Morphometrical, histopathological, immunohistochemical, and ultrastructural findings in human pulmonary tissue destruction following penetrating low-velocity firearm injuries to the lungs.

This autopsy-based study investigated the morphological correlates of pulmonary tissue destruction following fatal penetrating gunshot wounds to the lungs using morphometry, histology, immunohistochemistry, and scanning electron microscopy on whole human lungs fixed-expanded via formalin inflation. As the residue of temporary cavity formation, mantle-like hemorrhagic destruction zones were seen surrounding the missile track that showed an eccentric, conical extension enlarging toward subpleural lung segments. In addition, circumscribed, satellite-like bleeding zones at distances of up to 5.5 cm beyond the border of the permanent cavity were observed that corresponded to interstitial perivascular hemorrhages around larger and smaller pulmonary vessels on the micro-morphological level. These multifocal hemorrhages within macroscopically unaffected parts of pulmonary tissue at some distance from the actual missile track may represent unrecognized, life-threatening intrapulmonary bleeding sources in survivors, potentially leading to ventilation-perfusion mismatch and progressive lung failure. A further noticeable microscopic and ultrastructural finding was that of club-shaped distensions of ruptured alveolar septa strictly limited to the extent of the temporary cavity. These club-shaped distensions of ruptured alveolar septa seem to represent a special feature of alveolar architectural damage that can be explained by the dynamics of the temporary cavity formation: the radial acceleration and overdistension of tissue during temporary cavitation initiates stretch mechanisms of the displaced tissue, causing the alveolar septa to rupture with subsequent foreshortening and pursing of elastic alveolar fibers.