FIND: There is an area of increased density in the lower part of the chest on the right. The rest of the image is normal.
IDENTIFY: The abnormal area is uniformly dense, about the same as the heart, apart from a branching low-density area medially (yellow arrow) which follows the line of the right main bronchus (blue arrow). This is an air bronchogram.
The abnormal area has a sharp upper margin which is almost horizontal (green arrow) .
The right border of the heart cannot be seen but the silhouette of the right side of the diaphragm (red arrows) remains visible.
LABEL: The air bronchogram means that there is airspace disease present. The lost right heart silhouette indicates that the airspace disease is next to the heart, therefore it is anterior, therefore the middle lobe is abnormal; the sharp upper border is caused by airspace disease contained in the lobe by the horizontal fissure; and the visible diaphragm silhouette means that there is at least some normal lung against the diaphragm (therefore in the base of the lower lobe).
MATCH: Airspace disease plus fever makes pneumonia the diagnosis, especially if the white cell count is raised.
SUMMARISE: Right middle lobe pneumonia.
You don't need a lateral view to make the diagnosis but it is useful to understand the appearances in the frontal view. The middle lobe forms the dense white triangle superimposed over the heart, and you can imagine the beam running along its sharp upper border (near the hilum) to give the line shown by the green arrow. Also along the top of the curve of the diaphragm, just behind the base of the triangle anteriorly, to give that silhouette.
Why is there so much disease in just one lobe? It may mean there is something blocking the airway so that bacteria can't be expelled easily and have more chance to grow. There could be thick mucus in a child, or possibly cancer in an older person.
At any age, enlarged lymph nodes (TB, other infections or cancer) could squeeze the airway. Sometimes the airway (especially to the middle lobe) is narrowed by scarring. However sometimes it just happens like this!
Because there may be a treatable underlying cause, this patient should have a follow-up examination in 6 weeks' time, and unless the X-ray looks much better, further investigation might be needed.