MEDIASTINUM AND HILUM IN CHEST XRAY

1. CHEST X-RAY
MEDIASTINUM AND HILUM

2. Normal mediastinal contours
If one of these contours is obscured, then an abnormality is likely to be located
next to the structure that the contour represents

3. Anterior mediastinal mass - Thymoma
•The mediastinal contours are bulging due to a large mass – in this case a thymoma
•It is possible to determine that this mass is located anteriorly in the mediastinum
•The aortic knuckle (mid mediastinum) and both the azygo-oesophageal and
descending aorta lines (posterior mediastinum) are clearly visible and so the mass
cannot be located adjacent to these structures

4. Anterior mediastinal mass - Thyroid
•A large soft tissue mass causes narrowing of the trachea and deviates it
towards the left side
•The right paratracheal stripe is obscured at the level of the mass but remains
visible below the mass
•This patient had an enlarged thyroid gland (goitre) which was visible clinically
and was shown to be benign on imaging with ultrasound

5. Superior mediastinal mass - Lymphoma
•A soft tissue mass widens the superior mediastinum
•The mass blends in with the upper edge of the aortic knuckle and obscures
the right paratracheal stripe
•This mass was found to be lymphoma following lymph node biopsy
•Bilateral effusions are also present

6. Posterior mediastinal mass
•A large round area of increased density indicates the presence of a soft tissue
mass in the region of the left hilum
•Left heart border (adjacent to the anterior mediastinum) remains well defined
•Vessels of the left hilum area – including the left pulmonary artery (middle
mediastinum) – also remain well defined
•Obscuration of the descending aorta (posterior mediastinum) confirms the mass
is located posteriorly

7. Unilateral hilar enlargement - Lung cancer
•In this image the left hilum is too big and too dense (white) and the normal
pulmonary vessels are difficult to delineate
•Following bronchoscopy and tissue biopsy this mass was found to be a primary
bronchogenic cancer

8. Bilateral hilar enlargement - Sarcoidosis
•In this image both the hila are enlarged and of increased density
•Bilateral hilar enlargement is the classic chest X-ray appearance of sarcoidosis
– as was found to be the case in this patient following lymph node biopsy

9. Bilateral hilar enlargement -
Lymphoma
•Bilateral hilar enlargement is not always sarcoidosis
•Lymph node biopsy showed this to be lymphoma rather than sarcoidosis

10. Radiation fibrosis
•This patient had been treated with radiotherapy for Hodgkin’s disease several years
previously
•The lungs adjacent to the hila are scarred and appear of increased density
(highlighted areas)
•Radiation fibrosis should not be diagnosed without a history of previous
radiotherapy
•Distribution of lung scarring depends on the specific site irradiated

11. Aneurysmal descending aorta
•This image shows a grossly enlarged descending aorta due to a thoracic aortic
aneurysm

12. Aneurysmal ascending aorta
•This patient had aortic stenosis due to a congenital bicuspid aortic valve
•The ascending aorta is enlarged due to post-stenotic dilatation – a common
phenomenon in patients with aortic stenosis
•Patients with aortic stenosis may have a normal chest X-ray
•Patients may also have cardiomegaly indicating left ventricular failure – not yet
developed in this patient

13. Aortic unfolding
•Unfolding’ of the aorta – a common X-ray finding in elderly patients – is a
phenomenon which arises due to elongation of the ascending aorta with age
•It is not usually considered a pathological finding in itself and should not be
mistaken for an aortic aneurysm
•It is often associated with calcification of the aorta – as in this image – which is
a sign of atherosclerosis

14. Coarctation of the aorta
•Features of coarctation of the aorta may be visible on a chest X-ray
•Coarctation causes blood flow to be deviated from the upper part of the
descending aorta into the intercostal vessels of the 4-8th ribs bilaterally which
results in ‘notching’ of their inferior edge

15. Coarctation - figure 3 sign
•The narrowing (coarctation) results in the descending aorta taking on a
contour said to resemble a figure ‘3’

16. Coarctation - Stent
•(Same patient as two images above)
•This patient has been treated with stent insertion at the point of coarctation

17. Hiatus hernia – Large
•Herniation of the stomach above the diaphragm (hiatus hernia) is a common
finding on a chest X-ray
•Hiatus hernias may be very large – as in this image
•Seeing a gas/fluid level helps to make the diagnosis

18. Hiatus hernia – Small
•Here is a smaller hernia
•The gas/fluid level is less distinct
•Note: Hiatus hernia may not be visible on a chest X-ray

19. Pneumomediastinum
• May result from injury to the lungs or structures of the mediastinum such as the
airways or oesophagus
•The mediastinal pleura is separated from the mediastinum and becomes visible
as a thin white line
•This can be a very subtle finding and may be associated with other features of
tracking gas such as surgical emphysema or pneumothorax