Linear and Similar X-Ray Hieroglyphs

Abstract

Since the discovery of the x-rays in 1895 a great deal of individual and concerted endeavors have brought about interpretation of linear shadows of x-rays of the chest which represent normal entities or pathologic manifestations. One of the best known eponyms relative to abnormal pulmonary x-ray shadows is represented in Kerley A and B lines (Kerley, P, in Shanks, S C and Kerley, P: A Textbook of X-Ray Diagnosis (2-nd ed), London, Lewis, H K, 1951). The A lines which extend from the peripheral to the central lung fields are visualized as the result of accumulation of transudate in the pulmonary interstitial spaces and of distention of lymphatics in the interlobar septa in patients with chronc pulmonary venous hypertension. Too, they may be seen in instances when interlobular lymphatics are filled with tumor cells. Kerley B lines, localized in the peripheral basal lung areas, portray thickened edematous interlobular septa together with their lymphatic channels and veins. Also, their visualization has been attributed to dense hemosiderin particles, mineral dust particles, tumor cells, sarcoid changes, and fibrosis. Another well-deserved eponym is attached to the term Fleischner’s plate-like atelectasis (Am J Roentgenol 46:610, 1941; in Rabin, C B: Roentgenology of the Chest, Springfield, Thomas C C, 1958). X-ray shadows of this category are usually 1-3 cm above the diaphragm. They may be unilateral or bilateral, single or multiple, from hair-like appearance to a diameter of 5 mm. Usually they are evanescent unless fibrotic transformation replaces atelectasis. Fleischner’s plaques may be brought about by ponopnea in connection with chest trauma, rib fracture, costochondral separation, inflammatory diseases of the pleura, chest wall, diaphragm, acute abdominal disease and neoplasia of abdominal organs. Other possible causal factors include bronchial occlusion by exudate, compression or spasm, pulmonary embolism, encapsulated pleural effusion, injury to the spinal cord, poliomyelitis, neuromuscular anomalies, such as amyotonia congenita, severe shock, and rarely myocardial infarction. Fleischner’s pertinent comment is worth remembering. “Plate atelectasis may accompany a distinct infarct, it may precede the formation or recognition of infarcts, or it may appear where no infarct is formed at all. Thus plate atelectasis may be an early or the only roentgen sign suggesting pulmonary embolism.” In some instances x-ray evidence of infarction may not be detectable until 12 hours after the event. Even then pathologic changes may be incomplete and associated with transient hemorrhage and edema. Subsequently necrosis and fibrosis may develop with a linear scar. One must be aware of short or extended arcuate lines which may signify eventration of the diaphragm or diaphragmatic hernia. Occasionally in the basal areas of the chest tenting of the diaphragm may be observed. Evanescent tenting may result from transient basal atelectasis of limited extent. Polyarcuate (scaloping or double-contour) outline of the diaphragm may be seen at the anterior and middle parts of this structure in patients with bronchial asthma, bronchitis, emphysema, and pulmonary fibrosis. It results from sequential rather than simultaneous contraction of the component muscle bundles of the diaphragm. Scimitar syndrome is observed in x-ray films as a crescent-like paracardiac shadow cast by an aberrant pulmonary vein which drains into the vena cava. At the site of the minor interlobar fissure the pleura may be visualized as a discrete line or closely set parallel short lines. Occasionally pleura separating the lingula or some of the lung segments may be observed. In pneumomediastinum the pleura is delineated by a thin cephalo-caudal line. Miniature pear-shaped shadow of the azygos vein may be observed close to the right border of the upper mediastinum in about 0.4 percent of chest x-rays.