Idiopathic azygos vein aneurysm: a rare cause of mediastinal mass

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  1. Miguel Gallegoa,
  2. Rosa M Mirapeixc,
  3. Eva Castañerb,
  4. Ch Domingoa,
  5. Josep G Matab,
  6. Albert Marína
  1. aPulmonary Department, bRadiological Department, cConsorci Hospitalari del Parc Taulí, 08208 Sabadell, Barcelona, Spain Department of Beefcake, Autonomous Academy of Barcelona, Bellaterra, Barcelona, Espana
  1. Dr M Gallego.

Abstruse

Venous aneurysm of the azygos arch is a very rare cause of mediastinal mass and is usually an incidental finding on chest radiography. Nowadays the diagnosis is fabricated past non-invasive tests such as thoracic CT scanning and/or magnetic resonance imaging. The example is described of an asymptomatic woman in whom a mediastinal mass due to an azygos vein aneurysm was diagnosed by non-invasive procedures, the aetiology of which, in all probability, was idiopathic.

  • mediastinal mass
  • azygos vein
  • aneurysm

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  • mediastinal mass
  • azygos vein
  • aneurysm

Enlargement of the azygos arch vein tin can be due to an increase in central venous pressure, portal vein hypertension, azygos continuation of the inferior vena cava (IVC), a neoplasm, or local thrombosis located in the inferior vena cava.ane ,2 High central venous force per unit area is past far the virtually mutual crusade and mainly results from cardiac decompensation.iii Truthful aneurysmal dilatation is a highly uncommon entity which has been reported on very few occasions.one ,ii ,iv-9

Nosotros report a instance of azygos vein aneurysm diagnosed by computed tomographic (CT) scanning and magnetic resonance imaging (MRI).

Instance written report

A not-smoking 64 year old woman was referred to our hospital with coughing, wheezing, and scanty expectoration. Except for mild hypertension, her past medical history was unremarkable. No significant trauma was recorded. Physical examination was normal except for the presence of bilateral wheezing; no signs of cardiac failure were detected. Blood analysis (including a haemogram, differential prison cell count, hepatic and renal function, ionogram, and proteinogram) and arterial claret gas tensions in room air were normal.

The posteroanterior chest radiograph was normal (fig 1a) only the lateral view showed a possible retrotracheal mediastinal mass (fig 2). A 2nd breast radiograph on expiration showed a mediastinal mass (fig1b). A CT browse before and after intravenous dissimilarity enhancement confirmed the presence of a slowly enhancing mass in the pathway of the azygos arch measuring three.5 cm (fig 3). Axial T1 weighted and T2 weighted magnetic resonance imaging showed a heterogeneous mass and, later on injection of gadolinium-DTPA, the lesion became homogeneously hyperintense and isointense with respect to the rest of the vascular structures (aorta, vena cava). However, contrast uptake occurred later due to upward venous catamenia in the azygos vein (fig iv). The findings were compatible with an aneurysm of the azygos vein.

Discussion

Well-nigh patients with venous aneurysms are asymptomatic and the lesion is detected as an incidental finding on the chest radiograph (table 1). The aetiology of the azygos aneurysm was unknown, but since no history of high pressure level in the azygos system or contempo trauma were recorded despite extensive anamnesis, clinical and radiographic examination, it was assumed to be congenital.

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Table 1

Characteristics of venous aneurysms reported in the literature

During the 3rd and fourth weeks of gestation the fundamental vein organization develops. This organisation consists of paired anterior and posterior fundamental veins which unite to form a short mutual central vein. The anterior cardinal vein gives rise to the subclavian, the internal jugular, the brachiocephalic vein, and the superior vena cava. The posterior key veins are replaced by two additional pairs of veins, the subcardinal and the supracardinal veins (which gives rise to a portion of the junior vena cava and the azygos system). A segment of the correct supracardinal vein anastomoses with a function of the superior vena cava (derived from the anterior cardinal vein) so that the azygos drains into the right atrium via the superior vena cava.ten ,11 It has been postulated that an aplasia or hypoplasia of the superior vena cava could affect azygos drainage,half dozen but in our example no cava affection was observed. Moreover, the aneurysm was localised at the junction of the supracardinal and the anterior cardinal veins which, anatomically, is a weak point. This lends support to the idea of a congenital aetiology in our instance.

Veins are composed of 3 layers: the intima, the media, and the adventitia. During vasculogenesis the first layer to announced is the intima, and the tunica media develops one time a stable vascular pattern has been formed (past interaction of the epithelium and the mesenchyma). In cases of congenital dilatation the venous layer to be afflicted is the media, as opposed to acquired dilatation (i.e. varicose veins) where there is a fibrosis beneath the endothelium.12 To confirm this hypothesis it is necessary for a histological study to be performed to detect alterations in the venous endothelium.

In patients with an azygos venous aneurysm a frontal chest radiograph may demonstrate a prominent azygos vein or an aberrant mediastinal density. On a frontal chest radiograph, characteristically, the size of the aneurysm changes with the respiratory movements (specially with Valsalva manoeuvre), as happened in our case.1 In the past, venography used to be performed to advise the diagnosis.two ,6 Nowadays, dynamic enhanced CT scanning and MRI not only provide non-invasive methods for the evaluation of vascular abnormalities,5 ,13 but tin besides rule out other entities which may produce enlargement of the azygos vein. However, the blood flow in the aneurysmal vein is sometimes so slow that MRI may provide an prototype similar to a solid mass.5 The signal

intensity of the lesion, in our case, varied depending on whether upflow or downflow were saturated, thus confirming its vascular nature.

Although this entity is very rare, we believe that it should exist borne in mind for the differential diagnosis of a mediastinal mass. Moreover, it should be stressed that, for an authentic diagnosis, invasive tests are not necessary. Follow up of this lesion is important as an azygos vein aneurysm may grow.2

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