This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Catarrhal Pneumonia Or Bronchopneumonia is an inflammatory condition of localized areas of the lung resulting from inflammation of the terminal bronchioles, capillary bronchitis. Is also known as lobular pneumonia, on account of involving lobules of the lung. Occurs generally in young children and old people. It is due in the majority of cases to infection, and is most common as a sequel to the infectious fevers that are accompanied by bronchitis, as in measles, whooping-cough, and influenza. The diplococcus of Fränkel is the most common 23 organism but is usually associated with other bacteria. It also follows the inspiration of particles of septic matter, aspiration pneumonia. If there has been hypostatic congestion to predispose, hypostatic pneumonia may arise from the entrance of infectious particles.
In bronchopneumonia both lungs are generally diffusely involved, areas of consolidation being scattered throughout. In the non-pigmented lungs of children these areas are quite conspicuous. On the pleural surface small nodular elevations, dark red or slightly reddish-gray in color, are seen. Are smooth on section, and are usually surrounded by a narrow zone of congestion. These areas are firm, and when separated from the surrounding tissue will sink in water. The lung in the immediate vicinity may be emphysematous, other portions being collapsed - atelectasis. Microscopically the alveoli are found to contain an exudate, albuminous in character, in which desquamated epithelial cells, leukocytes, and erythrocytes are present. It is seldom that much fibrin is found. There is also a marked round-cell infiltration of the septa. The red blood-cells and the leukocytes are not, as a rule, found in large numbers unless the infection has been due to pyogenic organisms. The exudate may then be hemorrhagic or purulent; in either case gangrene may develop.
The small bronchi are usually inflamed and filled with an exudate similar to that in the air vesicles.
The lung returns to its normal condition through fatty degeneration of the exudate with absorption and expectoration.