Fig. 27.—Unresolved pneumonia with peribronchial formation of fibrous tissue; bronchiectasis. Autopsy 487.
Fig. 28.—Unresolved pneumonia with bronchiectasis showing new formation of fibrous tissue about a greatly dilated bronchus of which the epithelial lining has been lost. Autopsy 487.
Thickening, cellular infiltration and fibrosis of the bronchial walls with interstitial inflammation and fibrosis of immediately adjacent alveolar septa are found about the ramifications of the bronchial tree and may be followed to the smallest bronchi. When the respiratory bronchioles are reached it will be found that the alveoli which stud their walls are implicated in the change. The fibrin which they contain is infiltrated with lymphoid and plasma cells, and with progress of the lesion is invaded by fibroblasts and capillaries. Infiltration and fibroid thickening extends from the bronchiolar wall to the alveolar septa continuous with it (Fig. 31 with measles). Similar changes occur about the alveolar ducts, and about the orifices of the tributary infundibula (Fig. 32), peribronchiolar foci of acute inflammation having assumed the characters of a chronic inflammatory process. Fibrin within the alveoli contains round cells and fibroblasts. With thickening of alveolar walls the alveolar lumina may be much diminished in size and often persist as spaces lined by cubical cells. Polynuclear leucocytes are usually numerous within the alveolar duct and in a few alveoli immediately adjacent to it, but elsewhere throughout the focus of inflammation round cells are predominant. The changes which have been described correspond with the transformation of ill-defined, gray or reddish gray spots of consolidation grouped about the terminal bronchi into firm sharply defined grayish white nodules having the consistence and appearance of miliary tubercles.
One of the most constant characters of pneumonia following influenza is its hemorrhagic character. In the earlier stages of pneumonia phagocytosis of red blood corpuscles by large mononuclear cells is frequently seen. In association with the chronic changes which have been described, large mononuclear cells filled with brown pigment, doubtless formed from red corpuscles, are often found within the alveoli. These pigment containing cells are similar to those commonly associated with chronic passive congestion of the lungs.
In one instance (Autopsy 457) hemorrhagic peribronchiolar pneumonia has been found in process of organization. The bronchioles and alveoli adjacent to them contain polynuclear leucocytes, but intervening alveoli almost uniformly contain blood and are the site of new formation of connective tissue. Interalveolar septa are thickened and alveoli which are lined by cubical epithelium are often diminished in size. In many places fibroblasts have penetrated in considerable number into the blood within the alveoli and occasionally newly formed capillaries are found within them.
Lobular patches of pneumonia are often found in process of organization (Autopsies 370, 421, 423, 433, 463, 472 and 473). Microscopic examination shows that whole lobules well defined by thickened septa are the site of chronic interalveolar inflammation and intraalveolar organization of exudate, whereas adjacent lobules are air containing and relatively normal. In the earlier stages of the process fibrin present within the alveoli is invaded by fibroblasts, mononuclear wandering cells and blood vessels but in the later stages fibrin has disappeared; the lumina of the alveoli are occupied by cellular fibrous tissue and in places the thickened alveolar walls and intraalveolar fibrous tissue have been fused to form wide patches of new tissue.
With chronic bronchopneumonia confluent lobular consolidation occasionally has a gray ground upon which are scattered small yellow spots clustered about the small bronchi (Autopsies 421, 423 and 431). Microscopic examination has shown that the yellowish spots correspond to dilated bronchioles filled with purulent exudate and surrounded with alveoli containing many polynuclear leucocytes. In the interstitial tissue about the bronchiole and between adjacent alveoli plasma cells are often present in great number. Between these spots of subacute bronchiolar inflammation lung tissue is the site of interalveolar proliferation of fibrous tissue and intraalveolar organization of exudate.
In all instances of chronic bronchopneumonia there has been peribronchial pneumonia in a zone encircling small bronchi with no cartilage and the smallest of the bronchi which have cartilage in their wall; thickening of interalveolar septa, organization of peribronchial fibrinous pneumonia and partial disappearance of alveoli have been described. In the following autopsy peribronchial fibroid pneumonia has been so advanced that conspicuous patches of gray white tissue surrounding bronchi have replaced in some parts of the lung a considerable part of the lung substance.