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2011-06-09-08 Evaluation of the upper mediastinum using a four level approach © Quiroga www.TheFetus.net

Evaluation of the upper mediastinum using a four level approach 
Hector Quiroga, MD.

Centro Médico Profesional Rosancar. Barquisimeto, Estado Lara, Venezuela.


Introduction

The fetal upper mediastinum can be evaluated using a four level approach. Each level has a well define landmarks that can be  recognized easily. 

1)  Level I or lower level

This is the lower level of the fetal upper mediastinum, and can be recognized by identifying the division of the main pulmonary artery into the right and left branch. 
This level is useful to identify cases of pulmonary stenosis or absent pulmonary valve.  

Images 1,2: Level 1 of the fetal upper mediastinum, main pulmonary artery (MPA), left pulmonary artery (LPA), right pulmonary artery (RPA), ascending aorta (Ao) and superior vena cava (SVC).

 

2) Level II or Mid-lower level 

Is recognized by the identification of the left and right pulmonary bronchi and the ductus arteriosus joining the descending aorta.
This level is useful for evaluation of the ductus arteriosus, we can obtain the velocity wave flows of the ductus.

Images 3,4: Right and left bronchi (green dots), ductus arteriosus, aorta (Ao) and superior vena cava (SVC).

 

3) Level III or mid apical level

The main feature is the identification of the carina, cartilaginous ridge within the trachea, which is an anechoic structure located in front of the spine and by the “V” shape formed by the ductus arteriosus and the aortic arch.
Level III is important for evaluating anomalies or the aortic arch, vascular rings, and persistence of the left superior cava.

Images 5,6: Images show the carina (green dot), superior vena cava (SVC), aortic arch (AoA). Note the “V” shape formed by the ductus arteriosus and the aortic arch.

 

4) Level IV or apical level

We identify the left brachiocephalic vein (innominate vein) joining the right brachiocephalic vein. The trachea can be detected in front of the spine.
We can evaluate thymus and the drainage of the azygos vein in to the left superior cava.

Images 7,8: Image shows trachea (green dot), and the left brachiocephalic vein (innominate vein) joining the right brachiocephalic vein.

 
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