The document discusses the shift of the mediastinum seen on chest x-rays. There are 6 figures showing examples of conditions that can cause the mediastinum to shift including a collapsed left lung, pneumonectomy, peanut in the right mainstem bronchus, large unilateral pleural effusion, tension pneumothorax, and congenital diaphragmatic hernia. The shift of the mediastinum occurs when the volume of one lung is reduced, such as from collapse, fluid, or herniated bowel occupying the chest cavity, causing pressure on mediastinal structures and shifting them to the opposite side.

1. 31 Shift of the Mediastinum*

2. CLINICAL IMAGAGING
AN ATLAS OF DIFFERENTIAL DAIGNOSIS
EISENBERG
DR. Muhammad Bin Zulfiqar
PGR-FCPS III SIMS/SHL

3. • Fig C 31-1 Collapse of the left lung. (A) Initial
examination showing old healed granulomatous
disease. Note the position of the left infrahilar
nodes (arrow). (B) Repeat chest film 2 days later
shows opacification of the entire left hemithorax
due to a mucus plug and a shift of the
mediastinum to the affected side. Note the
change in position of the left infrahilar
calcifications (arrow).

4. • Fig C 31-2 Pneumonectomy. Opacification of
the left hemithorax with multiple surgical
clips. The trachea and other mediastinal
contents are shifted to the affected side.

5. • Fig C 31-3 Peanut in the right main-stem
bronchus. (A) During inspiration, the lungs of this
2-year-old boy are well aerated. Air trapping in
the right lung is seen during expiration (B) and
with the right side down (C). The normal left lung
is underaerated when that side is down (D).61

6. • Fig C 31-4 Large unilateral pleural effusion.
The left hemithorax is virtually opaque, and
there is shift of the mediastinum to the right.

7. • Fig C 31-5 Tension pneumothorax. The left hemithorax
is completely radiolucent and lacks vascular markings.
There is a dramatic shift of the heart and mediastinum
to the right. The left hemidiaphragm is markedly
depressed, and there is spreading of the left ribs.

8. • Fig C 31-6 Congenital diaphragmatic hernia.
Multiple lucencies in the left chest due to gas-
filled loops of bowel. The heart and
mediastinal structures are shifted to the right.

9. • Fig C 31-6 Congenital diaphragmatic hernia.
Multiple lucencies in the left chest due to gas-
filled loops of bowel. The heart and
mediastinal structures are shifted to the right.