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|Year : 2011 | Volume
| Issue : 1 | Page : 40-41
Isolated left innominate vein aneurysm: A rare cause of mediastinal widening
SG Dua1, AV Kulkarni2, NC Purandare1, S Kulkarni2
1 Bioimaging Unit, Tata Memorial Hospital, Parel, Mumbai, India
2 Department of Radiodiagnosis, Tata Memorial Hospital, Parel, Mumbai, India
|Date of Submission||13-Sep-2010|
|Date of Decision||16-Sep-2010|
|Date of Acceptance||04-Nov-2010|
|Date of Web Publication||31-Jan-2011|
A V Kulkarni
Department of Radiodiagnosis, Tata Memorial Hospital, Parel, Mumbai
Mediastinal widening in an adult is mostly nodal in origin. Occasionally vascular aneurysms may be the underlying cause, in which case the aorta or its branches are most frequently involved. Thoracic venous aneurysms, on the other hand, have been reported only in anecdotes, with fusiform aneurysm of the superior vena cava being the commonest. Isolated aneurysms involving the brachiocephalic/innominate vein are extremely rare. We describe detection of a saccular aneurysm of the innominate vein, as the underlying cause of mediastinal widening seen on a chest radiograph in a 42-year-old asymptomatic woman. The characteristic radiological findings of thoracic venous aneurysms are described with particular reference to the importance of multiplanar computed tomography in such settings. Also discussed is the role of imaging in the diagnosis and guiding the management of this rare entity.
Keywords: Innominate vein aneurysm, mediastinal widening, thoracic venous aneurysm
|How to cite this article:|
Dua S G, Kulkarni A V, Purandare N C, Kulkarni S. Isolated left innominate vein aneurysm: A rare cause of mediastinal widening. J Postgrad Med 2011;57:40-1
|How to cite this URL:|
Dua S G, Kulkarni A V, Purandare N C, Kulkarni S. Isolated left innominate vein aneurysm: A rare cause of mediastinal widening. J Postgrad Med [serial online] 2011 [cited 2014 Jul 23];57:40-1. Available from: http://www.jpgmonline.com/text.asp?2011/57/1/40/74286
| :: Introduction|| |
Aneurysmal dilatation of the thoracic veins is a very unusual cause of mediastinal widening. When present, fusiform dilatation of the superior vena cava is most commonly seen. Only a few case reports discuss isolated aneurysm of the innominate vein. We describe the incidental radiographic detection of a mediastinal mass in a 42-year-old woman. Further work up with computed tomography (CT) revealed an isolated saccular aneurysm of the left innominate vein as the underlying cause of the incidental finding.
| :: Case Report|| |
A 42-year-old woman was referred to our hospital for evaluation and further management of a mediastinal mass, which was incidentally detected on a pre-employment screening chest radiograph. She was normotensive and nonsmoker and was asymptomatic at presentation. There was no history of weight loss, night sweats, or fever. The occupational and family history was noncontributory. Chest radiograph revealed a soft tissue mass in the left hilar region [Figure 1], partially obscuring the left cardiac border. The silhouette of the descending aorta was visible through the mass. It had a convex lateral margin with the bifurcation of the pulmonary artery lying medial to it, suggesting an anterior mediastinal origin (hilum overlay sign).  She was advised a CT scan of the thorax for further characterization, followed by a guided biopsy to ascertain its etiology. Plain scan of the chest revealed a well-defined, 7-cm, rounded, homogeneously attenuating mass in the prevascular region. No intralesional calcification was noted. On contrast administration, the mass showed pooling of contrast and intense enhancement similar to that in the adjacent vein, and was seen in continuity with the left innominate vein [Figure 2]a. Coronal multiplanar reformatted image revealed saccular dilatation of the proximal left innominate vein [Figure 2]b, suggesting the diagnosis of a venous aneurysm. The distal left innominate vein, the right innominate vein, and the superior vena cava were normal. No extravasation of contrast material was noted. There were no filling defects to suggest thrombosis. Since the patient was asymptomatic, surgical treatment was deferred and she is being followed up.
|Figure 1: Frontal chest radiograph reveals mediastinal widening caused by a left hilar opacity with well-defined lateral convex margins. On careful inspection, it is noted that the bifurcation of the pulmonary artery lies medial to the lateral border of the opacity ("hilum overlay" sign) and the silhouette of the descending aorta is seen through it, localizing the opacity to the anterior mediastinum|
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|Figure 2: (a) Axial contrast enhanced CT image through the chest at the level of the aortic arch reveals intense contrast accumulation in the lesion, draining into the innominate vein. (b) Coronal maximum intensity projection multiplanar reformatted CT image reveals that the opacity in fact represented aneurysmal dilatation of the left innominate vein, thereby clinching the diagnosis|
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| :: Discussion|| |
Among adult patients, the commonest cause of anterior mediastinal widening is lymph nodal enlargement.  Not infrequently vascular aneurysms might be identified as the underlying cause of a widened mediastinal shadow. Arterial aneurysms, particularly those affecting the aorta, are more commonly seen, when compared to aneurysms of the thoracic veins which in turn are very rare. Only a few cases of thoracic venous aneurysms have been reported in literature,  with fusiform dilatation of the superior vena cava being the commonest. Isolated aneurysms involving the brachiocephalic vein are very rare and are reported in only 15 cases so far.  Most of the patients with thoracic venous aneurysms are asymptomatic and are diagnosed while investigating mediastinal widening discovered incidentally on chest radiographs and occasionally on cross-sectional imaging.  Symptoms, when present, are often due to complications which include compression of the surrounding structures, thromboembolism, and occasional rupture of the aneurysm, which in turn can be traumatic or spontaneous.  Little is known about the etiology and it is believed that venous aneurysms could be congenital or secondary to trauma, degenerative or inflammatory changes in the vessel wall,  or arteriovenous fistulae.  Anecdotal case reports have documented the association of cystic hygroma;  however no definite evidence of association has so far been provided.
On imaging, the typical roentgenographic appearance of thoracic venous aneurysms is mediastinal widening.  Pooling of contrast, intense homogeneous enhancement similar to the adjacent vessels and continuity with the thoracic veins are the cross-sectional imaging hallmarks of venous aneurysms. In recent years, use of multiplanar CT reformations to demonstrate the anatomic continuity of the aneurysms with the thoracic venous system has obviated the need for invasive venous angiography. Intravenous contrast also plays a vital role in the diagnosis of venous aneurysms, as seen in our case where a potential biopsy and consequent complications were averted after inspecting the contrast-enhanced series. The importance of intravenous contrast also lies in detecting or ruling out complications like rupture and thrombosis within the aneurysm. This information is vital in deciding treatment approach and planning surgical strategy if open-repair is indicated.
There are no suggested guidelines and the treatment is largely dictated by the clinical presentation and radiological characteristics. It is suggested that saccular aneursyms be subjected to surgical repair using cardiopulmonary bypass to treat or avoid imminent complications,  whereas uncomplicated asymptomatic aneurysms that remain stable in terms of size and do not show thrombosis can be safely observed. 
In summary, though thoracic venous aneurysms are rarely reported in literature, when encountered in clinical practice, this entity can be diagnosed on imaging alone. Communication between the radiologist and the clinician can thus preclude the need for further invasive diagnostic procedures and also guide further management as depicted.
| :: References|| |
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[Figure 1], [Figure 2]
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