The analogy of the gate and field are relevant to this X-ray, however the reference in this picture should be explained; it is a personal joke. One of my senior colleagues objected to the use of the term Lung fields when used in radiology reports. It was her personal bete noir and she would sharply reprove any junior staff foolish enough to use the phrase, “Cows live in fields! Where are the lung cows?” she would say.
The index X-ray was from a child with lobar pneumonia (in the right upper lobe) with a white-out in the right upper lung field. The pneumococcus is the commonest organism causing this disease. As students we were required to learn the pathological phases of pneumonia; Congestion, Red hepatisation, Grey hepatisation and Resolution, through which the disease passes. There are numerous defences designed to protect to the healthy lung, which is usually sterile with no resident bacteria: Nostril hairs stop large particles, epiglottis prevents incursion of food particles, respiratory mucus traps inhaled bacteria, and cilia – microscopic hair-like structures – waft debris out of the airways. Immune mechanisms including white cells protect and ingest bacteria. When these gates are inadequate or overwhelmed by sheer numbers of bacteria then an infection occurs.