CXR

Question 1

What are the four hidden areas where consolidation is often missed on CXR

Answer 1

Apex, hilar region, retrocardiac and lung posterior to the diaphragm

Question 2

Discuss what forms normal lungs markings

Answer 2

Normal lung marking are made soley from normal vessels and nothing else. There is complete lack of mraking in the costophrenic angle as the vessels here are too small to be seen

If there are marking here then interstitial disease or oedema is likley

Question 3

Discuss aspects of a normal lateral x-ray

Answer 3

1) the vertebral bodies gradually appear blacker as you look from t3-12 “ grey at the top and black at the bottom”
2) both domes of the diaphragm should be visible. The anterior aspect of the left lobe will normally be obscured by the heart positioned over this part of the dome
3) there is no abrupt change in density over the cardiac shadow

Question 4

Discuss the structures that make up the hila on a frontal chest x-ray

Answer 4

The hilum is the site at which the bronchi and vessels enter or leave the lung

The two hila are approximately the same size and of very similar density

Question 5

Discuss analysis of the frontal x-ray

Answer 5

1) check whether the CXR is a PA or an AP radiograph and whether it was obtained erect or supine
2) Check whethere there is an adequate inspiration
3) direct anaylsis towards you primary clinical conern

4) Systemic anaylysis of the rest of the x-ray 
a- airway + hilum 
b- bones 
c: cardiac silhouette
d: diaphragms 
e: edges chostophrenic and cardio phrenic 
f: fields 
g: gastric bubble 
H: hilum 
I: indwelling lines or devices

Question 6

Discuss analysis of the lateral chest x-ray

Answer 6

1) are the vertebral bodies becoming blacker form above downwards (if not ie they are becoming whiter or greyer suspect disease in lower lobe or in pleural sapce)

2) are the domes of the diaphragm clearly visualised
- The left dome physiologically disappears anteriorly becuase the heart is tight up against it

3) is there an abrupt change in the density across the heart shadow
4) correlate finding with frontal CXR

Question 7

Discuss evaluation of subtle pneumonias

Answer 7

Search for any evidence of a silhouette sign ( an intrathoracic lesion or density touching a border of the heart, aorta or diaphragm will obliterate part of the border on the CXR

Assess the mediastinal and diaphragmatic boundaries and borders

Question 8

Discuss pathphysiology of the silhouette sign

Answer 8

The borders of the heart and both domes of the diaphragm are visibale on a normla CXR becuase the air in the lung contrasts with the water density of the heart and diaphragm. If the lung air is replaced by pus or other fluid the immediatley adjacent border will disappear or be ill defined.

Question 9

Discuss supine CXR evaluation of pneumothorax in a trauma patient

Answer 9

On a supine CXR the pleural air will rise to the highest point in the pleural space - ie the anterior aspect of the thorax – consequently the lung base and the area around the heart need careful evaluation

Question 10

Discuss signs of heart failure on CXR q

Answer 10

1) increased cardiac shadow - almost all patient with LVF have an enlarged heart - theoccasional exception is a patient with an acute MI

Early signs

• oedema: poorly defined margins of the hilar vessels
• oedema septal lines (kerley b lines)
• small pleural effusion usually bilaterall
• upper lobe pulmonary venous diversion

Later signs

• intersitial shadowing
• –peribronchial cuffing and perihilar haze
• alveolar shardowing ( typically in batwing distribution)
• larger pleural effusions usually bilateral