Geographic changes in the lungs refer to areas of abnormal lung parenchyma with sharply demarcated borders or regions that exhibit different attenuation or density from the surrounding lung tissue. This term is often used to describe patterns of lung disease that have a distinct, map-like distribution, as if outlining an anatomical or pathologic “territory.”

Geographic changes may indicate processes such as:

Consolidation or ground-glass opacities due to infection, inflammation, or hemorrhage.
Fibrosis or other chronic lung changes that respect anatomic boundaries like lobes or segments.
Mosaic attenuation patterns seen in small airway diseases or vascular disorders, reflecting differences in ventilation or perfusion.
Emphysematous changes or cysts distributed in a well-defined manner.
The use of “geographic” implies that the borders and distribution of the abnormality are visually distinct, often aiding in narrowing down differential diagnoses based on the pattern of involvement.