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Turkish Society of Radiology 2011

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Multidetector computed tomography angiography (MDCTA)plays an increasingly important role in the evaluation of therenal vasculature (1). Although conventional angiography is

still regarded as the gold standard in renal vascular imaging, MDCTAis increasingly used as it is less invasive, easily applicable and available(24). MDCTA enables precise visualization of the normal and variantanatomy of several regions including the renal vasculature (57); howev-er, the main drawbacks of MDCTA are the exposure to ionizing radiationand the use of potentially nephrotoxic iodinated contrast material. Assuch, its use is limited in children and pregnant women and in patientswith impaired renal function.

Main clinical indications for renal MDCTA include the imaging work-up for ruling out renovascular hypertension, renal transplant recipientand donor evaluation, acute onset flank pain in patients with coagulat-ive disorders, direct renal trauma, arteriovenous communications, re-nal artery aneurysm, renal parenchymal or vascular calcifications, renalmanifestations of a systemic disease (e.g., vasculitis, thromboembolicdisease) (8).

Technical considerations

Image acquisiton

Diagnostic accuracy of renal MDCTA depends on the qualityof initialraw data acquired during the study. Adequate patient preparation, po-sitioning, as well as the proper contrast material injection, are of para-mount importance. CT protocol for the evaluation of the renal vascula-tureconsists of both unenhanced and enhancedCT scans. Unenhanced

scans of the kidneys and adrenal glands with contiguous sections of 3-mm thickness are necessary for the evaluation of adrenal lesions, vascu-lar calcifications, and renal calculi (Fig. 1).

Theoptimal anatomic coverage for the arterial phase scan, that is theprincipal part of the renal MDCT angiography, should include the re-gion between the celiac artery and terminal part of the common iliacarteries(Fig. 2). However, in patients with ectopic or transplanted kid-ney, the coverage can be modified; for this purpose careful preprocedur-al evaluation of the patient including medical records should be done.Slices with a thickness of 11.5 mm are obtained after rapid injection ofa 100-mL bolus of 300400 mg/mLnon-ionic iodinated contrast at a rateof 4 mL/s and a 70-mL bolus at a rate of 56 mL/s in 16 and 64-channelMDCT scanners, respectively. The scanning parameters are summarizedin Table. Image acquisiton is initiated after a 45 s and 67 s delay in 16and 64-channel MDCT scanners, respectively, when the threshold en-hancement of 100 HU is reached within the region of interest placed onthe abdominal aorta. For the evaluation of renal venous structures andabdominal viscera whole abdomen is scanned with a section thickness

CARDIOVASCULAR IMAGING

PICTORIAL ESSAY

CT angiography of the renal arteries and veins: normal anatomyand variants

Tuncay Hazrolan, Meryem z, BarTrkbey, Ali Devrim Karaosmanolu, Berna Sayan Ouz,Murat Canyiit

From the Department of Radiology ([email protected]), Hacettepe University School of Medicine, Ankara, Turkey.

Received 17 June 2009; revision requested 20 July 2009; revision received25 July 2009; accepted 30 July 2009.

Published online 9 February 2010DOI 10.4261/1305-3825.DIR.2902-09.1

ABSTRACTConventional angiography has long been regarded as goldstandard imaging modality for evaluation of the renal vascu-lature. Introduction of multidetector computed tomography(MDCT) angiography had a groundbreaking impact on evalu-ation of the renal vessels and is gradually replacing conven-

tional angiography as standard imaging. Herein, we reviewand illustrate the normal and variant anatomy of renal vesselswith special emphasis on imaging protocols and reconstruc-tion techniques in MDCT.

Key words: computed tomography, X-ray angiography renal artery renal vein

Diagn Interv Radiol 2011; 17:6773


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rolan et al.68 March 2011 Diagnostic and Interventional Radiology

of 5 mm. Ultimately, in renal trans-plant donors, 710 min delayed scansare obtained for the evaluation of theureters.

Postprocessing techniques

Axial source images remain the basisfor diagnosis; however, postprocessed2D and 3D reformations contribute

significantly for accurate evaluation.Most commonly used post-processingtechniques are multiplanar and curvedplanar reformations (MPR and CPR),maximum intensity projection (MIP),and volume rendering (VR).

MIP images provide angiography-like images with an excellent overviewof vascular anatomy and their variableprojection angles should be used forthe accurate interpretation of stenoticlesions. MPR and CPR images are par-ticularly useful for correct evaluationof the arterial luminal diameter foraccurate depiction and quantificationof the arterial stenosis. VR images canbe used for the overall display of theabdominal vasculature and can pro-vide an insight for the interpreter andreferring physicians (5, 9). Finally, theaxial source images should always bereviewed for possible presence of an ac-companying non-vascular pathology.

Normal renal vascular anatomy

In the majority of the human sub-jects, each kidney is supplied by one

renal artery arising from the abdomi-nal aorta, but in approximately 30%of individuals more than one arterycan be present (10). Renal arteriesare usually 46 cm in length and 56mm in diameter. They typically arisefrom the aorta at the levelof L1L2 in-tervertebral disk space below the ori-gin of the superior mesenteric artery(SMA), and tend to course through theanterior portion of the renal pelvis.Both renal arteries usually course in aslightlyposterior direction due to theanatomic orientation of the kidneys.The right renal artery orifice is locatedon the anterolateral wall of the aorta.The left renal artery originates in amore lateral location. The right renal

artery characteristically courses down-wards toward the right kidney behindthe inferiorvena cava (IVC), while theleft has a more horizontal, upwardorientation posterior to the left renalvein (Fig. 3). Each renal artery sup-plies the inferior adrenal artery. Theinferior adrenal arteries arise directly

Figure 1. Non-contrast scanning areaincludes the adrenal glands and kidneys.These images provide important informationabout the focal lesions of the adrenal gland,

renal stones, and vessel wall calcifications.

Figure 2. Scanning area of the arterial phaseshould include the abdominal aorta andcommon iliac arteries, where the main andaccessory renal arteries originate.

Figure 3.Volume rendering image demonstrates the normal anatomy of the renal arteries(arrows). The renal arteries typically arise from the aorta at the levelof L1L2 intervertebral diskspace below the origin of the SMA (arrowhead).

Table. MDCT scanning parameters used in renal CT angiography

16 MDCT 64 MDCT

Unenhanced Arterial Venous Unenhanced Arterial VenousKV/effective mAs 120/140 140/140 120/140 120/160 120/150 120/160

Rotation time (s) 0.5 0.5 0.5 0.5 0.33 0.5

Detector collimation (mm) 1.5 0.75 1.5 1.2 0.6 1.2

Slice thickness (mm) 3 1 5 3 1 5

Pitch 1.25 1.5 1.25 1.4 1.4 1.4

Reconstruction interval 3 1 5 3 0.5 5

Scan delay (s) 0 45 60 0 78 60

Dose-length product(DLP) (mGy cm)

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CT angiography of the renal arteries and vei ns 69Volume 17 Issue 1

from the proximal renal artery in two-thirds of people and they may be soli-tary or multiple (11). The main renalartery then continues before dividinginto four anterior branches at the re-nal hilum: the apical, upper, middle,and lower anterior segmental arteries(Fig. 4). The segmental arteries then

course through the renal sinus andbranch into the lobar arteries givingone branch to each pyramid. Furtherdivisions include the interlobar, arcu-ate, and interlobular arteries.

Renal veins course anterior to therenal arteries. The renal cortex isdrained sequentially by the inter-

lobular, arcuate, interlobar, and lobarveins, and then they converge to formthe main renal vein. The left renalvein normally courses between theSMA and aorta before draining intothe medial aspect of the IVC, whereasthe right drains into the lateral aspectof the IVC (Fig. 5) (12).

Figure 4.a, b.Coronal volumerendering images show anterior(a)and posterior (b)views ofnormal segmental anatomyof the renal artery. The firstdivision is the posterior branch(arrowhead).The posteriorbranch gives two segmentalbranches (black arrows),supplying the posterior central

portion of the kidney. The mainrenal artery then continues itscourse before branching intofour anterior branches (arrows)at the renal hilum.

ba

Figure 5.a, b.Coronal (a)and axial (b)volume renderingimages show the normal renal vein anatomy. The renal veins(arrows)course anterior to the renal arteries (arrowheads). The leftrenal vein normally courses between the SMA (thin arrow) and the

aorta (small asterisk)before draining into the medial aspect of theIVC (big asterisk),while the right vein drains to the lateral aspectof the IVC.

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Sensitivity of CT angiography in

demonstration of the course of mainrenal arteries and veins is around100%. Accurate depiction of the re-nal vessels is of paramount impor-tance for potential kidney donors,especially on the left, as it is oftenthe preferred side for renal harvest-ing (13).

Renal vascular variations

Renal artery variations

Anatomic variations of the renal ar-teries are common in general popula-

tion with different frequencies amongseveral ethnic and racial groups (14).These variations are becoming moreimportant considering the gradual in-crease in the number of interventionalradiological procedures, as well as uro-logical-vascular operations and trans-plantations (15).

Accessory renal arteries constitutethe most common and clinically im-portant renal arterial variations andcan be seen in up to one-thirdof thenormal population. Accessory arter-ies usually arise from the aorta or iliac

arteries at any level between T11 andL4. Typically, the accessory renal ar-tery courses into the renal hilum toperfuse the upper or lower renal poles.They may also enter the renal paren-chyma directly from the renal cortex,whereupon it may also be termed thepolar artery (Fig. 6). Rarely,they mayarise from the lower thoracic aorta

(Fig. 7), as well as from the lumbarand mesenteric arteries (16). VR, MIP

and MPR images may accurately dem-onstrate accessory arteries. Rubin etal. showed 3D CT angiography to be100% sensitive in thevisualization ofaccessory renal arteries (17, 18).

Prehilarbranchingis another commonvariant that can be readily detectedwith 3D imaging. This variant is partic-ularly important for the preoperativemapping of the renal transplant do-nors. Theoretically, it is the branchingof the main renal arteries into segmen-tal branches at a more proximal levelthan the renal hilum (Fig. 8)(18).

Rarely, renal arteries may originatefrom the more proximal portion ofthe abdominal aorta above the originof the SMA. Aberrant renal arteriesmay even originate from the iliac ar-teries in rare cases; however, they canbe more common in ectopic kidneys(Fig. 9).

In the case of horse-shoe kidney, themain renal arteries develop normally;

Figure 6.Volume rendering image shows the main renalarteries (thin arrows) and accessory renal arteries. Theaccessory arteries usually arise from the aorta or iliac arteries,between the levels of T11 and L4. The accessory renal artery(arrowheads)coursesinto the renal hilum. The polar arteries,a subgroup of accessory renal arteries, enter the renalparenchyma directly from the renal cortex (thick arrows).

Figure 7. Coronal MPR image shows a rare origin of the accessory renal artery(arrow) which is from the distal part of the thoracic aorta. The main renalartery (arrowhead) emerges at the usual level of the abdominal aorta. Calcificatherosclerotic plaques are seen in the distal parts of both the main andaccessory renal arteries (thin arrows).

Figure 8.Volume renderingimage shows prehilarbranching(arrow)of the right renal artery(arrowhead).In this variation, therenal arteries give the segmentalrenal branches at a moreproximal level than the renalhilum. This variant is particularlyimportant for the preoperativemapping of the renal donors.


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however, the mesenephric and me-tanephric arteries often persist to sup-ply the upper and lower poles, respec-tively. These primitive arteries mayarise at different levels in the aorta andiliac arteries (19).

Renal vein variations

The most common venous variantis the presence of supernumerary renalveins

which can be seen in approxi-mately 1530% of individuals (16),and occasionally the accessory renal

veinthat can drain into the iliac vein(Fig. 10).

Circumaortic renal vein is anothervariant in which the left renal vein bi-furcates into ventraland dorsal limbsenclosing the abdominal aorta (20).

Figure 9.Volume rendering image shows aberrant renal arteries (arrows) ofa pelvic kidney. Two of them originate from the left main iliac artery and thethird one from the terminal aorta.

Figure 10.ad.Coronal oblique multiplanar reconstruction (a)and axial images (bd)show supernumerary renal veins. There are three renalveins of the left kidney. The superior renal vein (thick arrow) is located at its usual level and drains into the IVC. The middle renal vein (thinarrow) courses between the aorta and vertebral column (retroaortic renal vein) and drains into the terminalpart of the IVC. The inferior renalvein (arrowhead)drains into the left iliac vein.

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The retroaortic portion is located in amore caudal position with respect tothe preaortic one. It has a 2.48.7%prevalence and is particularly impor-tant in kidney transplant donors (Fig.11) (21).

Retroaortic renal vein is a less com-mon venous anomaly which can bedetected in 3% of individuals. In thisvariant, theleft renal vein courses pos-terior to the aorta and drains intothelower lumbar portion of the inferiorvena cava (Fig. 12) (20).

Variations of the renal veins andIVC occur infrequently but if theyremain unidentified in potential sur-gery candidates, that may increasesurgical morbidity during operations,therefore it is necessary to evaluaterenal veins and azygocaval anatomycorrectly (22). Knowing the above-

mentioned renal venous variationsalso carries importance when place-ment of an inferior vena cava filter isconsidered.

Conclusion

Conventional angiography is tradi-tionally regarded as the gold standardimaging modality for evaluation of therenal vasculature. However, MDCTAenables less invasive, accurate, promptand effective visualization of the re-nal vessels. MDCTA, together withreformatting techniques, can providevaluable information about not onlyintraluminal pathologies but also theanatomical variations including thenumber, size, course, and anatomy ofthe renal vasculature.

References

1. Bluemke DA, Cambers TP. Spiral CT an-giography: an alternative to conventionalangiography. Radiology 1995;195:317319.

2. Prokop M. Multislice CT angiography. EurJ Radiol 2000; 36:8696.

3. Rubin GD, Shiau MC, Schmidt AJ, et al.Computed tomographic angiography: his-torical perspective and new state of the art

using multi detector row helical comput-ed tomography. J Comput Assist Tomogr1999; 23:8390.

4. Toprak U, Erdoan A, Glbay M, KarademirMA, Paaolu E, Akar OE. Preoperativeevaluation of renal anatomy and renalmasses with helical CT, 3D-CT and 3D-CTangiography. Diagn Interv Radiol 2005;11:3540.

5. Urban BA, Ratner LE, Fishman EK.Three-dimensional volume-rendered CT angiog-raphy of the renal arteries and veins: nor-mal anatomy, variants, and clinical appli-cations. Radiographics2001; 21:373386.

Figure 11.Axial volume rendering image shows a circumaortic renalvein. The left renal vein (thin arrow)bifurcates into ventral (thick arrow)

and dorsal (arrowhead) limbs that enclose the abdominal aorta.

Figure 12.a, b.Axial thin MIP (a), volume rendering (b)images show a retroaortic renal vein. The left renal vein passes (arrow)posterior to theaorta (arrowhead) and drains intothe lower part of the IVC (asterisk).

ba


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6. Trkvatan A, Ozdemir M, Cumhur T, OlerT. Multidetector CT angiography of renalvasculature: normal anatomy and variants.Eur Radiol 2009; 19:236244.

7. Ozkan U, Ouzkurt L, Tercan F, KizilkiliO, Ko Z, Koca N.Renal artery origins andvariations: angiographic evaluation of 855consecutive patients. Diagn Interv Radiol2006;12:183186.

8. Kawashima A, Sandler CM, Ernst RD,Tamm EP, Goldman SM, Fishman EK.

CT evaluation of renovascular disease.Radiographics 2000; 20:13211340.

9. Fleischmann D. Multiple detector-row CTangiography of the renal and mesentericvessels. Eur J Radiol 2003; 45:7987.

10. Leung DA, Hagspiel KD, Angle JF, et al. MRangiography of the renal arteries. RadiolClin North Am 2002; 40:847865.

11. Kawamoto S, Montgomery RA, Lawler LP,Horton KM, Fishman EK. Multi-detec-tor row CT evaluation of living renal do-nors prior to laparoscopic nephrectomy.Radiographics 2004; 24:453466.

12. El-Galley RES, Keane TE. Embryology,anatomy, and surgical applications of thekidney and ureter. Surg Clin North Am2000; 80:381401.

13. Smith PA, Ratner LE, Lynch FC, Corl FM,Fishman EK. Role of CT angiography inthe preoperative evaluation for laparo-scopic nephrectomy. Radiographics 1998;18:589601.

14. Boijsen E. Renal angiography: techniquesand hazards; anatomic and physiologic

considerations. In: Baum S, ed. Abramsangiography. 4th ed. Philadelphia: Little,Brown and Company, 1997; 11011131.

15. Khamanarong K, Prachaney P,Utraravichien A, Tong-Un T, SripaorayaK. Anatomy of renal arterial supply. ClinAnat 2004; 17:334336.

16. Kadir S. Angiography of the kidneys.In: Kadir S, ed. Diagnostic angiography.Philadelphia: Saunders, 1986; 445495.

17. Johnson PT, Halpern EJ, Kuszyk BS, et al.Renal artery stenosis: CT angiography-comparison of real-time volume renderingand maximum intensity projection algo-rithms. Radiology 1999; 211:337343.

18. Rubin GD, Alfrey EJ, Dake MD, et al.Assessment of living renal donors with spi-ral CT. Radiology 1995; 195:457462.

19. Cocheteux B, Mounier-Vehier C, GaxotteV, McFadden EP, Francke JP, Beregi JP. Rarevariations in renal anatomy and bloodsupply: CT appearances and embryologicalbackground. A pictorial essay. Eur Radiol2001; 11:779786.

20. Kahn PC. Selective venography of thebranches In: Ferris EJ, Hipona FA, Kahn

PC, et al. eds. Venography of the inferiorvena cava and its branches. Huntington:Krieger, 1973; 154224.

21. Minniti S, Visentini S, Procacci C.Congenital anomalies of the venae cavae:embryological origin, imaging features andreport of three new variants. Eur Radiol2002; 12:20402055.

22. Mathews R, Smith PA, Fishman EK,Marshall FF. Anomalies of the inferiorvena cava and renal veins: embryologicand surgical considerations.Urology 1999;53:873880.

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