The Independent Right and Left Azygos Veins with Hemiazygos Absence: A Rare Case Presentation

The veins of the azygos system vary greatly in mode of origin, course, numbers of tributaries and anastomoses, and nature of termination. The azygos vein system can take different courses. Such variation is important in mediastinal surgery, and knowledge of congenital variations can be of clinical importance. It is imperative for reporting radiologists to identify such anomalies. 1. Background The azygos venous system largely replaces the postcardinal veins of the embryo; portions of the primitive veins persist only at the commencement of the azygos system [1, 2]. Many systemic variations occur because of the complex embryologic development of the veins [2, 3]. The thoracic portion of the azygos venous system is subject to especially wide variation [2, 4–6]. These variations are important in surgical, radiological, and clinical terms. It is thus helpful to recognize the presence of variations so that computed tomography (CT) data may be properly interpreted. We present a rare case of independent right and left azygos veins, with absence of the hemiazygos, in a 52-year-old woman. 2. Case Presentation A 52-year-old woman was admitted to our institution with a three-hour history of chest pain expanding to the neck and left arm. Palpitation and fatigue were present. Negative T-waves were evident upon ECG. Upon echocardiography, an aneurysmatic dilatation was found in the origin of the ascending aorta. Thoracic CT angiography was performed using a 64-channel multidetector scanner (SOMATOM Sensation 64; Siemens, Erlangen, Germany) and the following scanning parameters: 0.6？mm collimation, 0.8？mm slice thickness, 1.4？mm increment, 100？kV, 135？mA, pitch of 0.9, and a gantry rotation time of 0.33？s. A scout image was acquired while the patient was in the supine position, and the region from the level of the aortic arch to the diaphragm was examined in detail. The patient was given 100？mL of nonionic contrast medium (Ultravist 300; Bayer Schering Pharma, Berlin, Germany) via a catheter placed into the right antecubital vein, at a flow rate of 5？mL/s, using an automated injector. The scan was performed 20？s after commencement of injection. The diameter of the ascending aorta was approximately 63？mm. An aneurysmatic ascending aorta had exerted pressure on the superior vena cava (Figure 1). The right azygos vein discharged the superior vena cava (Figure 2). However, no left hemiazygos vein was present. A left azygos vein discharged the left subclavian vein (Figures 3, 4, 5, and 6). Figure 1: The aneurysmatic ascending aorta had pressured the superior vena cava