Ann Thorac Surg 1998;65:1459-1461
© 1998 The Society of Thoracic Surgeons
Case Reports
Idiopathic Saccular Azygos Vein Aneurysm
Atsushi Watanabe, MDa,
Katsuyuki Kusajima, MDa,
Naohiko Aisaka, MDa,
Hiroyuki Sugawara, MDa,
Kazunori Tsunematsu, MDa
a Department of Thoracic Disease, Hokkaido Tomakomai Domestic Hospital, Tomakomai, Hokkaido, Japan
Accepted for publication December 9, 1997.
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Abstract
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We present a case of asymptomatic saccular aneurysm of the azygos vein. This abnormality is exceedingly rare. Dynamic computed tomography revealed strong enhancement of the mass, suggesting a vascular structure, which was very important for preoperative diagnosis. It is unclear whether the mass should be resected if the preoperative diagnosis has been made and the mass is not so large.
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Introduction
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Aneurysm of the azygos vein is rare. It usually occurs in patients with portal hypertension or venous malformations. Idiopathic saccular aneurysm of the azygos vein is exceedingly rare; only 10 such cases have been reported [1–5]. We incidentally observed this abnormality during evaluation of a cough caused by bronchitis associated with bronchoectasis. Dynamic computed tomography was very important for diagnosing this abnormality.
A 64-year-old-woman was admitted to our hospital for evaluation of cough with a low-grade fever that had continued for 2 months before admission. A chest radiograph taken in the outpatient department showed an abnormal shadow in the right lower lobe. The other radiographic results were normal. Plain chest computed tomography showed mild bronchoectasis in the right lower lobe and the paratracheal mass. Dynamic chest computed tomography revealed a round paratracheal mass 30 mm in diameter and marked enhancement in the back side of the mass in the spine position (Fig 1). Magnetic resonance imaging demonstrated that the mass and azygos vein were contiguous just above the arch, and that the mass had high-intensity and low-intensity areas on a T2-weighted image (Fig 2). Transesophageal echography demonstrated that the mass in close contact with the azygos arch had an anechogenic nature and no Doppler flow in it. These findings indicated that the mass was an azygos vein aneurysm. The patient expressed her desire for the mass to be resected, and a resection was scheduled.
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Fig 1. Dynamic computed tomogram in the spine position showing aneurysm of the azygos vein, 30 mm in diameter, connected to the azygos arch. The back side of the aneurysm is greatly enhanced.
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Fig 2. Magnetic resonance image showing that the mass and azygos vein are contiguous just above the arch and the mass has hyperintense and hypointense areas on a T2-weighted image.
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A right lateral thoracotomy about 10 cm in length was made through the fourth intercostal space. A large saccular aneurysm originating from the azygos arch was observed (Fig 3). There was no evidence of a traumatic cause such as bleeding, adhesions, or fibrosis. The mass was resected with the azygos arch. There was no intraluminal thrombus.
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Fig 3. Intraoperative view showing an azygos vein aneurysm originating from the azygos arch. (Arrowhead = azygos arch; open arrow = superior vena cava; white arrow = aneurysm.)
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Pathologic examination showed that there was a mixture of thin and thick lesions in the aneurysmal wall, and that the thick-walled lesion had hypertrophy of the vascular leiomyocele with fibrosis. No infiltration or accumulation of inflammatory cells was observed.
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Comment
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Aneurysmal dilatation of the azygos vein is uncommon. It usually occurs in patients with portal hypertension, heart failure, malformations of the inferior vena cava including partial or total agenesis, or obstruction of the inferior vena cava by a tumor or other causes [1]. These dilatations are directly related to high blood flow status of the azygos vein system as a collateral. Blunt trauma has also been documented as a cause of aneurysm of the azygos vein. However, in a case of a saccular aneurysm, a remnant of either the right posterior cardinal vein, subcardinal vein, or primitive subclavian vein, which empties into the transverse part of the azygos vein, may be the origin [2].
An azygos vein aneurysm is usually asymptomatic and often detected incidentally on chest radiographs obtained for another purpose. As the aneurysm enlarges, it may lead to pressure effects on adjacent tissues, such as obstruction of the superior vena cava [3] and compression of the right main bronchus or the right upper lobe bronchus. Theoretically, pulmonary thrombosis may be caused by intraluminal thrombus, and rupture of the aneurysm may occur [4].
Kurihara and associates [2] reported that dynamic computed tomography was useful for the diagnosis of azygos vein aneurysm and that there is only slight enhancement of the mass in the early phase but homogeneous enhancement in the late phase on dynamic computed tomographic images. In our case, the saccular mass was greatly enhanced in the early phase at the site near the azygos arch, where there is a high volume of blood flow, but there was little enhancement at the site away from the arch, where there is little blood flow. Thus, the results revealed that there were differences in the amount of blood flow in the mass. Magnetic resonance imaging showed the absence of a flow void in this lesion, initially suggesting a nonvascular structure but in fact indicating a very slow, random flow in the aneurysm caused by a narrow entrance [2]. Lena and associates [1] reported that transesophageal echography was useful for the diagnosis but a Doppler flow was not observed, as we also found in our patient.
An appropriate therapeutic strategy is not clear. Except for the report by Jain and Blebea [6] showing posttraumatic pseudoaneurysm of the azygos vein, there have been no reports of the aneurysm leading to rupture and hemorrhage. Of course, theoretically, the mass may rupture. Although the mass was removed upon the request of the patient in our case, it may not be necessary to remove the mass if the azygos vein aneurysm can be diagnosed before the operation and if the size of aneurysm is not so large. Podbielski and colleagues [5] reported that the azygos vein aneurysm presented an ideal circumstance for application of the video-assisted thoracoscopic technique. Although in our case the aneurysm was removed through a small thoracotomy, we also support resection of the azygos vein aneurysm with video-assisted thoracoscopic technique if it is necessary to remove it.
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References
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- Lena H., Desrues B., Heresbach H., et al. Azygos vein aneurysm: contribution of transesophageal echography. Ann Thorac Surg 1996;61:1253-1255.[Abstract/Free Full Text]
- Kurihara Y., Nakajima Y., Ishikawa T. Case report: saccular aneurysm of the azygos vein simulating a paratracheal tumor. Clin Radiol 1993;48:427-428.[Medline]
- Seebauer L., Prauer H.W., Gmeinwieser J., Sebening F. A mediastinal tumor simulated by a sacculated aneurysm of the azygos vein. Thorac Cardiovasc Surg 1989;37:112-114.[Medline]
- Mehta M., Towers M. Computed tomography appearance of idiopathic aneurysm of the azygos vein. Can Assoc Radiol J 1996;47:288-290.[Medline]
- Podbielski F.J., Sam A.D., II, Halldorsson A.O., Iasha-Sznajdar J., Vigneswaran W.T. Giant azygos vein varix. Ann Thorac Surg 1997;63:1167-1169.[Abstract/Free Full Text]
- Jain A., Blebea J.S. Post-traumatic pseudoaneurysm of the azygos vein in a patient with azygos continuation. J Compt Assist Tomogr 1994;18:647-648.[Medline]
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Abstract
Introduction
