Anatomy clinical correlates: Mediastinum

We all know how important the heart is, but everyone forgets about the mediastinum, which is the area between the two lungs where the heart actually sits!

The mediastinum doesn't just house the heart, but many important structures in the thoracic cavity from the superior thoracic aperture down to the diaphragm.

So let's take a closer look at the clinical conditions that can affect the mediastinum and the structures within it.

First up, there is widening of the mediastinum, which can be seen on a chest x-ray.

Since the mediastinum contains so many structures, each of them can contribute to pathological widening.

It can be observed after a trauma that causes laceration or dissection of the great-vessels, typically the aorta, which can cause hemorrhaging into the mediastinum.

Other times, malignant tumors such as lymphomas can produce massive enlargement of mediastinal lymph nodes and widening of the mediastinum.

Another cause of mediastinal widening is heart hypertrophy due to congestive heart failure.

Now, next up, there’s the esophagus.

The esophagus may have up to four normal anatomic constrictions as it descends, however there are three sites of constriction that can occur specifically in the posterior mediastinum caused by three structures it meets on its way down: two thoracic constrictions with the first being where the esophagus is crossed by the arch of the aorta, and second where it is crossed by the left main bronchus, and one diaphragmatic constriction where it passes through the esophageal hiatus of the diaphragm.

The fourth site of constriction occurs in the cervical region before the esophagus enters the mediastinum, where constriction may be caused by the cricopharyngeus muscle.

At these locations, there’s a slower passage of substances and is where foreign objects that are swallowed are most likely to lodge.

These narrowings can be seen in chest radiographs of a person who underwent a barium swallow study.

These areas are also at risk of stricture after ingesting caustic liquids such as cleaning products.

Don’t try this at home!!

Now, even though we try to prevent foreign objects going into our esophagus, one thing we are okay with is the use of transesophageal echocardiography, or TEE for short.