Pediatric Imaging Review

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1 Pediatric Imaging Review Castelli et al. Renin-Mediated Hypertension in Children Pediatric Imaging Review Patricia K. Castelli 1 Jonathan R. Dillman 1 Ethan. Smith 1 Ranjith Vellody 2 Kyung Cho 2 James C. Stanley 3 Castelli PK, Dillman JR, Smith E, Vellody R, Cho K, Stanley JC Keywords: children, hypertension, imaging, renal artery stenosis, renin, renovascular hypertension DOI: /JR Received June 16, 2012; accepted after revision July 9, Department of Radiology, Section of Pediatric Radiology, University of Michigan Health System, C. S. Mott Children s Hospital, 1540 E Hospital Dr, nn rbor, MI ddress correspondence to J. R. Dillman (jonadill@med.umich.edu). 2 Department of Radiology, Division of Vascular and Interventional Radiology, University of Michigan Health System, nn rbor, MI. 3 Department of Surgery, Section of Vascular Surgery, University of Michigan Health System, nn rbor, MI. WE This is a Web exclusive article. JR 2013; 200:W661 W X/13/2006 W661 merican Roentgen Ray Society Imaging of Renin-Mediated Hypertension in Children OJECTIVE. The purpose of this article is to review the imaging findings of common and uncommon causes of renin-mediated hypertension in children using a multimodality radiologic approach. CONCLUSION. Pediatric hypertension, although uncommon, is often due to aortic or renal artery narrowing. Imaging plays an important role in the diagnosis and characterization of pediatric renin-mediated causes of hypertension. P ediatric hypertension is uncommon, occurring in 2 5% of children [1, 2]. Secondary causes are much more frequent in the pediatric population, with renin-mediated blood pressure elevation due to aortic or renovascular narrowing accounting for about 5 10% of cases of childhood hypertension [3, 4]. Hypoperfusion and dampening of normally pulsatile renal blood flow result in increased renin release from the juxtaglomerular apparatus of the kidney and activation of the renin-angiotensin cascade pathway (Fig. 1). This type of hypertension is often refractory to conventional medical therapy and, if untreated, can lead to serious complications, including hypertensive encephalopathy and stroke, left ventricular hypertrophy with diastolic dysfunction and congestive heart failure, and diminished renal function [1, 5, 6]. The authors and their colleagues at the University of Michigan have treated 176 children with aortic or renal artery disease contributing to uncontrolled hypertension, including performance of 267 surgeries in 112 patients with renal artery disease alone, 47 with both aortic and renal artery disease, and 14 with narrowing limited to the abdominal aorta. Three other patients had extravascular lesions causing arterial narrowing. ll patients underwent preoperative imaging, with the majority having undergone two or more preoperative radiologic imaging studies, resulting in a large diverse collection of imaging studies depicting the causes of this important form of hypertension. The purpose of this review is to illustrate the imaging appearances of a variety of com- mon and uncommon causes of renin-mediated hypertension in children. High-quality preoperative imaging is mandatory for planning the appropriate treatment, including both catheterbased interventions and conventional arterial reconstructive surgical procedures [6]. Imaging of Renin-Mediated Hypertension The causes of pediatric renin-mediated hypertension may be detected and characterized using an assortment of imaging modalities, including renal Doppler sonography, CT angiography (CT), MR angiography (MR), and catheter-based angiography [7]. Imaging of aortic and renovascular causes of hypertension in children is uniquely challenging because of the small caliber of their blood vessels; their hyperdynamic cardiovascular system, which affects timing of image acquisition with respect to contrast material injection; and the desire to minimize ionizing radiation exposure [7, 8]. Renal Doppler Sonography dvantages of renal Doppler sonography include its lack of ionizing radiation exposure, relatively low cost, and widespread availability. This imaging technique is very operator dependent, however, and requires operator (either physician or technologist) experience and comfort. In addition, small vascular structures, including the main renal arteries in young children, as well as accessory renal arteries in patients of all ages, may be difficult to visualize directly [7, 8]. s a result, secondary signs are often relied on to confirm the presence of more proximal arte- JR:200, June 2013 W661

2 Castelli et al. TLE 1: Institutional CT ngiography Protocol for Evaluating the bdominal orta and Renal rteries in the Setting of Suspected Renin-Mediated Hypertension Parameter rial narrowing, including tardus parvus spectral Doppler waveforms and abnormally low intrarenal resistive index measurements [8]. Value Scanner mode Helical Gantry rotation time (s) 0.5 Detector configuration (mm) Pitch 1.375:1 Speed (mm/rotation) 27.5 Kilovoltage (kvp) 100 Tube current (m) utomatic modulation Noise index 28 Contrast agent volume (ml/kg) a 2 Injection rate with power injector (ml/s) 2 4 Contrast timing SmartPrep (GE Healthcare) b Image reconstruction Section thickness (mm) 2.5 Section overlap (mm) 1.25 Note We used a Discovery CT750 HD scanner (GE Healthcare) using adaptive statistical iterative reconstruction. Images were reviewed on a workstation capable of generating 2D multiplanar reformatted and 3D reconstructed images. a Maximum volume was 125 ml. b region of interest was placed over the aorta at the level of the celiac artery. Cross-Sectional ngiography (CT and MR) dvantages of CT include its ability to very rapidly image thoracic and abdominal arterial structures, resulting in fewer motionrelated artifacts and less need for sedation or general anesthesia compared with MR. CT provides excellent spatial and contrast resolution, allowing high-quality multiplanar 2D reformats and 3D reconstructions. Disadvantages of CT include ionizing radiation exposure and the need for IV iodinated contrast material. dvantages of MR include excellent contrast resolution allowing 2D reformats and 3D reconstructions, the ability to obtain images either without or with IV contrast material, and the lack of ionizing radiation exposure. Disadvantages of MR compared with CT include lower spatial resolution that limits successful evaluation of intrarenal renal artery branches and small accessory renal arteries, the potential to exaggerate areas of arterial narrowing, and the presence of artifacts due to implanted metal or patient motion [8]. In addition, MR generally has a higher cost and less availability compared with CT, and younger pediatric patients generally require some form of sedation or general anesthesia during the study period. Our institutional CT and MR protocols for evaluating the abdominal aorta and renal arteries in the setting of suspected renin-mediated hypertension are presented in Tables 1 and 2. Catheter-ased ngiography Catheter-based angiography is generally considered the reference standard for diagnosing aortic and renovascular causes of hypertension, primarily because of its excellent spatial and contrast resolution [3, 5, 7]. Catheter-based imaging techniques have the additional advantage of allowing concomitant treatment of some lesions as part of the same procedure [3]. The primary disadvantage of catheter-based angiography is its invasive nature, which puts the child at risk for a variety of vascular complications, including arterial dissection, thrombosis, and embolic phenomenon. Catheter-based angiography also requires ionizing radiation exposure, intravascular iodinated contrast material, and sedation or general anesthesia. The most common catheter-based angiography approach for evaluating the aorta and its branches is intraarterial digital subtraction angiography (DS) [9]. This is usually performed from a common femoral artery approach. Using a small (3- or 4-French) flush catheter, aortic pressures can be measured from the ascending thoracic aorta to the distal abdominal aorta. If no significant aortic pressure gradient is found, the catheter is TLE 2: Institutional MR ngiography (MR) Protocol for Evaluating the bdominal orta and Renal rteries in the Setting of Suspected Renin-Mediated Hypertension Sequence T2-weighted turbo spin-echo Plane Coronal and sagittal Fat Saturation Flip ngle ( ) TR/TE Slice Thickness/ Gap (mm) No. of Signal verages Respiration No 90 Shortest a /100 5/0 2 Respiratory triggered T2-weighted turbo spin-echo xial Yes 90 Shortest a /100 5/1 2 Respiratory triggered Contrast-enhanced dynamic Coronal No 40 Shortest a /Shortest a 2/0 2 reath-hold 3D MR b 3D phase-contrast MR Coronal No 15 Shortest a /5 3/0 1 Free breathing Contrast-enhanced T1-weighted 3D spoiled gradient-recalled echo xial Yes 10 Shortest a /Shortest a 3/0 1 reath-hold Note We used a 1.5-T Ingenia scanner (Philips Healthcare). Images were reviewed on a workstation capable generating 2D multiplanar reformatted and 3D reconstructed images. a Shortest TR or TE allowed by the scanner. b Three dynamic series were obtained, including the arterial phase. W662 JR:200, June 2013

3 Renin-Mediated Hypertension in Children then generally placed in the abdominal aorta for anteroposterior and lateral aortography. fter aortography, the flush catheter can be exchanged for a small (3- or 4-French) cobra or a reversed curve catheter for selective catheterization of the renal arteries. Renal angiography is then performed in the anteroposterior and bilateral oblique projections to evaluate segmental and more distal intrarenal renal arteries [9]. less commonly used approach for evaluating the aorta and its branches is IV DS, with contrast material injection into either a central vein or the right atrium [9]. This technique does not require arterial puncture and is useful in children younger than 3 years. Disadvantages of IV DS compared with intraarterial DS include a requirement for larger volumes of injected contrast material and the fact that it does not allow selective renal arteriography. IV DS generally can be performed using a basilic vein approach on an outpatient basis. If the basilic vein is not available, either an internal jugular or common femoral vein approach may be used for the introduction of a small flush catheter into the central venous circulation or right atrium. Imaging should be initiated approximately 4 seconds after the start of contrast material injection to allow time for passage through the heart and lungs into the aorta. Thoracic and bdominal ortic Causes of Pediatric Hypertension ortic Interruption ortic interruption, or the developmental absence of a portion of the thoracic or abdominal aorta, is usually secondary to either primary agenesis or congenital in utero occlusion. lthough this process most commonly occurs within the aortic arch and is frequently associated with chromosome 22q11 deletion [10, 11], other aortic segments may be involved. When the aortic arch is interrupted, a patent ductus arteriosus is usually present, supplying blood flow to the descending thoracic aorta, abdomen, and lower extremities [11, 12]. If the interruption is distal to the level of the aortic arch, a variety of arterial collateral pathways can be seen, depending on the exact location and length of interruption (Figs. 2 and 3). Postinterruption aneurysm formation may occur (Fig. 3). ortic Coarctation ortic coarctation, or focal aortic stenosis of variable severity, most commonly involves the distal aortic arch or proximal descending thoracic aorta in the region of the aortic isthmus [10] (Fig. 4). ortic coarctation less commonly affects the lower thoracic or abdominal aorta (Fig. 5). The latter involves the suprarenal aorta more commonly than the infrarenal aorta [13]. variety of collateral pathways may be observed, depending on the exact location and degree of narrowing. Thoracic aortic coarctation can occur sporadically or may be associated with genetic abnormalities, such as Turner syndrome (45 XO syndrome) [14]. Certain cardiac anomalies, such as bicuspid aortic valve, are also associated with thoracic aortic coarctation. When aortic coarctation is suprarenal, Doppler sonography often reveals more distal aortic and bilateral renal artery tardus parvus waveforms (Fig. 4). CT and catheter-based angiography both provide excellent images of focal aortic narrowing and associated collateral vessels. MR can provide a noninvasive estimate of the pressure gradient across the site of coarctation using phase-contrast techniques. However, catheter-based angiography allows direct measurements of pressure gradients across the site of narrowing and provides the opportunity to undertake therapeutic angioplasty or stent placement. bdominal aortic coarctation commonly coexists with renal and mesenteric artery stenoses in children [6, 13] (Fig. 5). CT and MR 2D reformations and 3D reconstructions of arterial structures help detect areas of narrowing and collateral pathways that may be difficult to appreciate in the axial plane alone [15]. ortic Hypoplasia ortic hypoplasia, or long-segment developmental narrowing of the aorta, usually affects the lower thoracic or upper abdominal aorta. This condition may be present in children with neurofibromatosis type 1, Williams syndrome, and isolated developmental arterial dysplasia (sometimes classified as fibromuscular dysplasia) [13]. Similar-appearing aortic narrowing has also been described in children with neuroblastomas who did and did not undergo abdominal radiation therapy [16, 17]. ortic hypoplasia can be variable in length and degree of narrowing, without evidence of mural thickening or adjacent inflammatory changes to suggest underlying vasculitis (Fig. 6). variety of collateral pathways may be observed depending on the exact location and degree of narrowing. s in the case of focal abdominal aortic coarctation, there are often coexistent renal and mesenteric arterial stenoses [13] (Figs. 6 and 7). Treatment is typically surgical, requiring either patch aortoplasty or an aortic bypass [3, 13] (Fig. 7). bdominal ortic neurysm bdominal aortic aneurysms are very rare in children. There are a variety of causes, including congenital abnormalities (Fig. 3), developmental arterial dysplasia, connective tissue disorders (e.g., Marfan syndrome and Ehlers-Danlos syndrome), infection (mycotic), trauma, vasculitis (e.g., Takayasu arteritis and Kawasaki disease), tuberous sclerosis (Fig. 8), and poststenotic abnormalities [18, 19] (Fig. 9). ffected patients may present with hypertension if the renal arteries arise from the aneurysm sac and become stenotic, occluded, or extrinsically compressed by the aneurysm (Figs. 3, 8, and 9). s in adults, the morphologic features of these aneurysms can be either saccular or fusiform. Treatment is typically surgical resection of the aneurysm with an aortic reconstruction to prevent aneurysm-related complications, including rupture, thrombosis, and embolism [19]. Renal rtery Pathologic bnormalities Developmental rterial Dysplasia Developmental arterial dysplasia is the most common cause of renal artery stenosis in children [4, 6, 7]. lthough it was previously thought to be a variant of adult fibromuscular dysplasia, developmental arterial dysplasia is now considered to be a distinct entity. Histopathologically, there is typically a combination of abnormalities present, including intimal fibroplasia, medial thinning, and excessive external elastic lamina [6, 20]. Developmental arterial dysplasia may affect the renal arteries, as well as extrarenal arterial structures, such as the mesenteric and carotid arteries [20]. In our experience, the proximal portions of the renal arteries are most often involved with stenoses (first- or second-order arteries), with bilateral narrowing in approximately 30 40% of cases [6] (Figs. 10 and 11). Intrarenal (third order) and accessory renal artery focal stenoses may also occur, usually requiring catheter-based angiography for diagnosis and identification of collateral vessels [5] (Fig. 12). Renal artery aneurysmal dilatation sometimes occurs just distal to areas of focal stenosis and may be associated with embolic phenomena, including renal infarction (Fig. 13). lthough catheter-based interventions may be attempted to improve blood flow to the kidney, in our experience, surgery has usually been the primary treatment option. Depending on the site, length, and degree of renal artery narrowing, a variety of surgical procedures may be per- JR:200, June 2013 W663

4 Castelli et al. formed, including renal artery reimplantation (into the abdominal aorta, adjacent renal artery branches, and the superior mesenteric artery), bypass (aortorenal or iliorenal), focal renal arterioplasty, stenosis resection with a primary reanastomosis, and, in the face of irreparable arterial disease, a primary nephrectomy [6]. Neurofibromatosis type 1, an autosomal dominant phakomatosis (or neurocutaneous disorder), is recognized as the underlying primary disease in a subgroup of children with renal artery developmental dysplasia. This condition is responsible for a substantial percentage of pediatric renovascular hypertension cases, ranging from 7% to 58% in the literature [3]. Renal artery narrowing in this setting is most commonly due to arterial mesodermal dysplasia and less often to mass-effect from neurofibromas within the adventitia of the artery or adjacent to the artery. Common imaging findings include renal and mesenteric arterial stenoses with or without associated aneurysm formation [4, 21] (Fig. 14). ll levels of the renal artery may be involved, requiring catheter-based angiography for complete characterization [21]. bdominal aortic narrowing may also be present [4]. Inflammatory rteritis variety of inflammatory arteritides may cause renal artery narrowing, including Takayasu arteritis (Fig. 15), Kawasaki disease, and polyarteritis nodosa [3, 5]. Renal artery stenosis caused by vasculitis is much more common in sian and frican countries than in Europe and North merica [3, 4, 7]. lthough it is rare, vasculitis affecting the renal arteries is also known to occur after abdominal radiation therapy, sometimes many years after treatment [3, 22] (Fig. 16). Imaging findings suggestive of renal artery vasculitis include concentric arterial wall thickening, focal stenoses, occlusions, and aneurysms [23]. ffected kidneys may appear atrophic and hypoperfused on contrast-enhanced imaging (Fig. 16). Focal parenchymal scarring due to infarction may be observed in the setting of segmental or intrarenal arterial fibrosis or embolic occlusions. When renal artery vasculitis is suspected, prompt evaluation of the entire arterial vascular tree for other areas of involvement should be performed. Extrinsic Compression Extrinsic compression of the renal arteries with resultant narrowing is most often due to a retroperitoneal mass [3] (Fig. 17), hematoma or other focal fluid collection, aneurysm, or pseudoaneurysm (Fig. 18). These patients may present with signs and symptoms related to their underlying disease process, although renin-mediated hypertension may, on occasion, be the initial presenting ailment. Treatment of the underlying disease process often results in resolution of hypertension in these patients. In the setting of neuroblastoma, however, aortic and renal artery narrowing may persist after treatment with continued hypertension [16]. Conclusion lthough hypertension is relatively uncommon in the pediatric age group compared with the adult population, it is more likely to be the result of a secondary cause, including aortic or renal artery narrowing. ecause the clinical diagnosis of renin-mediated hypertension is often challenging in children, imaging plays important roles in confirming the exact diagnosis and in the planning of optimal treatment. variety of imaging modalities, including renal Doppler sonography, CT, MR, and catheter-based angiography, can be used to successfully identify and characterize vascular causes of hypertension in children and adolescents. References 1. Mitsnefes MM. Hypertension in children and adolescents. Pediatr Clin North m 2006; 53: Hansen ML, Gunn PW, Kaelber DC. Underdiagnosis of hypertension in children and adolescents. JM 2007; 298: Tullus K, rennan E, Hamilton G, et al. Renovascular hypertension in children. Lancet 2008; 371: Srinivasan, Krishnamurthy G, Fontalvo-Herazo L, et al. Spectrum of renal findings in pediatric fibromuscular dysplasia and neurofibromatosis type 1. Pediatr Radiol 2011; 41: Vo NJ, Hammelman D, Racadio JM, Strife FC, Johnson ND, Racadio JM. natomic distribution of renal artery stenosis in children: implications for imaging. Pediatr Radiol 2006; 36: Stanley JC, Criado E, Upchurch GR Jr, rophy PD, Cho KJ, Rectenwald JE. Pediatric renovascular hypertension: 132 primary and 30 secondary operations in 97 children. J Vasc Surg 2006; 44: Tullus K, Roebuck DJ, McLaren C, Marks SD. Imaging in the evaluation of renovascular disease. Pediatr Nephrol 2010; 25: Soulez G, Olivia VL, Turpin S, Lambert R, Nicolet V, Therasse E. Imaging of renovascular hypertension: respective values of renal scintigraphy, renal Doppler US, and MR angiography. Radio- Graphics 2000; 20: Tonkin IL, Stapleton F, Roy S 3rd. Digital subtraction angiography in the evaluation of renal vascular hypertension in children. Pediatrics 1988; 81: Goo HW, Park I, Ko JK, et al. CT of congenital heart disease: normal anatomy and typical pathologic condition. RadioGraphics 2003; 23(suppl 1):S147 S Dillman JR, Yarram SG, D mico R, Hernandez RJ. Interrupted aortic arch: spectrum of MRI findings. JR 2008; 190: Reardon MJ, Hallman GL, Colley D. Interrupted aortic arch: brief review and summary of an eighteen year experience. Tex Heart Inst J 1984; 11: Stanley JC, Criado E, Eliason JL, Upchurch GR, erguer R, Rectenwald JE. bdominal aortic coarctation: surgical treatment of 53 patients with a throacoabdominal bypass, patch aortoplasty, or interposition aortoaortic graft. J Vasc Surg 2008; 48: Mazzanti L, Caccian E. Congenital heart disease in patients with Turner s syndrome: Italian study group for Turner s syndrome (ISGTS). J Pediatr 1998; 133: Dillman JR, Hernandez RJ. Role of CT in the evaluation of congenital cardiovascular disease in children. JR 2009; 192: Levin TL, Roebuck D, erdon WE. Long-segment narrowing of the abdominal aorta and its branches in a survivor of infantile neuroblastoma treated without radiation therapy. Pediatr Radiol 2011; 41: Sutton EJ, Tong RT, Gillis M, et al. Decreased aortic growth and middle aortic syndrome in patients with neuroblastoma after radiation therapy. Pediatr Radiol 2009; 39: Sarkar R, Coran, Cilley RE, Lindenauer SM, Stanley JC. rterial aneurysms in children: clinicopathologic classification. J Vasc Surg 1991; 13: English WP, Edwards MS, Pearce JD, Mondi MM, Hundley JC, Hansen KJ. Multiple aneurysms in children. J Vasc Surg 2004; 39: Devaney K, Kapur SP, Patterson K, Chandra RS. Pediatric renal artery dysplasia: a morphologic study. Pediatr Pathol 1991; 11: Han M, Criado E. Renal artery stenosis and aneurysms associated with neurofibromatosis. J Vasc Surg 2005; 41: Himmel PD, Hasset JM. Radiation-induced chronic arterial injury. Semin Surg Oncol 1986; 2: Matsunaga N, Hayashi K, Sakamoto I, Ogawa Y, Matsumoto T. Takayasu arteritis: protean radiologic manifestations and diagnosis. RadioGraphics 1997; 17: W664 JR:200, June 2013

5 Renin-Mediated Hypertension in Children Fig. 1 Mechanism of renin-mediated hypertension due to aortic and renal artery narrowing. Fig. 2 5-year-old girl with hypertension and left ventricular hypertrophy. and, Lateral () and anteroposterior () 3D maximum-intensity-projection MR angiography images show long-segment complete interruption of descending thoracic aorta (arrow, ). There is abdominal aortic reconstitution from chest and abdominal wall, paraspinal, and intercostal collateral arteries (arrowheads). JR:200, June 2013 W665

6 Castelli et al. C Fig. 3 3-month-old boy with hypertension and multiple congenital anomalies. and, Three-dimensional volume-rendered (anteroposterior projection) () and maximumintensity-projection (lateral projection) () MR angiography images show complete interruption of descending thoracic aorta (arrows). There is aortic reconstitution from extensive paraspinal collateral arteries. lso, there is large postinterruption fusiform aortic aneurysm (asterisks) and ostial stenosis of right renal artery. Fig year-old boy with incidentally detected hypertension. and, Spectral Doppler ultrasound images of main renal arteries show bilateral tardus parvus waveforms () and abnormally low resistive indexes (). C, Lateral 3D maximum-intensity-projection MR angiography image shows severe focal narrowing (arrow) of thoracic aorta, just distal to left subclavian artery, consistent with isthmic aortic coarctation. Numerous collateral arteries are seen, including enlarged internal mammary, paraspinal, and intercostal arteries. W666 JR:200, June 2013

7 Renin-Mediated Hypertension in Children Fig. 5 5-year-old girl with incidentally detected hypertension. nteroposterior 3D maximum-intensity-projection MR angiography image shows severe focal narrowing (arrow) of upper abdominal aorta near level of diaphragm. There is also severe bilateral proximal and mid renal artery narrowing (arrowheads). Fig year-old boy with hypertension and abdominal aortic hypoplasia. nteroposterior 3D maximum-intensity-projection MR angiography image shows that right renal artery is proximally stenotic (solid arrowhead), whereas left kidney is surgically absent. There is severe narrowing of abdominal aorta (solid arrow) at and just below level of right renal artery. From supraceliac aorta to inframesenteric aorta, 10-mm polytetrafluoroethylene bypass graft is patent (open arrowheads). Patent 6-mm polytetrafluoroethylene bypass graft extending from aortoaortic graft to right common femoral artery (open arrow) was placed for occluded right common and external iliac arteries. Multiple wedge-shaped areas of nonenhancing renal parenchymal scarring are present. Fig. 6 6-year-old girl with hypertension. and, nteroposterior 3D volume-rendered () and axial () CT angiography images show long-segment severe narrowing of mid abdominal aorta (arrows). lso, there are two right renal arteries (arrowheads) that are both severely narrowed proximally. Left kidney is congenitally absent, and collateral vessels are present within mesentery and abdominal wall. JR:200, June 2013 W667

8 Castelli et al. Fig. 8 7-year-old boy with hypertension and tuberous sclerosis. and, nteroposterior 3D maximum-intensityprojection () and volume-rendered () MR angiography images show saccular suprarenal abdominal aortic aneurysm (asterisks) involving origins of celiac axis, superior mesenteric artery, and right renal artery. There is high-grade narrowing of right renal artery proximally (arrows). Fig. 9 2-month-old boy with hypertension., nteroposterior 3D maximum-intensity-projection arterial phase MR angiography image shows poststenotic irregular fusiform abdominal aortic aneurysm (arrows) extending from just below diaphragm to just above inferior mesenteric artery. Renal arteries and celiac axis are occluded at their origins. Origin of superior mesenteric artery is narrowed (solid arrowhead) with poststenotic dilatation, whereas inferior mesenteric artery is dilated (open arrowhead). Kidneys are poorly seen because of hypoperfusion., Venous phase image shows nonenhancement of left kidney upper pole due to infarction (arrow). Enhancement of right kidney and left kidney lower pole is likely due to collateral blood flow. Fig year-old girl with hypertension. and, ilateral oblique subvolume 3D maximumintensity-projection CT angiography images show bilateral high-grade proximal renal artery stenoses (arrows). Tortuous arterial collateral vessels are seen along course of right ureter (arrowheads, ). W668 JR:200, June 2013

9 Renin-Mediated Hypertension in Children Fig year-old girl with hypertension. Selective catheter-based angiographic image of right renal artery (second right renal artery provided blood flow to right kidney lower pole; not shown) reveals high-grade focal stenosis (arrow) involving second-order branch with poststenotic dilatation. C Fig year-old girl with hypertension and four left renal arteries. Superiorand inferior-most renal arteries were normal, whereas second-most-superior artery was severely stenotic (not shown). Selective catheter-based angiographic image shows that third-most-superior renal artery provides collateral blood flow (arrowheads) to poststenotic intrarenal portions of second-most-superior renal artery (arrow). Fig year-old girl with hypertension., nteroposterior 3D volume-rendered CT angiography image shows large right renal artery aneurysm (arrows). Renal ostia (arrowheads) are unobstructed. Midportion of right main renal artery is poorly evaluated because of very-highattenuation contrast material in inferior vena cava (asterisks)., Selective catheterization of right main renal artery reveals high-grade focal stenosis (arrow). Contrast material jet (arrowheads) is seen within aneurysm sac. C, More-delayed catheter-based angiographic image shows complete filling of aneurysm sac with contrast material. Right upper pole segmental artery (arrow) is proximally occluded, possibly because of embolic phenomenon, and there is distal reconstitution from inferior adrenal artery branches (arrowheads). JR:200, June 2013 W669

10 Castelli et al. C Fig year-old boy with hypertension and neurofibromatosis type 1. and, nteroposterior 3D volume-rendered CT angiography () and catheter-based angiography () images show numerous areas of bilateral renal artery narrowing and aneurysm formation (arrows). Superior mesenteric artery (arrowheads) is also abnormally dilated with focal aneurysm formation. C, xial CT angiography image shows extensive cortical scarring of left kidney (arrow), possibly due to embolic phenomenon. Fig year-old girl with hypertension due to Takayasu arteritis. nteroposterior 3D volumerendered MR angiography image shows severe bilateral renal artery ostial stenosis (arrows). Mild narrowing of distal abdominal aorta is also likely present. W670 JR:200, June 2013

11 Renin-Mediated Hypertension in Children Fig year-old boy with hypertension after undergoing radiation therapy for neuroblastoma. and, Coronal () and sagittal () reformatted CT angiography (CT) images show focal complete aortic occlusion (arrows, and ) with reconstitution via mesenteric collateral vessels (arrowheads, ). Superior mesenteric artery stent is patent. There are also radiation-induced vertebral body changes (asterisks, ). C, xial CT image shows marked atrophy of right kidney (asterisk) and occluded right renal artery stent (arrow). Remaining perfusion of right kidney is via collateral circulation. C C Fig year-old girl with hypertension and neuroblastoma. and, xial subvolume maximum-intensity-projection CT angiography (CT) images show large retroperitoneal mass (asterisks) engulfing abdominal aorta and renal arteries, with resultant marked stretching and narrowing of renal arteries (arrows). C, Coronal reformatted CT image shows global hypoperfusion of right kidney (arrowheads). JR:200, June 2013 W671

12 Castelli et al. Fig year-old boy with neurofibromatosis type 1 and persistent hypertension after recent aortoplasty with left renal artery reimplantation. nteroposterior 3D volume-rendered MR angiography image shows left renal artery narrowing due to mass effect from adjacent abdominal aortic pseudoaneurysm (arrow). There are postsurgical changes involving infrarenal abdominal aorta (aortoplasty), and right kidney is surgically absent. W672 JR:200, June 2013