In association with this lesion there are almost invariably severe lesions of the bronchi. Purulent bronchitis was noted in 47 of the 61 instances, in which this nodular bronchopneumonia was found at autopsy. An index of the severity of the bronchial injury is the frequency with which bronchiectasis has occurred; dilatation of small bronchi was observed in 24 instances. In 10 instances the bronchi were encircled by conspicuous zones of hemorrhage.
In association with this peribronchiolar lesion the lung is often voluminous and fails to collapse on removal from the chest. Pressure upon the lung squeezes from the smallest bronchi, both in the neighborhood of the nodular consolidation and elsewhere, a droplet of viscid, semifluid mucopurulent material. The presence of this tenacious material throughout the small bronchi doubtless explains the failure of the lung tissue to collapse. Interstitial emphysema has been present in some of these lungs.
A red zone of hemorrhage has occasionally been observed about the foci of peribronchiolar pneumonia. A further stage in the same process is represented by hemorrhage into all of the alveoli separating these patches of consolidation. This hemorrhagic lesion, which will be described in more detail later, has been found repeatedly in the same lung with peribronchiolar pneumonia, being present in 8 among the 61 autopsies cited. Lobular bronchopneumonia accompanied the peribronchiolar lesion 27 times and lobar pneumonia accompanied it 20 times.
When an abscess caused by hemolytic streptococcus is associated with peribronchiolar pneumonia, empyema is present, but otherwise pleurisy is absent or limited to a scant fibrinous exudate.
Fig. 3.—Acute bronchopneumonia with peribronchiolar consolidation; a respiratory bronchiole partially lined by columnar epithelium passes into alveolar duct and the adjacent alveoli are filled by polynuclear leucocytes. Autopsy 333.
Histologic examination demonstrates very clearly the relation of this lesion to the bronchioles (Fig. 3). These passages are filled and distended with an inflammatory exudate consisting almost entirely of polynuclear leucocytes. The respiratory bronchioles are beset with alveoli often limited to one side of the tubule and these alveoli are filled with leucocytes. The alveolar ducts, distinguishable from the bronchioles by the absence of columnar or cubical epithelium and by possession of smooth muscle, are similarly filled with leucocytes; the numerous alveoli which form the walls of the alveolar ducts are distended by an inflammatory exudate. In sections which pass through an alveolar duct and one or more of its infundibula, the further extension of the lesion may be determined (Fig. 4). The infundibulum in proximity with the alveolar duct contains polynuclear leucocytes and the same cells are seen in the alveoli which here form its wall, but the intensity of the inflammatory reaction diminishes toward the periphery, so that the distal part of the infundibulum, which is much distended and in consequence more readily definable than usual, is free from inflammatory exudate.
Fig. 4.—Acute bronchopneumonia with peribronchiolar consolidation; a respiratory bronchiole is in continuity with an alveolar duct and two distended infundibula; alveoli about bronchiole, alveolar duct and proximal part of infundibula contain polynuclear leucocytes, the distal part of the infundibula showing no evidence of inflammation. Autopsy 333.
Occasionally there is irregularly distributed hemorrhage and perhaps some edema in the alveoli immediately adjacent to those which form the peribronchiolar focus of inflammation. In such instances small bronchi, that is, air passages, lined by columnar epithelium and devoid of tributary alveoli, may be surrounded by a zone of hemorrhage; immediately surrounding the bronchus, the wall of which shows intense inflammation, alveoli, in a zone of which the radius represents several alveoli, are filled with blood. This hemorrhagic zone is continued from the bronchus over the focus of inflammation which surrounds the bronchiole.