Transarterial Coil Embolization of an Abdominal Aortocaval Fistula in a Dog

Abstract

A 3-year-old, 5 kg, male Toy Poodle with a mast cell tumor on the left pelvic limb was referred to Tokyo University of Agriculture and Technology Animal Hospital for an oncologic evaluation. On physical examination, a continuous bruit was auscultated over the left inguinal region with a palpable thrill. Cardiac auscultation identified a grade II/VI systolic and a grade I/VI diastolic murmur over the mitral and the aortic valves, respectively. No signs of peripheral cyanosis or congestion were noted. On thoracic radiographs, moderate, generalized enlargement of the cardiac silhouette was observed without evidence of pulmonary edema or pleural effusion. Color Doppler echocardiography identified mild pulmonic, mitral, and aortic valve regurgitation. Measurements of the left ventricle (LV) indicated an increased internal diameter with normal LV wall and septal thicknesses, normal fractional shortening and mild left atrial (LA) enlargement, with normal sinus rhythm. Normal mean arterial blood pressure was obtained on the thoracic limb using the oscillometric method. Laboratory test results (complete blood count, serum biochemistry profile, electrolytes, coagulation profile) were within the normal reference ranges. Ultrasonography of the caudal abdomen showed a caudal vena cava (CVC) with a diameter of 24.6 mm (dog <10 kg, reference values 0.65 0.12 mm) at the site of shunt. Color Doppler with simultaneous electrocardiogram showed turbulent flow in the CVC during the arterial phase. Continuous-wave Doppler interrogation showed continuous low-velocity flow with a pulsatile pattern and spectral broadening of Doppler waveform and peak flow velocity of 3 m/s across the aortocaval shunt (Fig 1). Contrast-enhanced computed tomography (CT) was performed under general anesthesia for anatomic evaluation of the arteriovenous shunt. The contrast timing bolus method was used to synchronize image acquisition. Iodinated contrast medium (2 mL/kg of iodine) was injected into the cephalic vein at flow rate of 1 mL/s. After a 20-second delay, the entire abdomen was scanned with a dual-slice spiral CT scanner. Reconstruction was carried out using contiguous images with a slice thickness of 1.0 mm (total of 149 slices). Post imaging processing showed an aortocaval connection by an anomalous vessel (shunt) located caudal to the renal arteries and a saccular dilatation of the CVC elongating in the caudal direction. The major dilatation was observed caudal to the fistula, 2.6-fold greater than the dilatation observed cranial to the fistula (Fig 2A,B). Endovascular repair was performed under general anesthesia that was maintained with isoflurane. The dog was positioned in right lateral recumbency for a cervical left lateral approach and a small incision in the skin was made to access the left common carotid artery. A 4-Fr multipurpose catheter was inserted through a puncture in the artery and advanced over a guide wire. The catheter tip was positioned in the abdominal aorta, cranial to the fistula to perform aortography. A 5-mL bolus injection of iodinated contrast medium showed the contrast medium being diverted from the aorta into the CVC (Fig 3A). Blood flow in the renal arteries was preserved as observed by contrast filling of the arteries and renal excretion. The tip of the catheter then was repositioned into the AVF over a guide wire to deliver the embolization coil, because contrast injection showed that adequate coil deployment could be achieved through the aorta. An embolization coil of 6.5 mm diameter, 5 loops, and 10 cm in length was deployed along the fistula lumen under fluoroscopic guidance. Aortography a few minutes after coil deployment identified residual flow through the fistula (Fig 3B). Residual flow was also observed on Doppler ultrasonography, but the shunt flow velocity had decreased to 1.5 m/s. Recovery from the anesthesia was uneventful. Postoperative mean arterial blood pressure ranged from From the Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan (Nakata, Tanaka, Hamabe, Yoshiyuki, Kim, Suzuki, Aytemiz, Huai-Che, Shimizu, Fukushima). Corresponding author: Ryou Tanaka, DVM, PhD, Department of Veterinary Surgery, Tokyo University of Agriculture and Technology, Saiwai-cho 3-5-8, Fuchu, Tokyo 183-8509, Japan; e-mail: ryo@vet.ne.jp. Submitted May 17, 2013; Revised November 19, 2013; Accepted December 16, 2013. Copyright © 2014 by the American College of Veterinary Internal Medicine 10.1111/jvim.12308 Abbreviations: