MULTIDETECTOR ROW COMPUTED TOMOGRAPHY AND ULTRASOUND CHARACTERISTICS OF CAUDALVENA CAVA DUPLICATION IN DOGS GIOVANNA BERTOLINI,ALESSIA DIANA,MARIO CIPONE,MICHELE DRIGO,MARCO CALDIN Caudal vena cava duplication has been rarely reported in small animals. The purpose of this retrospective study was to describe characteristics of duplicated caudal vena cava in a large group of dogs. Computed tomography (CT) and ultrasound databases from two hospitals were searched for canine reports having the diagnosis “double caudal vena cava.” One observer reviewed CT images for 71 dogs and two observers reviewed ultrasound images for 21 dogs. In all CT cases, the duplication comprised two vessels that were bilaterally symmetrical and approximately the same calibre (similar to Type I complete duplication in humans). In all ultrasound cases, the duplicated caudal vena cava appeared as a distinct vessel running on the left side of the abdominal segment of the descending aorta and extending from the left common iliac vein to the left renal vein. The prevalence of caudal vena cava duplication was 0.46% for canine ultrasound studies and 2.08% for canine CT studies performed at these hospitals. Median body weight for affected dogs was significantly lower than that of unaffected dogs (P < 0.0001). Breeds with increased risk for duplicated caudal vena cava were Yorkshire Terrier (odds ratio [OR] = 6.41), Poodle (OR = 7.46), West Highland White Terrier (OR = 6.33), and Maltese (OR = 3.87). Presence of a duplicated caudal vena cava was significantly associated with presence of extrahepatic portosystemic shunt(s) (P < 0.004). While uncommon in dogs, caudal vena cava duplication should be differentiated from other vascular anomalies when planning surgeries and for avoiding misdiagnoses. C  2014 American College of Veterinary Radiology. Key words: CT, dog, embryology, ultrasound, vena cava. Introduction I N MAMMALS, THE CAUDAL vena cava is formed from a complex process involving development, regression, anastomoses, and replacement of three pairs of embryonic vessels, namely the supracardinal, subcardinal, and vitelline veins. 1–3 The presence of two cava veins in the abdomen most commonly results from persistence of the two embry- onic supracardinal veins. 4–6 A double caudal vena cava is a normal arrangement in whales and dolphins, and has been reported as an uncommon variant in humans 7 and domes- tic animals. 4–6 In humans, prevalence for duplication of the inferior vena cava has been reported to be 0.2–3%. Du- plication, as well as other anomalies of the inferior vena cava, has been reported to be a risk factor for develop- ment of deep vein thrombosis. 7–10 Awareness of abnormal retroperitoneal vessels has been reported to be important From the “San Marco Private Veterinary Clinic”, via Sorio 114/c, 35141, Padua, Italy (Bertolini , Caldin), Veterinary Clinical Depart- ment, Faculty of Veterinary Medicine, University of Bologna, Via Tolara di Sopra, 50 Ozzano dell’Emilia, Italy (Diana, Cipone), and Depart- ment of Animal Medicine, Production and Health, University of Padua, Viale dell’Universit` a, 35020, Legnaro, Italy (Drigo). Address correspondence and reprint requests to Giovanna Bertolini, at the above address. E-mail: bertolini@sanmarcovet.it Received November 4, 2013; accepted for publication January 15, 2014. doi: 10.1111/vru.12162 for avoiding diagnostic pitfalls and intraoperative compli- cations during surgical or interventional procedures. 11–13 Duplication of the caudal vena cava has been rarely re- ported in small animals. For reported cases, the anomaly has been primarily described as an incidental finding dur- ing imaging for other reasons and has been associated with other congenital anomalies. 14–17 To the authors’ knowledge, a large-scale study of this vascular anomaly has not been reported in dogs. The pur- pose of this retrospective study was to describe the preva- lence, patterns, and associated imaging features of caudal vena cava duplication in a group of dogs presented for ab- dominal ultrasound (US) or multidetector-row computed tomography (MDCT) examinations. Material and Methods Selection of MDCT Cases A computerized search of an MDCT reports database was performed for enhanced abdominal MDCT obtained at the “San Marco” Veterinary Clinic from March 2006 to December 2012, to identify patients with duplication of the caudal vena cava. The MDCT reports database runs Vet Radiol Ultrasound, Vol. 55, No. 5, 2014, pp 521–530. 521