Radiology Page
Renal Arteriovenous Malformation A 77-year-old male presented with hematuria. Noncontrast computerized tomography (CT) showed small renal calculi and a large tubular structure in the right renal hilum suggestive of a renal vascular anomaly. Multiphase CT angiography subsequently confirmed the presence of a large right renal hilar arteriovenous malformation (AVM) (see figure).
Renal vascular malformations, classified as arteriovenous fistula (AVF) or arteriovenous malformation, are aberrant communications between the renal arterial and venous systems.1 The majority of renal vascular abnormalities are AVFs, with AVMs occurring in less than 1% of the general population.1,2
Incidentally discovered renal AVM on contrast enhanced CT of abdomen. Axial image from arterial (a) and nephrogram (b) phases, and coronal image from arterial (c) and nephrogram (d ) phases. Note large tortuous cluster of vessels (arrows) in right renal hilum. Density mirrors abdominal aorta on both scan phases.
0022-5347/14/1914-1128/0 THE JOURNAL OF UROLOGY® © 2014 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
1128
j
www.jurology.com
AND
RESEARCH, INC.
http://dx.doi.org/10.1016/j.juro.2014.01.003 Vol. 191, 1128-1129, April 2014 Printed in U.S.A.
RADIOLOGY PAGE
Renal AVFs comprise 70% to 80% of anomalous renal vascular communications.3 They are generally acquired as a consequence of direct traumatic injury, such as a renal biopsy or penetrating trauma, or they can develop from renal or retroperitoneal malignancy, or inflammation.1 The incidence of renal AVFs after percutaneous renal biopsy has been reported as high as 18%.1 As opposed to AVMs, renal AVFs have a single direct communication between the renal artery and vein. The majority of patients with AVFs are asymptomatic with the most common clinical manifestation being an abnormal bruit.3 Fewer than 10% of patients with an AVF present with gross hematuria.1 The vast majority of AVFs resolve spontaneously.1 In contradistinction, renal AVMs are primarily congenital and typically found incidentally at diagnostic imaging.3 They are comprised of a bundle of complex, tortuous dilated vessels developed from an abnormal connection between the renal artery and vein via a vascular nidus.2 Vascular nidi are subdivided into cirsoid, angiomatous and anuerysmal types. The most common type, cirsoid, consists of multiple, enlarged arterial feeders interconnecting with draining veins.1 The angiomatous variant is from a single arterial feeder to several draining veins. The aneurysmal type is typically centered in the renal hilum and has a single artery connected to a single vein with aneurysmal dilatation.1,2 Patients with AVMs most commonly present with hematuria due to rupture of small venules into the renal collecting system from increased intravascular pressure.2 Approximately a third of patients may present with signs of congestive heart failure, and up to half have symptoms of cardiomegaly and hypertension.4 Catheter angiography is the gold standard for visualization and treatment of renal vascular abnormalities.1 The ability of catheter angiography to selectively opacify small arterial branches and accurately evaluate multiple feeder vessels aids in confirmation or exclusion and treatment of the abnormality.2 However, noninvasive imaging is more commonly used to establish the diagnosis of renal AVF or AVM. The low cost, easy accessibility and noninvasive nature of color Doppler ultrasonography makes it an ideal imaging modality for screening patients for a suspected AVF or AVM.1,5 On gray scale ultrasound imaging, renal vascular malformations appear as a bundle of hypoechoic vessels of diverse caliber.5 Color Doppler demonstrates turbulent, mosaic patterned blood flow.5 A disadvantage of ultrasonography is poor sensitivity to a small central renal AVF due to difficulty distinguishing it from the normal renal artery and vein.5
1129
CT can play a role in evaluating renal AVM and AVF. Unenhanced scans will primarily show an intrarenal or perinephric mass with blood attenuation and overlying renal cortical atrophy.5 On contrast enhanced CT, arterial phase will demonstrate a vascular attenuation mass in the renal sinus with prompt filling of the renal vein and inferior vena cava.5 Decreased enhancement of normal renal parenchyma may occur due to shunting effects. Delayed or nephrogram phase images commonly show the renal AVM with similar attenuation as the aorta and suprarenal inferior vena cava with dilatation of the renal and left gonadal veins.5 Magnetic resonance imaging can also be used to diagnose vascular malformations. Although it shows major feeding vessels and multiple intralesional vessels in high flow lesions, these features may be absent in low flow lesions without the use of intravenous contrast. Magnetic resonance imaging is more expensive and does not provide the real-time flow dynamics seen on ultrasound.5 The primary choice for treatment of renal AVM and AVF is catheter embolization because it minimizes damage to the renal parenchyma.1,6 The goal of embolization is complete occlusion of the nidus in the AVM and feeder artery in the AVF.1,6 Various embolic agents include absolute ethanol, polyvinyl alcohol and n-butyl-2-cyanoacrylate. Other less common treatment options include radio frequency ablation and coil embolization.2,6 Surgery is generally reserved for cases when endovascular treatment is deemed too risky, has failed or is associated with malignancy.1 In our patient CT angiography was sufficient to confirm the diagnosis of AVM. The patient elected conservative management of the AVM with surveillance. Haq Wajid and Brian R. Herts Imaging Institute Cleveland Clinic Cleveland, Ohio 1. Cura M, Elmerhi F, Suri R et al: Vascular malformations and arteriovenous fistulas of the kidney. Acta Radiol 2010; 51: 144. 2. Chimpiri AR and Natarajan B: Renal vascular lesions: diagnosis and endovascular management. Semin Intervent Radiol 2009; 26: 253. 3. Kawashima A, Sandler CM, Ernst RD et al: CT evaluation of renovascular disease. RadioGraphics 2000; 20: 1321. 4. Iwazu Y, Muto S, Miyata Y et al: The origin of idiopathic renal arteriovenous malformation with giant twin aneurysms. Clin Nephrol 2013; 79: 81. 5. Muraoka N, Sakai T, Kimura H et al: Rare causes of hematuria associated with various vascular diseases involving the upper urinary tract. RadioGraphics 2008; 28: 855. 6. Zhang B, Jiang ZB, Huang MS et al: The role of transarterial embolization in the management of hematuria secondary to congenital renal arteriovenous malformations. Urol Int 2013; 91: 285.
Renal Arteriovenous Malformation A 77-year-old male presented with hematuria. Noncontrast computerized tomography (CT) showed small renal calculi and a large tubular structure in the right renal hilum suggestive of a renal vascular anomaly. Multiphase CT angiography subsequently confirmed the presence of a large right renal hilar arteriovenous malformation (AVM) (see figure).
Renal vascular malformations, classified as arteriovenous fistula (AVF) or arteriovenous malformation, are aberrant communications between the renal arterial and venous systems.1 The majority of renal vascular abnormalities are AVFs, with AVMs occurring in less than 1% of the general population.1,2
Incidentally discovered renal AVM on contrast enhanced CT of abdomen. Axial image from arterial (a) and nephrogram (b) phases, and coronal image from arterial (c) and nephrogram (d ) phases. Note large tortuous cluster of vessels (arrows) in right renal hilum. Density mirrors abdominal aorta on both scan phases.
0022-5347/14/1914-1128/0 THE JOURNAL OF UROLOGY® © 2014 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
1128
j
www.jurology.com
AND
RESEARCH, INC.
http://dx.doi.org/10.1016/j.juro.2014.01.003 Vol. 191, 1128-1129, April 2014 Printed in U.S.A.
RADIOLOGY PAGE
Renal AVFs comprise 70% to 80% of anomalous renal vascular communications.3 They are generally acquired as a consequence of direct traumatic injury, such as a renal biopsy or penetrating trauma, or they can develop from renal or retroperitoneal malignancy, or inflammation.1 The incidence of renal AVFs after percutaneous renal biopsy has been reported as high as 18%.1 As opposed to AVMs, renal AVFs have a single direct communication between the renal artery and vein. The majority of patients with AVFs are asymptomatic with the most common clinical manifestation being an abnormal bruit.3 Fewer than 10% of patients with an AVF present with gross hematuria.1 The vast majority of AVFs resolve spontaneously.1 In contradistinction, renal AVMs are primarily congenital and typically found incidentally at diagnostic imaging.3 They are comprised of a bundle of complex, tortuous dilated vessels developed from an abnormal connection between the renal artery and vein via a vascular nidus.2 Vascular nidi are subdivided into cirsoid, angiomatous and anuerysmal types. The most common type, cirsoid, consists of multiple, enlarged arterial feeders interconnecting with draining veins.1 The angiomatous variant is from a single arterial feeder to several draining veins. The aneurysmal type is typically centered in the renal hilum and has a single artery connected to a single vein with aneurysmal dilatation.1,2 Patients with AVMs most commonly present with hematuria due to rupture of small venules into the renal collecting system from increased intravascular pressure.2 Approximately a third of patients may present with signs of congestive heart failure, and up to half have symptoms of cardiomegaly and hypertension.4 Catheter angiography is the gold standard for visualization and treatment of renal vascular abnormalities.1 The ability of catheter angiography to selectively opacify small arterial branches and accurately evaluate multiple feeder vessels aids in confirmation or exclusion and treatment of the abnormality.2 However, noninvasive imaging is more commonly used to establish the diagnosis of renal AVF or AVM. The low cost, easy accessibility and noninvasive nature of color Doppler ultrasonography makes it an ideal imaging modality for screening patients for a suspected AVF or AVM.1,5 On gray scale ultrasound imaging, renal vascular malformations appear as a bundle of hypoechoic vessels of diverse caliber.5 Color Doppler demonstrates turbulent, mosaic patterned blood flow.5 A disadvantage of ultrasonography is poor sensitivity to a small central renal AVF due to difficulty distinguishing it from the normal renal artery and vein.5
1129
CT can play a role in evaluating renal AVM and AVF. Unenhanced scans will primarily show an intrarenal or perinephric mass with blood attenuation and overlying renal cortical atrophy.5 On contrast enhanced CT, arterial phase will demonstrate a vascular attenuation mass in the renal sinus with prompt filling of the renal vein and inferior vena cava.5 Decreased enhancement of normal renal parenchyma may occur due to shunting effects. Delayed or nephrogram phase images commonly show the renal AVM with similar attenuation as the aorta and suprarenal inferior vena cava with dilatation of the renal and left gonadal veins.5 Magnetic resonance imaging can also be used to diagnose vascular malformations. Although it shows major feeding vessels and multiple intralesional vessels in high flow lesions, these features may be absent in low flow lesions without the use of intravenous contrast. Magnetic resonance imaging is more expensive and does not provide the real-time flow dynamics seen on ultrasound.5 The primary choice for treatment of renal AVM and AVF is catheter embolization because it minimizes damage to the renal parenchyma.1,6 The goal of embolization is complete occlusion of the nidus in the AVM and feeder artery in the AVF.1,6 Various embolic agents include absolute ethanol, polyvinyl alcohol and n-butyl-2-cyanoacrylate. Other less common treatment options include radio frequency ablation and coil embolization.2,6 Surgery is generally reserved for cases when endovascular treatment is deemed too risky, has failed or is associated with malignancy.1 In our patient CT angiography was sufficient to confirm the diagnosis of AVM. The patient elected conservative management of the AVM with surveillance. Haq Wajid and Brian R. Herts Imaging Institute Cleveland Clinic Cleveland, Ohio 1. Cura M, Elmerhi F, Suri R et al: Vascular malformations and arteriovenous fistulas of the kidney. Acta Radiol 2010; 51: 144. 2. Chimpiri AR and Natarajan B: Renal vascular lesions: diagnosis and endovascular management. Semin Intervent Radiol 2009; 26: 253. 3. Kawashima A, Sandler CM, Ernst RD et al: CT evaluation of renovascular disease. RadioGraphics 2000; 20: 1321. 4. Iwazu Y, Muto S, Miyata Y et al: The origin of idiopathic renal arteriovenous malformation with giant twin aneurysms. Clin Nephrol 2013; 79: 81. 5. Muraoka N, Sakai T, Kimura H et al: Rare causes of hematuria associated with various vascular diseases involving the upper urinary tract. RadioGraphics 2008; 28: 855. 6. Zhang B, Jiang ZB, Huang MS et al: The role of transarterial embolization in the management of hematuria secondary to congenital renal arteriovenous malformations. Urol Int 2013; 91: 285.
