How to interpret a Chest Xray?

The way you should interpret the chest X-ray is either from outer to inwards or inwards to outwards.

This is a Normal Chest X-ray.  The way you should interpret the chest X-ray is either from outer to inwards or inwards to outwards. I prefer inwards to outwards. 

Look at the following things in the image provided-

  1. Trachea and both main bronchi - It should be central and we will also be able to trace both main bronchi
  2. Pulmonary hilum- The pulmonary hilum in a radiograph is an angle formed from the joining of the descending pulmonary artery with the pulmonary veins. There are three rules of pulmonary hilum-  It should be concave outwards. The left hilum is higher than the right side.
  3. Lung parenchyma-  Look at the lung parenchyma by comparing the two sides from up to down ( cranial to caudal ).  Compare the right upper with left upper lung, right middle with left middle and right lower with left lower lung. Look at the bronchovascular markings in the chest. The bronchovascular markings should have a gravitational distribution, which means that the lower lobe vessels should be larger than the upper lungs. Also, because their size decreases progressively as they go peripheral, you shouldn’t be able to see the vessels in the peripheral third of the lungs.  When you see a pathology (nodule/mass in the lung), you should note the location of the lesion and mention it in zones. The zones of the lungs are described based on looking at the lower margins of the anterior ribs, and classified as follows-
  • From the apex of lung to lower border of 2nd anterior rib- Upper zone. 
  • From the lower border of 2nd anterior rib to lower border of 4th anterior rib- Middle zone.
  • From the lower border of the 4th anterior rib to lower border of 6th anterior rib- Lower zone.

1. Look at the hidden areas of the lungs. The hidden areas of lungs are areas that are not well visualized when the chest X-ray is read fast, from a distance. Pathology in the hidden areas is commonly missed even by good radiologists. The hidden areas of the lung are the apices ( the part of the lung above the clavicles), behind the ribs, below the diaphragms and behind the heart (retrocardiac area).

2. Calculate the cardiothoracic ratio- The cardiothoracic ratio is calculated as follows-

Cardiomegaly is diagnosed when the size of the heart is more than ½ of the thoracic diameter. It is measured as follows-

  • A vertical line is made joining the spinous processes.
  • The maximal distance from the vertical line to the right heart border is given as ‘ A’.
  • The maximal distance from the vertical line to the left heart border is given as ‘ B’.
  • The size of the heart is estimated as A+B.
  • The maximal thoracic diameter is given as ‘C’.
  • Cardiomegaly is given as A+B/ C if more than 50% in adults and 60% in children.

3. Look at the costo-phrenic angles- The costo-phrenic angles should be acute ( less than 90 degrees). 

4. Look at the ribs and the vertebra. The ribs should be counted and looked at one by one, so as not to miss fractures/ bony lesions.

5. Look at the soft tissues.

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