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Comprehensive Evaluation of Patients with Suspected Renal Hypertension Using MDCT: From Protocol to Interpretation

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region from the diaphragm to the iliac arter-ies [1, 2] to cover all the potential origins of the accessory renal arteries [6, 7] (Fig. 1). The thinnest collimation and reconstruction thickness (range, 0.5–0.75 mm, according to the type of scanner) should be used to pro-vide detailed volumetric data.

A contrast medium volume of 1.3 mL/kg of body weight was injected intravenously and followed by a 30-mL saline chaser. No oral contrast medium was given. A bolus-tracking technique was used to synchronize scanning and contrast injection with a region of interest in the abdominal aorta. The flow rate was determined by the contrast-cover-ing time concept to obtain high and homo-geneous enhancement [8, 9]. For a detailed description of contrast-covering time, please refer to the associated references [8, 9]. The flow rate could be determined by the follow-ing equation:

contrast volume / flow rate = postthreshold delay + scan time + safe margin Flow rate = 1.3 mL/kg × body weight /

(7 seconds + scan time + 5 seconds) = 1.3 mL/kg × body weight /

(scan time + 12 seconds)

For parenchymal phase imaging, we used a low-dose protocol 4 minutes after contrast

Comprehensive Evaluation of

Patients with Suspected Renal

Hypertension Using MDCT: From

Protocol to Interpretation

I-Chen Tsai

1, 2

Min-Chi Chen

1,3

Wen-Lieng Lee

2,4

Pao-Chun Lin

1,3

I-Tzun Tsai

5

Wan-Chun Liao

1,3

Clayton Chi-Chang Chen

1,3

Tsai IC, Chen MC, Lee WL, et al.

1Department of Radiology, Taichung Veterans General Hospital, No. 160, Sec. 3, Taichung Harbor Rd., Taichung 407, Taiwan, ROC. Address correspondence to I. C. Tsai (sillyduck.radiology@gmail.com).

2Institute of Clinical Medicine and Cardiovascular Research Center, National Yang-Ming University, Taipei, Taiwan.

3Department of Radiological Technology, Central Taiwan University of Science and Technology, Taichung, Taiwan. 4Cardiovascular Center, Taichung Veterans General Hospital, Taichung, Taiwan.

5Department of Orthopedic Surgery, China Medical University Hospital, Taichung, Taiwan.

WEB

This is a Web exclusive article.

AJR 2009; 192:W245–W254

0361–803X/09/1925–W245 © American Roentgen Ray Society

F

or several years, MDCT has been widely used in many cardiovas-cular applications because of its robust spatial resolution. Many studies have confirmed the accuracy of MDCT in evaluating renal artery stenosis [1, 2]. Because its spatial resolution is superior to that of MRI and its acquisition time is shorter, MDCT is now widely used in clini-cal practice to survey patients with suspected renal hypertension except those contraindi-cated for iodinated contrast medium or ion-izing radiation. Radiologists should evaluate not only the renal arteries but also the whole scanned region including the renal parenchy-ma and adrenal glands because important in-cidental findings of diseases that present as hypertension could be detected [3–5]. In this article, we will use many illustrations to re-view the concept of a comprehensive evalua-tion of patients with suspected renal hyper-tension using MDCT.

Techniques

All of the patients described in this ar-ticle were imaged using a 40-MDCT scan-ner (Brilliance 40, Philips Healthcare). Any MDCT scanner with submillimeter collima-tion could theoretically achieve the same re-sults. The arterial phase scan included the Keywords: abdominal imaging, adrenal glands, CT,

kidneys, radiation dose, renal artery stenosis, renal hypertension

DOI:10.2214/AJR.08.1355

Received June 5, 2008; accepted after revision September 15, 2008.

OBJECTIVE. The objectives of this article are to, first, describe the reasons for and de-tails of the MDCT protocol for patients with suspected renal hypertension; second, explain the importance of comprehensive evaluation by MDCT in patients with suspected renal hy-pertension; third, review the image appearances of important conditions that may be encoun-tered in the reader’s clinical practice; and, fourth, explain what information should be includ-ed in a comprehensive MDCT report for patients with suspectinclud-ed renal hypertension.

CONCLUSION. MDCT is widely used for renal artery evaluation in patients with resis-tant hypertension. Because the regions outside the renal arteries might also have diseases that contribute to the symptoms, a comprehensive interpretation including the renal arteries, renal parenchyma, adrenal glands, and scanned abdomen is very important. The scanning param-eters should be adjusted according to the patient’s body habitus because some patients with suspected renal hypertension are children or young women. In this article, cases with illustra-tions showing the process from protocol to interpretation are provided.

Tsai et al.

MDCT of Patients with Suspected Renal Hypertension Vascular and Interventional Radiology

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injection (Fig. 1). The scan covered only the bilateral renal parenchyma. A low-kilovolt-age technique was used to provide a lower radiation dose but maintain acceptable im-age quality [10]. For the radiation control of scanning for both phases, we adjusted the ra-diation parameters according to the abdom-inal lateral width at the kidney level (Fig. 1 and Table 1). The automatic online dose modulation option provided by the scanner was also turned on.

The reason for obtaining parenchymal phase images is to visualize parenchymal diseases that are reported to be related to hypertension, including renal cell carcino-ma [11], renal stone [12], and renin-secret-ing tumor [3, 4]. Evaluation of the renal pa-renchyma is easier in the papa-renchymal phase because of homogeneous enhancement be-tween the renal cortex and medulla.

In patients in whom renal hypertension is suspected, ischemic nephropathy might have already developed [13]; therefore, cal-culating the estimated glomerular filtration rate (GFR) before scanning is critically im-portant to avoid renal failure. For patients with an estimated GFR of between 30 and 59 mL/min, especially those with other risk factors such as diabetes mellitus, isoosmolar contrast medium should be used to prevent contrast-induced acute kidney injury. For pa-tients with an estimated GFR of less than 30 mL/min, nephrology consultation is suggest-ed before scanning. If MDCT is still neces-sary, dialysis before and after the procedure is suggested [14].

Adjusting the radiation dose according to the patient’s body habitus is a recent trend [15]. In patients with suspected renal artery stenosis, minimizing radiation dose is impor-tant because many of these patients are chil-dren or young women who are sensitive to radiation. Adjusting scanning parameters ac-cording to the patient’s lateral width (Fig. 1) is based on the concept of the half-value layer [16]. The suggested radiation table was cre-ated and modified according to the recom-mendations of the American Association of Physicists in Medicine [16] and our clinical experience (Table 1). The tube current is dis-played as milliampere-seconds per section to adjust for the pitch and rotation time to make it easier to apply in different scanners.

Because the renal arteries and adrenal glands are small structures with 3D config-uration, we suggest that radiologists use a CT work station that can interactively dis-play any plane and thickness and that allows

postprocessing techniques for interpretation. Axial thin- or thick-section images, maxi-mum-intensity-projection techniques, and volume-rendering techniques should be used interchangeably and complementarily to pro-vide a complete evaluation [17, 18] (Fig. 1). Renal Artery Evaluation

Renal Artery Stenosis

Atherosclerosis—Atherosclerosis is the most common cause of renal artery steno-sis [13]. These stenoses are usually seen in the ostium or the proximal third of the re-nal arteries (Fig. 2). Plaque, which can be soft, calcified, or mixed in composition, is always observed. Because of MDCT’s high spatial resolution, the plaque can be easily quantified to determine whether the patient should receive endovascular intervention. The criterion of “significant stenosis” varies in different studies and among institutions, reflecting controversy about the indications for endovascular revascularization [13]. Our criterion is that a stenosis of more than 70% of the artery’s diameter should be con-sidered for endovascular revascularization if the patient has a compatible clinical his-tory [13].

Fibromuscular dysplasia—Fibromuscular dysplasia, the second most common cause for renal artery stenosis, is usually seen in young women (< 50 years old) [13]. The stenoses are usually found in the proximal or middle por-tion of the renal arteries (Fig. 3). A string-of-beads appearance, which indicates successive aneurysms and luminal stenoses, is the diag-nostic feature. These patients are good candi-dates for endovascular intervention because of their excellent prognosis after the proce-dure [13]. MDCT is an important technique in identifying patients who will benefit from intervention [19].

Follow-up after stenting—After stent place-ment, MDCT can be a great follow-up tool [18] because it is probably the only noninva-sive technique capable of directly visualizing the intrastent lumen with high spatial resolu-tion (Fig. 4). These patients usually present with recurrent hypertension or decreased re-nal size after rere-nal artery stenting.

Renal Artery Thromboembolism with Infarction

In some patients, the rapid development of resistant hypertension presents with de-creasing renal function and even flank pain [20]. These findings should raise the possi-TABLE 1: Radiation Table With CT Parameters Adjusted According to

Patient’s Abdominal Lateral Width at the Level of the Kidneys Lateral Width

(cm)

Arterial Phasea Delayed Phaseb

Tube Voltage

(kV) Effective mAs (mAs/slice) CTDI(mGy)vol Tube Voltage (kV) Effective mAs (mAs/slice) CTDI(mGy)vol

20.0–21.9 120 85 6.0 80 170 3.6 22.0–23.9 120 95 6.7 80 190 4.1 24.0–25.9 120 105 7.4 80 210 4.5 26.0–27.9 120 115 8.5 80 230 4.9 28.0–29.9 120 125 8.8 80 250 5.4 30.0–31.9 120 150 10.5 80 300 6.4 32.0–33.9 120 175 12.3 80 350 7.5 34.0–35.9 120 200 14.0 80 400 8.6 36.0–37.9 120 225 15.8 80 450 9.6 38.0–39.9 120 250 17.5 80 500 10.7 40.0–41.9 120 300 21.0 120 185 12.9 42.0–43.9 120 350 24.5 120 215 15.0 44.0–45.9 120 400 28.0 120 245 17.1 46.0–47.9 140 305 31.5 120 275 19.3 48.0–49.9 140 335 35.0 120 310 21.4

Note—CTDIvol = volumetric CT dose index.

aArterial phase was performed with a rotation time of 0.5 second, pitch of 0.676, slice thickness of 0.67 mm, and index of 0.33 mm.

bDelayed phase was performed with a rotation time of 1.0 second, pitch of 0.676, slice thickness of 0.8 mm, and index of 0.4 mm.

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bility of acute thromboembolism. The extent of thromboembolism can be evaluated in the renal arteries (Fig. 5). The enhancement of the renal parenchyma can also be assessed to determine the viability of the kidneys [20] (Fig. 5). Because the disease is uncommon, there is no guideline for therapy. Several case series in the literature that used intraar-terial local infusion of a thrombolytic agent achieved good results [21, 22].

Facilitating Endovascular Intervention MDCT can provide general information about the aorta, such as whether an abdominal aneurysm, a dissection, or ulcerative plaques are present that might complicate the inter-ventional procedure for interinter-ventional radiolo-gists and cardioloradiolo-gists. In addition, the follow-ing points should also be carefully checked.

Accessory Renal Arteries

The accessory renal arteries have origins distant from both kidneys; sometimes they can even arise from the iliac arteries [6, 7]. The accessory arteries should be identified and completely evaluated because stenosis in these arteries can also cause renal hyperten-sion (Fig. 6). If these arteries are not identi-fied, the diagnosis could be delayed because sonography and catheter angiography are needed to localize these aberrant vessels.

Projection Angle

With the inherent volumetric nature of MDCT, we can easily evaluate the best pro-jection angle for visualization of any lesion while performing an endovascular interven-tion (Fig. 6). This capability is particular-ly useful when several stenoses and arter-ies need to be treated. In some institutions, MDCT is also used as a planning tool for protection devices; however, because the availability of renal protection devices is still limited, discussion is beyond the scope of this article.

Findings Beyond Renal Arteries

Renin-Secreting Tumor

Patients with renin-secreting tumor also present with resistant hypertension [3, 4]. These tumors are uncommon, with only eight cases per 30,000 hypertensive patients, and diagnosis is usually delayed because they are misdiagnosed as renal cysts or are even just overlooked (Fig. 7). These tumors are small and are easily obscured by hetero-geneous enhancement in the arterial phase, emphasizing the importance of the delayed

parenchymal phase. For young hypertensive patients with patent renal arteries and sec-ondary hyperaldosteronism, renin-secreting tumor should be suspected if a complicated cyst or renal tumor is found on cross-section-al imaging techniques such as sonography, MDCT, or MRI [3, 4].

Adrenal Lesions

Adrenal lesions—for example, pheochro-mocytoma, adrenal cortical hyperplasia (Fig. 8), and cortical adenoma—can also cause resistant hypertension [5]. Thus, a compre-hensive evaluation of a patient with resistant hypertension should include the bilateral ad-renal glands to see whether there are masses, nodules, or hypertrophy.

Renal Cell Carcinoma

Resistant hypertension can be associated with renal cell carcinoma [11]. Some patients initially suspected of having renal artery stenosis later prove to have renal cell carci-noma (Fig. 9). The size, enhancement, and vessel invasion of the tumor can be correctly assessed by a combined reading of arterial and parenchymal phase images.

Renal Stone

Renal stone formation is thought to be re-lated to the microenvironment of the kidney [12]. Hypertension and renal stone formation have many common inducing factors [12]. Many patients who present with resistant hypertension are later found to have renal stones. Removing the stone and its local irri-tation sometimes relieves the hypertension.

Page Kidney

After trauma or anticoagulant use, in some patients, a hematoma develops in the subcap-sular region of the kidney. With the com-pression effect of the hematoma to the renal parenchyma, the renin–angiotensin–aldo-sterone system could be activated and pres-ent hypertension clinically. The condition is named “Page kidney” and can be diagnosed with a typical history and visualization of the subcapsular hematoma on MDCT [23]. Comprehensive MDCT Reporting

In a comprehensive report, the follow-ing clinical questions should be answered: Is there a renal artery stenosis (Figs. 1–3)? How severe is the stenosis (Fig. 1)? Have the accessory renal arteries been identified and evaluated (Fig. 6)? What is the best projec-tion angle with which to show the stenosis

for endovascular intervention (Fig. 6)? Was the patient treated by stenting (Fig. 4)? If yes, was the intrastent lumen patent, restenosed, or occluded (Fig. 4)? Are there any other findings about the renal parenchyma (Figs. 5, 7, 9), adrenal glands (Fig. 8), or the abdomen (Fig. 2)? With this comprehensive approach, we can make the best use of the MDCT scans to provide important information to the clini-cian, the interventionist, and the patient. Conclusion

For the evaluation of patients with suspect-ed renal hypertension, we can use MDCT to offer information about the renal arteries, re-nal and perirere-nal regions, and whole scanned abdomen. Radiologists should equip them-selves with the knowledge to set the proto-col, adjust the radiation dose, and interpret the MDCT scans comprehensively.

References

1. Fraioli F, Catalano C, Bertoletti L, et al. Multide-tector-row CT angiography of renal artery steno-sis in 50 consecutive patients: prospective inter-observer comparison with DSA [in English and Italian]. Radiol Med 2006; 111:459–468 2. Rountas C, Vlychou M, Vassiou K, et al. Imaging

modalities for renal artery stenosis in suspected renovascular hypertension: prospective intra-individual comparison of color Doppler US, CT angiography, GD-enhanced MR angiography, and digital subtraction angiography. Ren Fail 2007; 29:295–302

3. Chung CT, Chen JW, Wu TR, et al. Secondary hypertension due to renin secreting tumor: a case report. Zhonghua Yi Xue Za Zhi (Taipei) 1994; 54:188–192

4. Haab F, Duclos JM, Guyenne T, et al. Renin se-creting tumors: diagnosis, conservative surgical approach and long-term results. J Urol 1995; 153: 1781–1784

5. Capricchione A, Winer N, Sowers JR. Adrenocor-tical hypertension. Curr Urol Rep 2006; 7:73–79 6. Ozkan U, Oğuzkurt L, Tercan F, Kizilkiliç O,

Koç Z, Koca N. Renal artery origins and varia-tions: angiographic evaluation of 855 consecutive patients. Diagn Interv Radiol 2006; 12:183–186 7. Raman SS, Pojchamarnwiputh S, Muangsomboon

K, Schulam PG, Gritsch HA, Lu DS. Utility of 16-MDCT angiography for comprehensive preop-erative vascular evaluation of laparoscopic renal donors. AJR 2006; 186:1630–1638

8. Tsai WL, Tsai IC, Lee T, Hsieh CW. Polyarteritis nodosa: MDCT as a “one-stop shop” modality for whole-body arterial evaluation. Cardiovasc

Inter-vent Radiol 2008; 31[suppl 2]:S26–S29

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WC. Homogeneous enhancement in pediatric thoracic CT aortography using a novel and repro-ducible method: contrast-covering time. AJR 2007; 188:1131–1137

10. Nakayama Y, Awai K, Funama Y, et al. Abdomi-nal CT with low tube voltage: preliminary obser-vations about radiation dose, contrast enhance-ment, image quality, and noise. Radiology 2005; 237:945–951

11. Wong PS, Lip GY, Gearty JC, et al. Renal cell car-cinoma and malignant phase hypertension. Blood

Press 2001; 10:16–21

12. Borghi L, Meschi T, Guerra A, et al. Essential ar-terial hypertension and stone disease. Kidney Int 1999; 55:2397–2406

13. Garovic VD, Textor SC. Renovascular hyperten-sion and ischemic nephropathy. Circulation 2005; 112:1362–1374

14. McCullough PA. Contrast-induced acute kidney injury. J Am Coll Cardiol 2008; 51:1419–1428 15. Goske MJ, Applegate KE, Boylan J, et al. The

“Image Gently” campaign: increasing CT radia-tion dose awareness through a naradia-tional educaradia-tion and awareness program. Pediatr Radiol 2008; 38:265–269

16. McCollough C, Cody D, Edyvean S, et al.; Diag-nostic Imaging Council CT Committee. The mea-surement, reporting, and management of radiation dose in CT. College Park, MD: American Asso-ciation of Physicists in Medicine, January 2008: AAPM report no. 96

17. Saba L, Caddeo G, Sanfilippo R, Montisci R, Mallarini G. Multidetector-row CT angiography diagnostic sensitivity in evaluation of renal artery stenosis: comparison between multiple recon-struction techniques. J Comput Assist Tomogr 2007; 31:712–716x

18. Puchner S, Stadler A, Minar E, Lammer J, Bucek RA. Multidetector CT angiography in the follow-up of patients treated with renal artery stents: value of different reformation techniques com-pared with axial source images. J Endovasc Ther

2007; 14:387–394

19. Sabharwal R, Vladica P, Coleman P. Multidetec-tor spiral CT renal angiography in the diagnosis of renal artery fibromuscular dysplasia. Eur J Radiol 2007; 61:520–527

20. Kawashima A, Sandler CM, Ernst RD, Tamm EP, Goldman SM, Fishman EK. CT evaluation of renovascular disease. RadioGraphics 2000; 20: 1321–1340

21. Cheng BC, Ko SF, Chuang FR, Lee CH, Chen JB, Hsu KT. Successful management of acute renal artery thromboembolism by intra-arterial throm-bolytic therapy with recombinant tissue plasmino-gen activator. Ren Fail 2003; 25:665–670 22. Salam TA, Lumsden AB, Martin LG. Local

infu-sion of fibrinolytic agents for acute renal artery thromboembolism: report of ten cases. Ann Vasc

Surg 1993; 7:21–26

23. Haydar A, Bakri RS, Prime M, Goldsmith DJ. Page kidney: a review of the literature. J Nephrol 2003; 16:329–333

A

Fig. 1—46-year-old man with resistant hypertension who underwent renal artery stenosis survey. Body weight

of patient was 100 kg. This case shows scanning protocol, image postprocessing, and interpretation algorithm.

A, Scout film of scan. After scout image is obtained, scan ranges of arterial phase (A) and parenchymal

phase (P) are defined. Abdominal lateral width (LW) at kidney level is then measured to determine radiation parameters according to Table 1.

B, Axial thin-section (0.67-mm) image of arterial phase MDCT. Image is displayed in routine CT angiography

window with center of 40 HU and width of 400 HU. Obvious image noise can be identified—for example, within aorta (arrow) and pancreatic head parenchyma (arrowhead). Noise level measured in aorta is 41 HU, which makes routine image interpretation difficult.

C, Axial thick-section (3-mm) image of arterial phase MDCT. When thickness is increased, noise is greatly

reduced compared with B. Also, viewing image in wider window width (800 HU) further reduces perceived image noise. Radiologist could use this image setting to scroll up and down to evaluate whole abdomen. Note significantly decreased noise in aorta (arrow) and pancreatic head parenchyma (arrowhead) compared with B.

(Fig. 1 continues on next page)

C B

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E D

Fig. 1 (continued)—46-year-old man with resistant hypertension who underwent renal artery stenosis survey. Body weight of patient was 100 kg. This case shows

scanning protocol, image postprocessing, and interpretation algorithm.

D, Oblique coronal image obtained for evaluation of right renal artery (arrow) with maximum-intensity-projection technique is then evaluated for any stenosis. Mixed

plaque causing stenosis is noted over proximal right renal artery (arrowhead). Ao = aorta, RK = right kidney.

E, Zoomed oblique coronal image obtained for evaluation of proximal right renal artery stenosis lesion is used to quantifystenosis. Measuring most stenotic segment (arrowhead) and comparing it with proximal referenced vessel (arrow), we can quantify stenosis. In this case, stenotic segment is 3.2 mm in diameter and reference vessel is 5.6 mm in diameter, which creates stenosis of 43% [(5.6 mm – 3.2 mm) / 5.6 mm]. Endovascular revascularization is not indicated.

F, Oblique coronal slab volume-rendered image obtained for evaluation of right renal artery and right kidney. Volume-rendering technique provides good panoramic view,

but it is not accurate in quantifying stenosis (arrowhead) because degree of stenosis is greatly affected by many parameters of volume-rendering technique such as opacity, threshold, and light source direction.

G, Coronal thin-section (0.8-mm) image of low-dose 4-minute parenchymal phase scan. Because of low-radiation technique, image noise is high (81.3 HU), which makes

interpretation very difficult. Note noisy image in homogeneously enhanced renal parenchyma (arrowhead).

H, Coronal thick-section (8-mm) of low-dose 4-minute parenchymal phase scan. By increasing thickness, noise level dropped to 23.2 HU, which is good for clinical

interpretation. Renal parenchyma (arrowhead) and collecting system (arrow) can be thoroughly evaluated. Note significantly decreased noise in renal parenchyma compared with G. Parenchymal phase imaging is good for detection of small tumors such as renin-secreting tumors.

H G

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A

C

Fig. 2—73-year-old man diagnosed as having atherosclerotic bilateral renal artery stenoses who underwent

endovascular treatment.

A, Coronal thin-section image shows right-side 90% (arrowhead) and left-side 70% (arrow) renal artery stenoses.

In atherosclerotic renal artery stenosis, plaque can always be identified. In this case, right-side renal artery stenosis is caused by noncalcified plaque, and left-side renal artery is stenosed by mixed plaque. Ao = aorta.

B, Oblique sagittal slab volume-rendered image shows another critical stenosis over celiac ostium (arrow).

Because atherosclerosis is systemic disease, multivessel involvement is common. All major arteries in scanned region must be evaluated to provide comprehensive report.

C, Oblique coronal volume-rendering image shows poor bilateral lower limb arterial conditions. Chronic total

occlusion is noted over right common femoral artery (dotted line) and left superficial femoral artery (dashed

line). Left external iliac artery also shows critical lesion (arrowhead). For endovascular intervention, femoral

artery approach is thus not suggested. In report, interpreting radiologist suggested upper limb approach for renal artery intervention.

D, Anteroposterior view of catheter angiography shows right renal artery stenosis is so critical that stenotic

lumen (arrowhead) is barely visible. Guidewire passage confirmed lesion was critically stenotic rather than chronically occluded. Also, note that catheter reaches renal artery via radial artery approach, as radiologist suggested in report.

E, Anteroposterior view of catheter angiography for left renal artery shows left renal artery stenosis of 70%

(arrow). Both lesions in renal arteries were then treated by angioplasty and stenting. B

D

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B

A

A

Fig. 3—24-year-old woman with resistant hypertension due to fibromuscular

dysplasia.

A, Oblique axial slab volume-rendered image. Viewing angle is from diaphragm to

be able to see abdominal vessels, with patient’s left side on left side of image. Both right-side (arrowhead) and left-side (arrow) renal artery stenoses can be clearly identified. Ao = aorta, CT = celiac trunk.

B, Axial maximum-intensity-projection image of right renal artery shows near total

occlusion (arrowhead) over right proximal renal artery. Note stenosis is not caused by atherosclerosis; thus, no plaque can be seen.

C, Oblique coronal maximum-intensity-projection image of left renal artery shows

critical lesion (arrow) over proximal left renal artery. Also, no plaque can be seen in this lesion.

Fig. 4—24-year-old woman (same patient as in Figure 3) who underwent bilateral

renal artery stenting for treatment of fibromuscular dysplasia.

A, Coronal slab volume-rendered image shows stent is placed over left (arrow)

and right (arrowhead) proximal renal arteries. However, because of native vessel curvature, left renal artery stent shows angulation (arrow).

(Fig. 4 continues on next page)

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Fig. 4 (continued)—24-year-old woman (same patient

as in Figure 3) who underwent bilateral renal artery stenting for treatment of fibromuscular dysplasia.

B, Thin-section oblique coronal image obtained

for evaluation of left renal artery stent shows kink (arrow) over middle portion of stent with some intimal hyperplasia (thin black lining inside stent), but lumen is still patent.

C, Thin-section axial image obtained for evaluation of

right renal artery stent shows patent intrastent lumen (arrowhead). Note that percutaneous transluminal renal artery angioplasty with stenting is standard treatment of fibromuscular dysplasia–associated renal hypertension. In most cases, stenting will result in good symptom relief.

B C

A

Fig. 5—48-year-old man who experienced right flank pain and resistant

hypertension for 4 days and who was diagnosed as having right renal artery thromboembolism with renal infarction.

A, Coronal slab volume-rendered image shows long segment of filling defect over

right renal artery (arrowhead) with poorly enhanced right kidney (asterisk) as compared with left kidney (arrow).

B, Coronal thin-section image obtained for evaluation of distal right renal artery

and right kidney shows long segment of filling defect over right distal renal artery and poor enhancement over renal parenchyma particularly over renal cortex, which is more susceptible to ischemic injury. Right renal artery thromboembolism (arrowheads) with renal infarction (asterisk) was diagnosed.

C, Coronal image obtained for bilateral kidney comparison shows poorly enhanced

right kidney with cortical necrosis (asterisk). Normal left kidney shows enhanced renal cortex (arrow), medulla, and collecting system.

C B

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A

C

Fig. 6—83-year-old woman who was diagnosed with

renal artery stenosis. This case shows importance of identifying accessory renal arteries and providing projection angle information.

A, Oblique coronal maximum-intensity-projection

image obtained for evaluation of right renal arteries shows two renal arteries: Upper one is large (arrow) and lower one is smaller (arrowhead). If right lower renal artery, which has significant ostial stenosis, had not been identified, diagnosis and treatment might have been delayed. Ao = aorta, RK = right kidney.

B, Axial thin-section image obtained for evaluation

of ostial stenosis of right inferior renal artery clearly shows stenosis (arrowhead). Best projection angle by which to approach lesion for catheter angiography is left anterior oblique 35° angle, which is shown by dashed line. Black solid line shows true anteroposterior projection.

C, True anteroposterior projection of catheter

angiography for right renal artery injection cannot clearly show ostial lesion (arrowhead).

D, Left anterior oblique 35° projection of catheter

angiography obtained for evaluation of right renal artery clearly shows ostial lesion (arrowhead). Interventionist might have overlooked ostial lesion if he or she had not been provided with projection angle information before procedure. Because of volumetric acquisition nature of MDCT, it is easy to find best projection angle for any renal stenotic lesion.

B

D

A

Fig. 7—10-year-old girl with elevated renin and resistant hypertension who was diagnosed as having

renin-secreting tumor. C = cortex, M = medulla.

A, Axial image obtained in arterial phase shows poorly enhanced small nodule over right kidney (arrowhead).

This tumor was initially misdiagnosed as prominent medulla or small renal cyst on arterial phase image by experienced radiologist. Note that in arterial phase, renal parenchyma enhancement is very heterogeneous, making evaluation of parenchyma difficult.

B, Axial image obtained in 4-minute parenchymal phase shows mild peripheral enhancement of tumor

(arrowhead) that can be easily identified because of homogeneous enhancement of renal parenchyma. With percutaneous technique, lesion was confirmed to be renin-secreting tumor and was treated by cryotherapy. Resistant hypertension was then cured. Without parenchymal phase image, conclusion of MDCT study might have been “no renal artery stenosis,” and diagnosis might have been delayed for years. This case illustrates importance of parenchymal phase scan for comprehensive evaluation.

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Fig. 8—69-year-old man who was diagnosed with

resistant hypertension due to unilateral adrenal cortical hyperplasia. Oblique coronal image of left renal artery (arrow) and left adrenal gland (arrowhead) shows patent left renal artery and hypertrophied left adrenal gland, which is 10 mm in thickness. Left adrenal gland was then resected and resistant hypertension was cured. Ao = aorta.

Fig. 9—78-year-old man who was initially suspected

to have renal hypertension but was later diagnosed as having renal cell carcinoma. Oblique coronal image of right kidney and renal vein shows 48-mm mass lesion (arrow) over upper pole of right kidney with renal vein thrombosis (arrowhead), which is a typical finding for renal cell carcinoma. Right nephrectomy confirmed diagnosis. IVC = inferior vena cava.

數據

Fig. 1 (continued)—46-year-old man with resistant hypertension who underwent renal artery stenosis survey
Fig. 4 (continued)—24-year-old woman (same patient  as in Figure 3) who underwent bilateral renal artery  stenting for treatment of fibromuscular dysplasia.

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ESDA is used by schools to collect and manage self-evaluation data, including the administration of on-line Stakeholder Survey (SHS), assessing students’ affective and