Diagnosis of Renal Arteriovenous Malformation using 64-row Multiple Detector Computed Tomography and Computed Tomography Angiography

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1 中華放射醫誌 Chin J Radiol 200; 35: Diagnosis of Renal Arteriovenous Malformation using 64-row Multiple Detector Computed Tomography and Computed Tomography Angiography Shi-Zuo Liu Tzu-Lung Ho Soa-Min Hsu Hui-Lun Zhan Chen-Pin Chou 2,3 Department of Radiology, Kuang Tien General Hospital Department of Radiology 2, Kaohsiung Veterans General Hospital Institute of Clinical Medicine 3, National Yang-Ming University A 47-year-old woman presented to our hospital with chief complaints of hematuria and left flank pain. The patient denied any recent history of trauma, renal surgery or urinary tract disease. Arterial-phase CT and three-dimensional CT angiography were performed by 64-row multiple detector computed tomography (64-MDCT) and manufacturer-provided workstation. Tortuous fistulas close to the collecting system between the branches of left renal artery and vein were found on arterial phase 64-MDCT and CT angiography. The diagnosis of cirsoid renal arteriovenous malformation (AVM) was made according to CT imaging findings. The patient underwent conventional angiography and transcatheter arterial embolization for renal AVM. She remained symptom free at three-month clinical follow-up. Hematuria is a clinical commonly encountered symptom of diverse urinary tract disorders, including renal or ureteral calculus, uroepithelial neoplasms, trauma, infection and renal vascular diseases []. Among the differential diagnoses of hematuria, renal vascular diseases are extremely rare and difficult diagnoses. Clinicians sometimes fail to diagnose and delay treatment of renal vascular diseases. Non-invasive imaging modalities, including intravenous urography (IVU), ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI), are commonly used to diagnose urinary tract diseases []. Most of imaging modalities have their limitation in the evaluation of a renal vascular lesion. With the recent development of 64-row multiple detector computed tomography (64-MDCT) and reformatted CT angiography (CTA) images, various vascular diseases can be easily demonstrated [2]. We presented a rare case of renal arteriovenous malformation (AVM) and its imaging findings at 64-MDCT and CTA. CASE REPORT Reprint requests to: Dr. Chen-Pin Chou Department of Radiology, Kaohsiung Veterans General Hospital. No. 386, Ta Chung st Road, Kaohsiung 83, Taiwan, R.O.C. A 47-year-old woman presented to our hospital with a chief complaint of left flank pain for three days. She also complained of intermittent gross hematuria for several weeks. Physical examination and vital signs were unremarkable. Laboratory examination revealed anemia with a hematocrit of 22.6% and hemoglobin of 7.7 g/dl. Urinalysis showed hematuria (RBC: numerous/hpf, WBC: 5/HPF). The patient denied any recent history of trauma, renal surgery or urinary tract infection. Under suspicion of renal stone or urinary tract tumor, she was admitted for further work-up.

2 MDCT and CTA in diagnosing renal AVM The initial IVU showed relative delay function of the left kidney and a suspicious filling defect in the left pelvocalyceal system. Cystoscopy identified a large amount of blood clot lodged in the urinary bladder and left ureteral orifice. Non-enhanced CT (NECT) and dual-phase contrast-enhanced CT (CECT) was performed using the 64-MDCT (Somatom Sensation 64, Siemens AG, Forchheim, Ger many). The t ransverse thin sections were analyzed on a workstation (Syngo, Siemens) with manufacturer-provided software that allows generation of two-dimension and three-dimension volumerendered images. The NECT demonstrated left side hydronephrosis with high-density blood clots in the left renal pelvis. The arterial-phase CECT images (Fig. a-b) and three-dimensional reformatted CTA (Fig. c) identified tortuous fistulas close to the collecting system between the branches of left renal artery and vein, and the diagnosis of cirsoid renal AVM was suggested. The patient underwent conventional renal angiography for further interventional therapy. Digital subtraction angiography images revealed multiple small tortuous fistulas between segmental renal arteries and veins (Fig. 2a). Transcatheter arterial embolization of the renal AVM was performed with coils and the follow-up angiography confirmed successful embolization (Fig. 2b). The patient Figure. a-c: Imaging of renal AVM using 64-MDCT. a-b. Axial view and reformatted sagittal images of the arterialphase CT reveals abnormal enhancing vascular lesions (arrow) close to left renal pelvocalyceal system. c. The renal CTA with volume-rendered technique demonstrates multiple renal vascular fistulas, the renal AVM nidus (arrows) and early enhancing left renal vein (arrowhead).

3 64-MDCT and CTA in diagnosing renal AVM 223 remained symptom free at three-month clinical follow-up. DISCUSSION Abnor mal renal vascular communications between the intrarenal arterial and venous systems may be described as renal arteriovenous fistula or renal AVM [3, 4]. Renal AVM is rare and accounts for less than one-quarter of all renal vascular abnormalities, with an incidence of less than 0.04% [5]. Renal AVM is either congenital or acquired (often by iatrogenic procedures). The clinical symptoms include hematuria, systolic hypertension, and flank pain. Hematuria is the most common initial clinical symptom of renal AVM [6]. Renal AVM can also cause increased systemic venous return, which results in high-output heart failure [7]. Congenital renal AVM can be classified as cirsoid, angiomatous or aneurysmal type [8]. The diagnosis of cirsoid renal AVM should fulfill certain criteria, including no history of renal injury or disease, typical angiographic findings, and tortuous vascular channels between segmental or interlobar renal ar teries and veins [7]. The tor tuous and hypertensive vessels, the so-called nidus, are located immediately beneath the urothelium and often cause clinical symptoms of flank pain or hematuria. It is believed that aneurysmal renal AVM arises from a congenital renal arterial aneurysm, which expands and eventually erodes into adjacent renal vein. Sometimes, intraluminal thrombus could be found within dilated vessels. Most acquired renal AVMs are small, asymptomatic, and close spontaneously. Therapeutic intervention is indicated when persistent hematuria or rupture of the renal AVM occurs. Imaging tools can detect most of renal parenchymal or urinary tract diseases causing hematuria. Traditionally, IVU and retrograde pyelography are used as first line methods to evaluate urinary mucosa lesions or urolithiasis. US is a convenient tool for detect renal parenchyma malignancy or obstructive uropathy. Color Doppler US has been shown to be more effective for patients with renal vascular diseases [9]. Color Doppler US has advantage of low cost, non-invasive nature, and wide availability. However, the commonly encountered problems with Color Doppler US are operator dependence, limited usage for patients with fat figure, and sometime equivocal diagnosis. 2a Figure 2. a-b: Conventional angiography and transcatheter arterial embolization of renal AVM. a. Conventional arteriography of the left renal artery demonstrate two nidus (arrows), which are composed of multiple small vascular fistulous connections between segmental or interlobar renal arteries and veins. b. Transcatheter arterial embolization of the left renal AVM with two metallic coils (arrows) was done smoothly. The follow-up angiography shows disappearance of renal AVM. 2b

4 MDCT and CTA in diagnosing renal AVM NECT can detect blood clots in collecting system, renal parenchyma or vascular wall calcifications, and urolithiasis. CECT can identify renal parenchyma abnormalities and uroepithelial lesions that cause hematuria. Arterial-phase CT images of renal AVM show typical early enhancement of vascular abnormalities and are different from common renal malignancies [0]. The arterial-phase CECT is valuable in differential diagnosis between renal malignancy and vascular lesion. An arterialphase CECT depends on the optimized ar terialphase scanning timing, volume and injection rate of contrast agent [, 2]. A diminished focal renal enhancement or cortical atrophy distal to the renal AVM may be due to vascular shunting [0]. Early visualization of the ipsilateral renal vein and inferior vena cava are valuable signs of AVM [7]. CECT has disadvantages of iodinated contrast agent allergy and relative higher radiation dose due to multiplephase scanning [2]. Vascular lesions of kidney can be overlooked due to thick-sliced images or inappropriate scanning time. A flow void in renal MRI will raise the suspicion of a renal vascular lesion [6]. MR angiography of renal AVM may identify tangles of engorged vascular structures, fistulas, and early enhancement of the ipsilateral renal vein as well as suprarenal inferior vena cava [3]. Conventional angiography has been a standard procedure for determining the precise location, extent of lesion, feeding and draining vessels of renal AVM [7]. Conventional angiography has disadvantages of being invasive, causing suffering from procedures, and less renal parenchyma information compared with CT or MRI. I n the past, par tial or tot al neph rectomy combined with arterial reconstructive procedures was the most common procedure of renal AVM. Surgery for renal AVM required extensive dissection of renal arterial branches with high-risk of renal parenchymal damage or even radical nephrectomy [4]. Currently, transcatheter arterial embolization is the treatment of choice for symptomatic renal AVM. Transcatheter arterial embolization can preserve a maximum amount of normal renal parenchyma while eliminating the abnormal renal vascular structures [5]. Recent advances of 64-MDCT technology have great advantage of thin slice images for isotropic image, less scanning time, and covering entire urinary tract from kidney to urinary bladder. In this case, the thin-sliced MDCT images and CTA can well demonstrate the features of a renal AVM, including multiple renal vascular fistulas (nidus) located immediately beneath the urothelium and early enhancing ipsilateral renal vein. With optimized contrast agent injection technique, CTA could generate screening reformatted CTA images like conventional angiography. REFERENCES. 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: Liu SZ, Hsu SM, Zhan HL, Wu MT. Right aortic arch with mirror-image branching in an asymptomatic adult: a rare case demonstrated with 64-detector computed tomography. Chin J Radiol 2008; 33: Subramanyam BR, Lefleur RS, Bosniak MA. Renal arteriovenous fistulas and aneurysm: sonographic findings. Radiology 983; 49: Monin RD, Dunn EJ, Wright CB. Renal arteriovenous fistulas: a review of etiology, diagnosis, and management. Surgery 986; 99: Cho KJ, Stanley JC. Non-neoplastic congenital and acquired renal arteriovenous malformations and fistulas. Radiology 978; 29: Rak KM, Yakes WF, Ray RL, et al. MR imaging of symptomatic peripheral vascular malformations. AJR Am J Roentgenol 992; 59: Crotty KL, Orihuela E, Warren MM. Recent advances in the diagnosis and treatment of renal arteriovenous malformations and fistulas. J Urol 993; 50: Cura M, Elmerhi F, Suri R, Bugnone A, Dalsaso T. Vascular malformations and arteriovenous fistulas of the kidney. Acta Radiol 200; 5: King BF, Hattery RR. Congenital cirsoid renal arteriovenous malformation (AVM) involving the lower pole of the right kidney. Radiographics 990; 0: Bhatt S, MacLennan G, Dogra V. Renal pseudotumors. AJR Am J Roentgenol 2007; 88: Kawashima A, Sandler CM, Ernst RD, Tamm EP, Goldman SM, Fishman EK. CT evaluation of renovascular disease. RadioGraphics 2000; 20: Honda H, Onitsuka H, Naitou S, et al. Renal arteriovenous malformations: CT features. J Comput Assist Tomogr 99; 5: Hong YC, Chou CT, Lee KW. Magnetic resonance imaging of renal arteriovenous malformation: a case report. Chin J Radiol 2007; 32: Regan JB, Benson RC. Congenital renal arteriovenous malformations. J Urol 986; 36: Defreyne L, Govaere F, Vanlangenhove P, Derie A, Kunnen M. Cirsoid renal arteriovenous malformation treated by endovascular embolization with n-butyl 2-cyanoacrylate. Eur Radiol 2000; 0:

5 64-MDCT and CTA in diagnosing renal AVM 225 利用 64 排多切面電腦斷層及電腦斷層血管影像診斷腎動靜脈畸形 劉時佐 何子龍 徐守民 詹慧倫 周春平 2,3 光田綜合醫院放射線科 高雄榮民總醫院放射線部 2 國立陽明大學臨床醫學研究所 3 一名 47 歲的婦女主訴血尿和左側背痛至醫院求診 患者否認有最近的創傷 腎臟手術或者尿道疾病的病史 在 64 排多切面電腦斷層執行動脈相電腦斷層並使用製造商提供的工作站做出三維電腦斷層血管影像 在動脈相 64 排多切面電腦斷層與重組的電腦斷層血管影像發現左腎緊鄰著泌尿收集系統, 在動脈分支與靜脈之間有彎曲的血管 依據電腦斷層影像的結果而做出曲張性腎臟動靜脈畸形的診斷 這名患者接受了傳統血管攝影檢查及經導管動脈栓塞治療腎臟動靜脈畸形 她在後續 3 個月的臨床追蹤中, 依然沒有症狀