Mediastinal shift: Causes, Conditions and Method of Examination

Mediastinal Position

Position of mediastinum gives important clues to the nature of process in each hemithorax. Trachea is the index of upper mediastinum and heart of the lower mediastinum.

Method of Exam

Examine the position of mediastinum by standing in front of the patient. Make certain that the patient is seated straight or preferably standing erect. Trachea is the index of upper mediastinum. Heart is the index of lower mediastinum. Position of the heart can be used as an index of mediastinum only when it is not enlarged.

1. Inspect for the symmetry of clavicular insertion of both sternomastoids.
2. Tracheal Position: Gently bend the head to relax sternomastoids. Assess and compare the space between the trachea and sternomastoid on either side. Keep the tips of your index and ring fingers over the medial end of the clavicles. Then, with the middle finger, assess the space between the trachea and sternomastoid.
   Caution: Make sure that your nails are trimmed.
3. Position of Heart: Identify the location of apex of the heart by inspection and palpation.
   Caution: Make sure that the heart is not enlarged.

---

Normal
The right sternomastoid is slightly prominent normally. The trachea is slanted to the right. The apex of the heart is located on the 5th LIC space just internal to the midclavicular line.
Abnormal
Any deviation of the mediastinum is abnormal.
The mediastinum can be either pulled or pushed away from the lesion.

1. Pull: Loss of lung volume (Atelectasis, fibrosis, agenesis, surgical resection, pleural fibrosis)
2. Push: Space occupying lesions (pleural effusion, pneumothorax, large mass lesions)
3. Mediastinal masses and thyroid tumors
4. Kypho-scoliosis

Example:

Let us suppose that you have arrived at a decision that the mediastinum is shifted to left. It could be either due to a pushing lesion from right or a pulling lesion from left. The next step will help us identify which side is abnormal.
Caution :

1. Do not misinterpret apical impulse to mean deviated mediastinum in the presence of an enlarged Heart.
2. Difficult to interpret mediastinal position in a patient with Kypho-scoliosis.