Hydatid disease of the lung.

Lendon (1902) pointed out that, although it had been generally assumed that the cavity in the lung left after removal of a hydatid cyst soon becomes obliterated,'this was not by any means invariable. He described two cases in which a pulmonary cavity was found at necropsy some time after complete expulsion of the hydatid membranes by coughing. Dew (1928) stated that in some cases in which the cyst was large or the adventitia thick, particularly when it was situated in the upper part of the lungs, complete collapse of the cavity and re-expansion of the lung did not occur. In an article based on sixteen cases of bilateral pulmonary cysts from the Australasian Hydatid Registry, Christie (1938) stated that when the cyst had thin walls and was not infected, obliteration of the lung cavity soon took place. In patients radiographed at intervals of four months, ten months, and four years respectively after removal of the cyst, no evidence of a residual cavity was seen. In a bilateral infected case there was no evidence'of residual cavitation after seven months. Writing of the pulmonary cavity, Barrett (1947) stated that it was usually quickly obliterated after removal of the parasite. If it persisted for as long as six months it was likely to be permanent and to become lined with bronchial epithelium. Such a lung cyst might remain for years without causing symptoms, but the possibility of haemorrhage from it or infection within it was always present. The type of case in which the pulmonary cavity was likely to persist was that in which the adventitia was thick and tough at the time of operation. Those cases in which inflammation had occurred around a simple hydatid, or in which