reformatted CT image shows gonadal vein (arrow) entering the left renal vein from below. (b) Oblique coronal reformatted image shows the left adrenal vein (solid arrow) draining into the renal vein. The inferior mesenteric artery (open arrow) and adrenal gland (arrowheads) are also visible. (c) Axial reformatted image shows a left lumbar vein (arrow) entering dorsally into the renal vein.
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Figure 7a. (a) Volume-rendered image shows a duplicated renal vein (arrows) and a large gonadal vein (arrowheads). (b) Two oblique lines on the reference image denote the thickness and angulation of the volume evaluated in a. (c) Coronal reformatted image shows the split renal vein (arrows) and gonadal vein (arrowheads) in fine detail. (d) Photograph obtained during surgery shows the split of the renal vein (S) close to the renal hilum and the merger (M) medially. The entry of the wide gonadal vein (G) is also seen. The duplication of the renal vein was overlooked during the initial evaluation in which only axial images were reviewed.
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Figure 7b. (a) Volume-rendered image shows a duplicated renal vein (arrows) and a large gonadal vein (arrowheads). (b) Two oblique lines on the reference image denote the thickness and angulation of the volume evaluated in a. (c) Coronal reformatted image shows the split renal vein (arrows) and gonadal vein (arrowheads) in fine detail. (d) Photograph obtained during surgery shows the split of the renal vein (S) close to the renal hilum and the merger (M) medially. The entry of the wide gonadal vein (G) is also seen. The duplication of the renal vein was overlooked during the initial evaluation in which only axial images were reviewed.
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Figure 7c. (a) Volume-rendered image shows a duplicated renal vein (arrows) and a large gonadal vein (arrowheads). (b) Two oblique lines on the reference image denote the thickness and angulation of the volume evaluated in a. (c) Coronal reformatted image shows the split renal vein (arrows) and gonadal vein (arrowheads) in fine detail. (d) Photograph obtained during surgery shows the split of the renal vein (S) close to the renal hilum and the merger (M) medially. The entry of the wide gonadal vein (G) is also seen. The duplication of the renal vein was overlooked during the initial evaluation in which only axial images were reviewed.
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Figure 7d. (a) Volume-rendered image shows a duplicated renal vein (arrows) and a large gonadal vein (arrowheads). (b) Two oblique lines on the reference image denote the thickness and angulation of the volume evaluated in a. (c) Coronal reformatted image shows the split renal vein (arrows) and gonadal vein (arrowheads) in fine detail. (d) Photograph obtained during surgery shows the split of the renal vein (S) close to the renal hilum and the merger (M) medially. The entry of the wide gonadal vein (G) is also seen. The duplication of the renal vein was overlooked during the initial evaluation in which only axial images were reviewed.
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Figure 8a. Split left renal vein not detected prior to surgery. The split was discovered during laparoscopic nephrectomy. In retrospect, the split renal vein could be detected on the axial source images (arrows in a and b). The duplication could also be brought out with volume rendering (c). The techniques of maximum intensity projection, shaded surface display, and multiplanar reformatting did not adequately show the anomaly.
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Figure 8b. Split left renal vein not detected prior to surgery. The split was discovered during laparoscopic nephrectomy. In retrospect, the split renal vein could be detected on the axial source images (arrows in a and b). The duplication could also be brought out with volume rendering (c). The techniques of maximum intensity projection, shaded surface display, and multiplanar reformatting did not adequately show the anomaly.
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Figure 8c. Split left renal vein not detected prior to surgery. The split was discovered during laparoscopic nephrectomy. In retrospect, the split renal vein could be detected on the axial source images (arrows in a and b). The duplication could also be brought out with volume rendering (c). The techniques of maximum intensity projection, shaded surface display, and multiplanar reformatting did not adequately show the anomaly.
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Figure 9a. Circumaortic left renal vein shown with both shaded surface display and reformatting. The stair-step artifacts in the images result from the use of 3-mm instead of 1-mm collimation. A = aorta, G = gonadal vein, V = vena cava. (a) Shaded surface display image depicts the anomaly (arrows) on one image. (b, c) Due to the oblique courses of the renal vein branches, several reformatted images are needed to show the anteroaortic renal branch (open arrows in c) and the retroaortic renal vein (solid arrows in b). In this case, the anomaly could not be shown with the volume rendering technique. At our institution, a potential donor with a retroaortic or circumaortic vein may donate the kidney; however, the surgery must be open rather than laparoscopic.
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Figure 9b. Circumaortic left renal vein shown with both shaded surface display and reformatting. The stair-step artifacts in the images result from the use of 3-mm instead of 1-mm collimation. A = aorta, G = gonadal vein, V = vena cava. (a) Shaded surface display image depicts the anomaly (arrows) on one image. (b, c) Due to the oblique courses of the renal vein branches, several reformatted images are needed to show the anteroaortic renal branch (open arrows in c) and the retroaortic renal vein (solid arrows in b). In this case, the anomaly could not be shown with the volume rendering technique. At our institution, a potential donor with a retroaortic or circumaortic vein may donate the kidney; however, the surgery must be open rather than laparoscopic.
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Figure 9c. Circumaortic left renal vein shown with both shaded surface display and reformatting. The stair-step artifacts in the images result from the use of 3-mm instead of 1-mm collimation. A = aorta, G = gonadal vein, V = vena cava. (a) Shaded surface display image depicts the anomaly (arrows) on one image. (b, c) Due to the oblique courses of the renal vein branches, several reformatted images are needed to show the anteroaortic renal branch (open arrows in c) and the retroaortic renal vein (solid arrows in b). In this case, the anomaly could not be shown with the volume rendering technique. At our institution, a potential donor with a retroaortic or circumaortic vein may donate the kidney; however, the surgery must be open rather than laparoscopic.
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Figure 10a. Accessory veins draining into the proximal 2 cm of the gonadal vein. (a) Oblique coronal reformatted CT scan shows two small tributaries to the gonadal vein (G): one 5 mm below (arrowheads) and one 10 mm below (arrows) the renal vein. (b, c) The inflows of the two small tributaries into the gonadal vein are shown on axial CT scans obtained 5 mm (arrowhead in b) and 10 mm (arrow in c) below the renal vein. (d) Volume-rendered image shows the gonadal vein (G) but not the small contributory veins. The renal vein is split (S).
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Figure 10b. Accessory veins draining into the proximal 2 cm of the gonadal vein. (a) Oblique coronal reformatted CT scan shows two small tributaries to the gonadal vein (G): one 5 mm below (arrowheads) and one 10 mm below (arrows) the renal vein. (b, c) The inflows of the two small tributaries into the gonadal vein are shown on axial CT scans obtained 5 mm (arrowhead in b) and 10 mm (arrow in c) below the renal vein. (d) Volume-rendered image shows the gonadal vein (G) but not the small contributory veins. The renal vein is split (S).
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Figure 10c. Accessory veins draining into the proximal 2 cm of the gonadal vein. (a) Oblique coronal reformatted CT scan shows two small tributaries to the gonadal vein (G): one 5 mm below (arrowheads) and one 10 mm below (arrows) the renal vein. (b, c) The inflows of the two small tributaries into the gonadal vein are shown on axial CT scans obtained 5 mm (arrowhead in b) and 10 mm (arrow in c) below the renal vein. (d) Volume-rendered image shows the gonadal vein (G) but not the small contributory veins. The renal vein is split (S).
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Figure 10d. Accessory veins draining into the proximal 2 cm of the gonadal vein. (a) Oblique coronal reformatted CT scan shows two small tributaries to the gonadal vein (G): one 5 mm below (arrowheads) and one 10 mm below (arrows) the renal vein. (b, c) The inflows of the two small tributaries into the gonadal vein are shown on axial CT scans obtained 5 mm (arrowhead in b) and 10 mm (arrow in c) below the renal vein. (d) Volume-rendered image shows the gonadal vein (G) but not the small contributory veins. The renal vein is split (S).
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The larger veins can be evaluated with the volume rendering technique (Fig 11); however, to find all smaller veins, we believe that the multiplanar reformatting technique is best and should employ axial, coronal, sagittal, and oblique planes (Figs 12, 13). Retroperitoneal varices can be detected with this technique (Fig 14).
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Figure 11a. Volume rendering versus multiplanar oblique and curved reformatting in the detection of pathologic conditions and understanding of the three-dimensional relationships. Coronal (a) and axial (b) reformatted images show the relationships among the large renal pelvis (P), renal veins, and gonadal vein (arrow in a and c) as well as a coronal volume-rendered image does (c).
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Figure 11b. Volume rendering versus multiplanar oblique and curved reformatting in the detection of pathologic conditions and understanding of the three-dimensional relationships. Coronal (a) and axial (b) reformatted images show the relationships among the large renal pelvis (P), renal veins, and gonadal vein (arrow in a and c) as well as a coronal volume-rendered image does (c).
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Figure 11c. Volume rendering versus multiplanar oblique and curved reformatting in the detection of pathologic conditions and understanding of the three-dimensional relationships. Coronal (a) and axial (b) reformatted images show the relationships among the large renal pelvis (P), renal veins, and gonadal vein (arrow in a and c) as well as a coronal volume-rendered image does (c).
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Figure 12a. Accessory left renal vein and large left gonadal vein at reformatting. (a) Coronal reformatted image shows the accessory renal vein (curved arrow) merging into the gonadal vein (straight solid arrow) just beneath the point where the gonadal vein merges with the main renal vein (open arrow). (b) Photograph obtained during surgery helps confirm the findings at CT. Gonadal vein with surgical clip (short straight arrow), main renal vein (long straight arrow), and accessory renal vein (curved arrow) are evident. (c) Photograph obtained during surgery shows gonadal vein (straight arrow), lifted with a surgical instrument, immediately beneath the point where the accessory renal vein entered the gonadal vein. At this point, a 2-mm-wide vein was found (curved arrow). (d) Axial CT image obtained during the nephrographic phase shows that this small vein (arrow) could be depicted in retrospect.
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Figure 12b. Accessory left renal vein and large left gonadal vein at reformatting. (a) Coronal reformatted image shows the accessory renal vein (curved arrow) merging into the gonadal vein (straight solid arrow) just beneath the point where the gonadal vein merges with the main renal vein (open arrow). (b) Photograph obtained during surgery helps confirm the findings at CT. Gonadal vein with surgical clip (short straight arrow), main renal vein (long straight arrow), and accessory renal vein (curved arrow) are evident. (c) Photograph obtained during surgery shows gonadal vein (straight arrow), lifted with a surgical instrument, immediately beneath the point where the accessory renal vein entered the gonadal vein. At this point, a 2-mm-wide vein was found (curved arrow). (d) Axial CT image obtained during the nephrographic phase shows that this small vein (arrow) could be depicted in retrospect.
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Figure 12c. Accessory left renal vein and large left gonadal vein at reformatting. (a) Coronal reformatted image shows the accessory renal vein (curved arrow) merging into the gonadal vein (straight solid arrow) just beneath the point where the gonadal vein merges with the main renal vein (open arrow). (b) Photograph obtained during surgery helps confirm the findings at CT. Gonadal vein with surgical clip (short straight arrow), main renal vein (long straight arrow), and accessory renal vein (curved arrow) are evident. (c) Photograph obtained during surgery shows gonadal vein (straight arrow), lifted with a surgical instrument, immediately beneath the point where the accessory renal vein entered the gonadal vein. At this point, a 2-mm-wide vein was found (curved arrow). (d) Axial CT image obtained during the nephrographic phase shows that this small vein (arrow) could be depicted in retrospect.
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Figure 12d. Accessory left renal vein and large left gonadal vein at reformatting. (a) Coronal reformatted image shows the accessory renal vein (curved arrow) merging into the gonadal vein (straight solid arrow) just beneath the point where the gonadal vein merges with the main renal vein (open arrow). (b) Photograph obtained during surgery helps confirm the findings at CT. Gonadal vein with surgical clip (short straight arrow), main renal vein (long straight arrow), and accessory renal vein (curved arrow) are evident. (c) Photograph obtained during surgery shows gonadal vein (straight arrow), lifted with a surgical instrument, immediately beneath the point where the accessory renal vein entered the gonadal vein. At this point, a 2-mm-wide vein was found (curved arrow). (d) Axial CT image obtained during the nephrographic phase shows that this small vein (arrow) could be depicted in retrospect.
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Figure 13a. Value of thin-collimation multisection CT and multiplanar reformatting in the delineation of veins that merge into the renal vein. A = renal artery, Ad = adrenal vein, Ao = aorta, G = gonadal vein, IMV = inferior mesenteric vein, L = lumbar vein, N = lymph node, SMA = superior mesenteric artery, V = renal vein. (a, b) Axial (a) and sagittal (b) reformatted images best display the lumbar vein. (c) Oblique coronal reformatted image best depicts the merging renal veins. (d) Oblique sagittal reformatted image shows the paired gonadal veins.
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Figure 13b. Value of thin-collimation multisection CT and multiplanar reformatting in the delineation of veins that merge into the renal vein. A = renal artery, Ad = adrenal vein, Ao = aorta, G = gonadal vein, IMV = inferior mesenteric vein, L = lumbar vein, N = lymph node, SMA = superior mesenteric artery, V = renal vein. (a, b) Axial (a) and sagittal (b) reformatted images best display the lumbar vein. (c) Oblique coronal reformatted image best depicts the merging renal veins. (d) Oblique sagittal reformatted image shows the paired gonadal veins.
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Figure 13c. Value of thin-collimation multisection CT and multiplanar reformatting in the delineation of veins that merge into the renal vein. A = renal artery, Ad = adrenal vein, Ao = aorta, G = gonadal vein, IMV = inferior mesenteric vein, L = lumbar vein, N = lymph node, SMA = superior mesenteric artery, V = renal vein. (a, b) Axial (a) and sagittal (b) reformatted images best display the lumbar vein. (c) Oblique coronal reformatted image best depicts the merging renal veins. (d) Oblique sagittal reformatted image shows the paired gonadal veins.
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View larger version (159K):
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Figure 13d. Value of thin-collimation multisection CT and multiplanar reformatting in the delineation of veins that merge into the renal vein. A = renal artery, Ad = adrenal vein, Ao = aorta, G = gonadal vein, IMV = inferior mesenteric vein, L = lumbar vein, N = lymph node, SMA = superior mesenteric artery, V = renal vein. (a, b) Axial (a) and sagittal (b) reformatted images best display the lumbar vein. (c) Oblique coronal reformatted image best depicts the merging renal veins. (d) Oblique sagittal reformatted image shows the paired gonadal veins.
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Evaluation of Renal Parenchyma
The renal parenchyma is best evaluated at the nephrographic phase, which is used to detect diseases such as polycystic disease and renal cell carcinoma (13). Small isolated renal cysts are usually not contraindications to surgery.
Evaluation of the Collecting System and Ureters
Medullary sponge kidney disease and papillary necrosis are contraindications to renal donation, and these diseases cannot be detected with CT (although complications from these diseases can sometimes be detected). The best way to screen for these diseases is with conventional radiography performed 10 minutes after the CT examination. A CT scout view does not have adequate quality to substitute for a conventional radiograph. Conventional radiography allows depiction of duplication anomalies of the collecting system and ureters.
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Clinical Experience
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During the period January–October 2000, renal donor CT evaluation was performed in 52 subjects. Of the 52 subjects, 30 donated kidneys: 24 via laparoscopic surgery and six via open surgery. Surgery was not performed in 22 subjects. In 12 of the nondonors, CT showed pathologic processes or anatomic variations that excluded them from donation (renal cystic disease, n = 4; vascular variation, n = 1; renal stones, n = 6; and bladder calcifications, n = 1). In 10 subjects, the reasons for exclusion were unrelated to renal anatomy or pathologic conditions (improved renal status of recipient, n = 1; donor hypertension, n = 1; donor history of cancer, n = 1; recipient health problems, n = 1; and cross match incapability, n = 6). Of the 52 subjects, only 14 had completely normal findings at scanning. Twenty-seven had abnormal vascular anatomy (Table 2), 12 had abnormalities in their kidneys, and 12 had other findings such as liver or splenic lesions. In five subjects, the only abnormal finding was in the kidneys, and six had abnormal kidney findings and vascular variants.
Discovered during surgery were 12 vascular variants that had not been reported by the radiologist. Nine variants were venous (two left lumbar and two left adrenal veins, small posterior branches of the left renal vein, two left lumbar veins, one large left lumbar vein [n = 2], partially duplicated left renal vein, and multiple small retroperitoneal veins [n = 3]). Three variants were arterial (early left renal arterial bifurcation, superior left accessory renal artery, severe angulation of the left renal artery). One unexpected finding required that surgery be converted from laparoscopic to open. All of these variants, except one, were visible in retrospect on the CT images (either on axial source images or on reformatted images). Most errors were made early in our experience. All nine donor kidneys were successfully transplanted.
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Discussion
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In the past, when living renal donors underwent open surgical techniques, the radiologist needed to provide only information about the arterial anatomy and any pathologic processes. Now, the advent of laparoscopic nephrectomy has created a new challenge for radiologists: definition of the venous anatomy. Multisection CT allows definition of that anatomy and more. Multisection CT followed by conventional radiography provides a complete evaluation with much more information than was previously provided with excretory urography and angiography. It is much more sensitive in the detection of urolithiasis and diseases of the renal parenchyma. The CT examination is also less invasive and less costly.
There is a learning curve for radiologists, and perception errors are common during analysis of the venous system, at least early in one’s experience. Vascular variants are common (44 variants in 27 of 52 patients). Our errors prompted us to change the imaging technique to enhance the quality of the venous interpretation. Earlier, 2.5-mm section thickness was used. Now we try to use 1.0 mm for the nephrographic phase. Earlier, we also relied heavily on analysis of the axial images during evaluation of the veins. According to our experience, a "volume approach" is more beneficial. With the 1-mm scanning technique, isotropic viewing is possible. We believe that vessels passing in planes oblique to the axial plane are best evaluated with reformatted images. We had hoped that volume rendering would be the answer to all questions; however, this has not been the case. We have found it necessary to learn the anatomy as viewed in coronal, sagittal, and oblique planes, and for that the multiplanar reformatting technique is essential.
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References
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|---|
-
Ratner LE, Cisek L, Moore R, Cigarroa F, Kaufman H, Kavoussi LR. Laparoscopic live donor nephrectomy. Transplantation 1995; 60:1047-1049.[Medline]
-
Ratner LE, Kavoussi L, Sroka M, et al. Laparoscopic assisted live donor nephrectomy: compari-son with the open approach. Transplantation 1997; 63:229-233.[Medline]
-
Sasaki TM, Finelli F, Burgarin E, et al. Is laparoscopic donor nephrectomy the new criterion standard?. Arch Surg 2000; 135:943-947.[Abstract/Free Full Text]
-
Leventhal JR, Deeik RK, Joehl RJ, et al. Laparoscopic live donor nephrectomy: is it safe?. Transplantation 2000; 70:602-606.[Medline]
-
Rubin GD, Alfrey EJ, Dake MD, et al. Assessment of living renal donors with spiral CT. Radiology 1995; 195:457-462.[Abstract/Free Full Text]
-
Cochran ST, Krasny RM, Danovitch GM, et al. Helical CT angiography for examination of living renal donors. AJR 1997; 168:1569-1573.[Abstract/Free Full Text]
-
Smith PA, Ratner LE, Lynch FC, Corl FM, Fishman EK. Role of CT angiography in the preoperative evaluation for laparoscopic nephrectomy. RadioGraphics 1988; 18:589-601.[Abstract]
-
Pozniak MA, Balison DJ, Lee FT, Tambeaux RH, Uehling DT, Moon TD. CT angiography of potential renal transplant donors. RadioGraphics 1998; 18:565-587.[Abstract]
-
Del Pizzo JJ, Sklar GN, You-Cheong JW, Levin B, Krebs T, Jacobs SC. Helical computerized tomography arteriography for evaluation of live renal donors undergoing laparoscopic nephrectomy. J Urol 1999; 162:31-34.[Medline]
-
Platt JF, Ellis JH, Korobkin M, Reige KA, Konnak JW. Potential renal donors: comparison of conventional imaging with helical CT. Radiology 1996; 198:419-423.[Abstract/Free Full Text]
-
Platt JF, Ellis JH, Korobkin M, Reige K. Helical CT evaluation of potential kidney donors: findings in 154 subjects. AJR 1997; 169:1325-1330.[Abstract/Free Full Text]
-
Young GS, Silverman SG, Kattenbach J, et al. Three-dimensional computed tomography for planning urologic surgery. Urol Clin North Am 1998; 25:103-111.[Medline]
-
Kopka L, Fischer U, Zoeller G, Schmidt C, Ringert RH, Grabbe E. Dual-phase helical CT of the kidney: value of the corticomedullary and nephrographic phase for evaluation of renal lesions and preoperative staging of renal cell carcinoma. AJR 1997; 169:1573-1578.[Abstract/Free Full Text]
-
Rydberg J, Buckwalter KA, Caldemeyer KS, et al. Multisection CT: scanning techniques and clinical applications. RadioGraphics 2000; 20:1787-1806.[Abstract/Free Full Text]
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Abstract
LEARNING OBJECTIVES FOR TEST...
