The CXR shows a focal shadow in the right lower lobe with air bronchograms suggestive
of pneumonia. It is clearly in the right lower lobe because the right hemidiaphragm
is effaced. Right middle lobe shadows would efface the right heart border.
The presence of air bronchograms indicates pathology in the alveoli, as the conducting
airways remain patent with air. Water or blood can also occupy the alveoli
as a result of pulmonary edema or pulmonary hemorrhage respectively. There
should be other supporting signs such as cardiomegaly, upper lobe diversion, and
Kerley B lines with pulmonary edema. The differential diagnoses of a focal shadow
with air bronchograms include bronchoalveolar cell carcinoma and lymphoma. It
is important to follow-up the CXR to ensure that total resolution of infection
occurs. This may take up to three months in the elderly but generally some
improvement usually occurs within a week. The borders of the heart on a PA CXR
are shown in Fig. 1.2. SVC – superior vena cava, RA – right atrium, Ao – aortic
knuckle, LA – left atrium, LV – left ventricle