Microscopic examination shows that the epithelium of the bronchi is partially or completely destroyed and that destruction of the underlying tissue, with acute suppurative inflammation, penetrates to a greater or less depth into the wall. When the epithelium of the bronchus is wholly destroyed and the lumen is filled and distended with polynuclear leucocytes, a cross section of the tube has the appearance of a small abscess; but more careful examination often shows that the engorged mucosa is still intact. Occasionally, a network of fibrin forms a layer covering the denuded mucosa. Disintegration of the superficial tissue may extend to the muscularis or through it, and may penetrate the wall of the bronchus. The tissue in contact with the exposed surface contains many polynuclear leucocytes and blood vessels plugged with fibrinous thrombi, but deeper in the tissue lymphoid and plasma cells are more numerous. In 2 instances (Autopsies 286 and 425) favorable sections have demonstrated that the wall of an abscess on one side consists of the remains of a bronchus, covered by epithelium composed of squamous cells, Whereas the remainder of the wall, here very irregular, is formed by partially destroyed alveoli plugged with fibrin. The suppurative process has penetrated the wall of the bronchus on one side and extended into the surrounding alveolar tissue. In other instances, abscess cavities occur within the alveolar tissue of the lung and their relationship to bronchi is not evident. In the mass of polynuclear leucocytes which fill the abscess cavity, are clumps of staphylococci in great abundance, usually forming characteristic colonies which are conspicuous with the low power of the microscope.
Empyema, Pericarditis and Peritonitis
No sharp line can be drawn between nonpurulent and purulent pleurisy. A diagnosis of empyema has been made when the fluid in the chest has become opaque and fibrin has undergone softening or solution. The lesion has been designated seropurulent when there has been abundant thin, opaque, gray fluid. Pleurisy has been designated fibrinopurulent when the cavity has contained opaque fluid and ragged soft white or yellowish fibrin adherent to the chest wall; this fibrin is evidently in process of disintegration and there may be numerous shreds and flakes of fibrin which subside to the bottom of the fluid. The amount of fluid in the cavity may occasionally exceed 1,700 c.c.; that in both pleural cavities may exceed 2,500 c.c. The lesion has been designated purulent when fibrin has almost wholly disappeared and the cavity contains thick yellowish white fluid. In 4 of 5 instances in which thoracotomy had been performed, empyema has assumed this otherwise uncommon type.
Some inflammation of the pleura is almost constantly found in association with all forms of pneumonia, but in many instances is so slight that it has no noteworthy significance. Table L shows the incidence of various types of pleurisy.
| Table L | ||||||||
|---|---|---|---|---|---|---|---|---|
| LOBAR PNEUMONIA | BRONCHOPNEUMONIA | SUPPURATIVE PNEUMONIA WITH ABSCESS | INTERSTITIAL SUPPURATIVE PNEUMONIA | |||||
| No. | % | No. | % | No. | % | No. | % | |
| No pleurisy noted | 30 | 46.9 | 44 | 55 | 1 | 2.6 | 1 | 5.9 |
| Serous pleurisy | 5 | 7.8 | 9 | 11.2 | ||||
| Fibrinous pleurisy | 10 | 15.6 | 5 | 6.2 | 1 | 2.6 | ||
| Serofibrinous pleurisy | 12 | 18.2 | 14 | 17.5 | 3 | 7.7 | ||
| Seropurulent pleurisy | 9 | 23.1 | 1 | 5.9 | ||||
| Fibrinopurulent pleurisy | 7 | 10.9 | 5 | 6.2 | 17 | 43.6 | 12 | 70.6 |
| Purulent pleurisy | 3 | 3.7 | 8 | 20.5 | 3 | 17.6 | ||
| Total | 64 | 80 | 39 | 17 | ||||
Empyema has occurred, on the one hand, in 12.4 per cent of instances of lobar pneumonia and in 9.9 per cent of instances of bronchopneumonia alone. It has occurred, on the other hand, in 87.2 per cent of instances of suppurative pneumonia with abscess formation and in 94.1 per cent instances of interstitial suppurative pneumonia. These suppurative lesions are caused by hemolytic streptococci, and when cultures are made from the pleural exudate this microorganism is isolated.
Of 16 instances in which empyema has occurred in association with lobar pneumonia or bronchopneumonia unaccompanied by suppuration in 6 there has been infection with hemolytic streptococci. Empyema has occurred in the absence of hemolytic streptococci only 10 times.
Empyema Caused by Hemolytic Streptococci.—When necrosis preceding abscess formation has occurred in the lung, streptococci are found in immense numbers in the dead tissue. The pleura overlying the abscess undergoes necrosis and occasionally streptococci are particularly numerous upon the pleural surface of the necrotic tissue. In Autopsy 376 a membrane thin as tissue paper, representing the pleura, separated an abscess containing thick pus from the pleural cavity which was the site of empyema. The abscess may rupture into the pleural cavity and at the same time may be in free communication with a bronchus (Autopsy 480). In one (Autopsy 467) instance an abscess which had ruptured into the pleural cavity had completely discharged its contents and was in process of healing, newly formed fibrous tissue being abundant in its wall.
With few exceptions empyema has accompanied subpleural abscess caused by hemolytic streptococci, being found on the side corresponding to the abscess. Among 39 instances of pulmonary abscess, empyema has been limited to the side of the abscess in 23; it has been present on the opposite side as well in 10 instances. In 2 instances there have been abscesses in both lungs; in one (Autopsy 385 A) there has been double empyema, and in the other (Autopsy 487) empyema only on the left side. In one instance abscess has been recognized by microscopic examination and its location is not recorded. In 5 instances of abscess formation there has been no empyema. In Autopsy 383 there has been no pleurisy noted; in Autopsy 416 there has been fibrinous pleurisy and in Autopsies 277, 290 and 380, serofibrinous pleurisy.
Empyema has been almost invariably found in association with interstitial suppurative pneumonia. This lesion extends by way of the lymphatics up to the pleural surface and is often more conspicuous just below the pleura than elsewhere. Empyema has been absent in only 3 of 21 examples of the lesion and in one of these there has been serous effusion. In 12 instances interstitial suppuration has occurred only on one side and empyema has been limited to this side; in 5 instances with interstitial suppuration on one side there has been empyema on both sides; in 2 instances with interstitial suppuration in both lungs there has been double empyema.