Chest radiograph (A) shows near complete white-out of right hemithorax causing mediastinal shift and leftward tracheal deviation.Sagittal CT images (B and C) show a huge approximately 16 x 16 x 12 cm mediastinal mass occupying the entire right hemithorax with mass effect, encasing all major vessels leading to severe compression of superior vena cava and bilateral brachiocephalic veins
. There is also compression of the right main stem bronchus with complete right lung collapse.
Regarding the right subclavian vein catheterization, the venous anatomy should be taken into consideration, as there are two angles in the catheter route: the subclavian to internal jugular junction and the contribution of two brachiocephalic veins
to form the superior vena cava.
The hemiazygos system (HV and AHV), together with the left superior intercostal vein, drains the lower eight left posterior intercostal and upper four left posterior intercostal veins (LPIVs) into the azygos and left brachiocephalic veins
, respectively (Dahran & Soames, 2015).
Although USG Doppler was helpful in diagnosis of our patient, it has limited capabilities in visualizing central subclavian and brachiocephalic veins
. Contrast venography can confirm the diagnosis of SVC syndrome, but venous cannulation may be difficult in setting of obstruction apart from other contrast related complications.
Other signs that suggest mediastinal air on the CXR include the 'continuous diaphragm sign' (air trapped posterior to the pericardium), 'Naclerio's V sign', which is formed by the junction of mediastinal air in the left lower mediastinum and extrapleural air adjacent to the left hemidiaphragm, the 'V sign' that is formed by the confluence of the superior margins of the brachiocephalic veins
, the 'ring around artery sign' that results from air outlining the pulmonary artery and the main branches, the 'double bronchial wall sign' formed by air outlining the bronchi, air in the pulmonary ligament and irregular bilateral apical extrapleural air.
(8,9) This may be due to anatomic differences, namely the larger right jugular bulbs, shorter right brachiocephalic veins
, lack of valves in the right brachiocephalic veins
, and a higher incidence of incompetent left subclavian venous valves.
Right and left superior intercostal veins have been traced to their points of termination into the right and left brachiocephalic veins
, correspondingly the hemiazygos and the accessory hemiazygos are traced on the left side of the bodies of the thoracic vertebrae behind the descending thoracic aorta.
[8-15] Placement of catheter tips above or near the cephalad origin of the SVC with the infusion of hypertonic or irritative solutions risks thrombosis from endothelial damage, embolism, and stenosis of the brachiocephalic veins
or catheter erosion into the mediastinum leading to hydrothorax or hydro-mediastinum.
The most important vessels found in this region are the internal and external jugular veins, axillary vein, costocervical, deep cervical, vertebral, left brachiocephalic veins
and the cranial vena cava, in addition to the left common carotid, axillary, costocervical trunk, dorsal scapular, deep cervical and superficial cervical arteries (POPESKO, 1997).