British Journal of Radiology (2004) 77, 342-343
© 2004 British Institute of Radiology
doi: 10.1259/bjr/28611372
Partial thrombosis of an idiopathic azygos vein aneurysm
M-A Gomez, MD
1
A Delhommais, MD
1
P F Presicci, MD
2
M Besson, MD
R Roger, MD
1 and
D Alison, MD
1
Departments of 1 Radiology and 2 Thoracic Surgery, Trousseau Hospital, Medical School University of Tours, 37044 Tours Cedex France
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Abstract
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Aneurysms of the azygos vein are often asymptomatic, detected on a chest radiograph simulating paratracheal mass. When the aneurysm is totally thrombosed, it is impossible to distinguish it from another cause of mediastinal mass. A case is presented in which partial thrombosis of the aneurysm and communication with the superior vena cava led to a diagnosis on angiography and CT.
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Introduction
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Idiopathic aneurysms of the azygos vein are uncommon: 30 cases have been reported in the literature, often incidentally discovered, simulating paratracheal tumours. Theoretically, pulmonary embolism caused by thrombosed aneurysm and rupture of the aneurysm may occur. We report here the first case of radiological illustration of a partially thrombosed idiopathic azygos vein aneurysm.
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Case report
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A 20-year-old man underwent chest radiography because he complained of recent chest pain. He had been admitted 5 days beforehand for investigation of intermittent discomfort beginning with acute loss of right vision, aphasia and right brachiofacial paresis and ending with frontal headache. These symptoms were of a maximum duration of 1 h. Cerebral non-enhanced CT and MRI were normal. The chest radiograph revealed a 6 cm well-defined right paratracheal opacity. Such a mediastinal paratracheal mass suggested a mediastinal tumour, lymphadenopathy, a bronchogenic cyst, an haematoma, extramedullary haematopoiesis or a lung tumour. Differentiation was not possible based upon a chest radiograph alone. Fibrin D Dimer measurement was elevated (2160 ng ml–1) suggesting a thromboembolic process, but this is not a specific test. On non-enhanced CT, the attenuation of the opacity was 72 Hounsfield Units (HU) (Figure 1a
), which did not change on enhanced CT (Figure 1b). Partial intraluminal thrombus of a venous aneurysm was shown on arterial phase-enhanced CT (Figure 1b). Conventional angiography (Figure 2) during the venous phase of the contrast injection showed the thrombosed azygos vein aneurysm, suggesting a communication with the superior vena cava. No aetiology for the malformation was established. Echocardiography was normal and there was no clear explanation of the neurological symptoms. This malformation was thought to be the cause of the recent chest pain. A thoracotomy was performed and revealed a thrombosed azygos vein aneurysm, which was resected. Communication between the superior vena cava and the azygos vein aneurysm was also confirmed. His post-operative course was uncomplicated and his symptoms disappeared.
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Figure 1. (a) Non-enhanced CT of chest shows the opacity with an attenuation of 72 HU. (b) Enhanced CT shows an intraluminal thrombus of azygos vein aneurysm.
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Discussion
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Causes of azygos vein enlargement are: heart failure; obstruction of the inferior vena cava; portal hypertension; and malformations of the inferior vena cava including partial or total agenesis [1]. In such causes, dilatation is related to an increase in blood pressure through the azygos vein. Traumatic pseudoaneurysm may be a differential diagnosis of true aneurysm [2]. A congenital origin of idiopathic aneurysms is suggested, considering that aneurysms could be due to the development of a remnant of an embryological vein that empties into the transverse part of the azygos vein [3].
Aneurysms of the azygos vein are often asymptomatic, detected on a chest radiograph. When the aneurysm is enlarged, it may compress the right main bronchus [4] or the superior vena cava [5].
Radiological features described in previously published cases were reported in the absence of thrombosis. Dynamic enhanced CT, MRI and transoesophageal echography are non-invasive methods, as alternatives to angiography, for suggesting the diagnosis. Dynamic enhanced CT suggests the diagnosis with slight enhancement in the arterial phase and homogeneous enhancement in the late phase [3]. MRI has shown the absence of a flow void in the mass, suggesting a non-vascular mass but in fact indicating a very slow, random flow in the aneurysm caused by a narrow entrance [3]. Transoesophageal echography has shown the anechoic nature of the mass, which was close to the azygos vein [1].
When the aneurysm was totally thrombosed, it was impossible to distinguish it from another cause of mediastinal mass [4]. In our case, partial thrombosis and communication with the superior vena cava led to a diagnosis with enhancement around the thrombus on arterial phase-enhanced CT and angiography. The communication between the superior vena cava and the azygos vein aneurysm could be explained by a congenital origin or by a fistula with the superior vena cava.
Received for publication October 11, 2002.
Revision received May 27, 2003.
Accepted for publication August 20, 2003.
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References
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- Lena H, Desrues B, Hresbach D, Quinquenel M-L, Corbineau H, Rioux C, et al. Azygos vein aneurysm: contribution of transesophageal echography. Ann Thorac Surg 1996;61:1253–5.[Abstract/Free Full Text]
- Jain A, Blebea JS. Post-traumatic pseudoaneurysm of the azygos vein in a patient with azygos continuation. J Comput Assist Tomogr 1994;18:647–8.[Medline]
- Watanabe A, Kusajima K, Aisaka N, Sugawara H, Tsunematsu K. Idiopathic saccular azygos vein aneurysm. Ann Thorac Surg 1998;65:1459–61.[Abstract/Free Full Text]
- Icard P, Fares E, Regnard JF, Levasseur P. Thrombosis of an idiopathic saccular azygos aneurysm. Eur J Cardthorac Surg 1999;15:870–2.
- Seebauer L, Prauer HW, Gmeinwieser J, Sebening F. A mediastinal tumor simulated by a sacculated aneurysm of the azygos vein. Thorac Cardiovasc Surg 1989;37:112–4.[Medline]
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Abstract
Introduction
