Microscopic examination shows that the epithelium of dilated bronchi has disappeared and the denuded surface is covered by fibrin and polynuclear leucocytes; fissures extend from the lumen through the bronchial wall into the surrounding alveolar tissue. A zone of fibrinous pneumonia surrounds these bronchi and fissures in the bronchial wall penetrate into this zone. One dilated bronchus 2.4 mm. in diameter with no cartilage in its wall has vascular connective tissue covered by epithelium on one side, whereas the remainder of the circumference is formed by exposed alveoli filled with fibrin, the bronchial wall having disappeared. A section through a part of the abscess which has been mentioned shows a very irregularly formed cavity approximately 1 x 0.7 cm. Remains of bronchial wall, consisting of very vascular tissue covered by flat epithelium in several layers, indicate the origin of the cavity. Between these remnants of bronchi deep pockets extend into the pulmonary tissue which in the margin of the cavity is the site of fibrinous pneumonia. In one place, in contact with the cavity, a wide area of consolidated tissue has undergone necrosis and both alveolar walls and their contents have lost their nuclei. Leucocytes which are accumulating at the margin of the necrotic patch form a line of demarcation between living and dead tissue.
Abscess may be the result of the profound changes which occur in the bronchi as the result of influenza. Necrosis caused by bacteria within the bronchi weakens and in places destroys the wall. Bacteria penetrate into the surrounding tissue and hemolytic streptococci (or staphylococci) may produce localized abscesses. These abscesses are usually situated near the pleural surface of the lung, because destructive changes causing rupture of the bronchial wall occur more frequently in the smaller peripheral bronchi than in the larger bronchi containing cartilage. Abscesses occur more frequently at the bases of the lungs, because the most severe changes in the bronchi occur in the dependent part. (See “Bronchiectasis,” p. [240].)
Healing of Abscess.—The following autopsy is of interest in relation to the treatment of pulmonary abscess and associated empyema.
Autopsy 467.—P. C., white, aged twenty-five, a farmer from Missouri, had been in military service three months. Illness began September 27, thirty days before death, and the patient was admitted the day following onset with headache, backache and cough. Pneumonia with consolidation in the right lower lobe was recognized on the sixth day of illness. On the ninth day 500 c.c. of fluid were withdrawn from the right pleural cavity; there were cyanosis and dyspnea. On the eleventh day 700 c.c. of fluid were withdrawn. On the twelfth day thoracotomy was performed and 100 c.c. of greenish fluid were removed. The patient’s condition improved for a time, but on the twenty-sixth day 1,000 c.c. of straw colored fluid were aspirated from the left pleural cavity and on the twenty-eighth day the same amount of seropurulent fluid was withdrawn.
Anatomic Diagnosis.—Healing abscess of right lower lobe communicating with the pleural cavity; acute purulent pleurisy with closed thoracotomy wound on the right side; purulent pleurisy on the left side; acute bronchopneumonia with lobular consolidation in the left lung; purulent bronchitis; bronchiectasis with formation of spherical bronchiectatic cavities; acute splenic tumor.
At the base of the right chest is a closed thoracotomy wound 2 cm. in length; the right pleural cavity contains 200 c.c. of thick creamy pus and the cavity is lined by a thick tough membrane. The left pleural cavity contains 800 c.c. of white purulent fluid thinner than that on the right side. The right lung is compressed into the posterior and inner part of the chest. The upper lobe is pink and air containing; the posterior and lower part of the lower lobe is red and atelectatic, and fibrous septa are more conspicuous than elsewhere. The pleura of the external surface near the basal edge, in an area 2 cm. across, is depressed and yellowish gray in color. In the center of this area is a small opening communicating with a pocket 0.5 cm. across within the substance of the lung.
In the lower lobe beneath the interlobular surface are two spherical bronchiectatic cavities, each about 1.5 cm. across, with smooth lining in continuity with two branches of the same bronchus of medium size.
Bacteriologic examination showed the presence of S. hemolyticus in the blood of the heart. No growth was obtained from the left lung; the left pleural cavity contained hemolytic streptococci and S. aureus, the latter in small number. S. hemolyticus and B. influenzæ were grown from the left main bronchus.
A microscopic section through the abscess and its communication with the pleura shows that its cavity contains polynuclear leucocytes and the wall is formed by granulation tissue covered by fibrin. Some alveoli outside the abscess contain compact balls of fibrin containing a few fibroblasts; this fibrin stains deeply with hematoxylin as if it contained calcium. The surface of the lung is covered by fibrin in process of organization.
In the foregoing instance a pulmonary abscess on the right side has ruptured into the pleura and, completely separated from the adjacent lung by a wall of newly formed tissue, is in process of healing. It shows that these pulmonary abscesses below the pleura may heal provided drainage is established by rupture into the pleural cavity and subsequent evacuation of pleural exudate. It is noteworthy that in this instance empyema extended from the right to the left pleural cavity, both S. hemolyticus and S. aureus were found at autopsy. The thoracotomy wound on the right side was closed at autopsy.