Sequestration of the lung.

The condition of an abnormal pulmonary artery supplying a sequestrated segment is not well known although more than 30 cases have been described. The fact that these cases have come from a few centres (Pryce, 1946; Pryce, Sellors and Blair, 1947; Butler, 1947; Douglass, 1948; Bruwer, Claggett and McDonald, 1950; McDowell, Robb, Hinds and Nicks, 1951; Kergin, 1952; McDowell, Robb and Indyk, 1955) suggests that the condition may not be as rare as is believed. Once infected the sequestrated lobe is the cause of a chronic and disabling illness which can be completely cured by surgery and therefore merits attention. Pryce (1946) and Pryce, Holmes Sellors and Blair (1947) fully described the condition and were first to publish eight cases successfully treated by surgery. The condition consists of a large artery arising from the abdominal or thoracic aorta, and entering the lung in the region of the diaphragm to supply a sequestrated or dislocated portion of the lung. The tissue in this ectopic piece of lung consists of normal pulmonary elements, with bronchi which are not in continuity with the bronchi of the normal lung. In some cases there are infective changes present with associated bronchiectasis. In others the tissue is largely cystic. The abnormal artery may (1) supply normally connected lung, (2) supply the sequestrated mass and normal lung, and (3) supply only the mass. The artery is elastic and is a pulmonary artery. Because of its origin from the aorta the pressure in this vessel is higher than in a normal pulmonary artery and arteriosclerotic changes are not infrequent even when the normal pulmonary vessels show no such change. Infective changes in the tissue supplied may predispose toward this sclerosis. Apart from this abnormal artery the cardiovascular system is normal. The blood leaves the abnormal segment by the pulmonary veins. In the articles by Pryce (1946) and Pryceet al. (1947) the development of the ectopic tissue is discussed: the abnormal vessel is the primary malformation and Pryce and his fellow workers suggest that sequestration is the result of traction exerted through the capillaries of the adventitious blood supply in the developing lung. In their opinion infection of the mass probably occurs by direct spread from a pneumonic process in the adjacent lung, perhaps occasionally from the blood stream. The persistence of infection, which sometimes proceeds to suppuration, appears to be due to lack of adequate bronchial drainage. Cases usually present as recurrent pneumonia, empyema, cysts or bronchiectasis. The abnormal vessel, especially if arising from the abdominal aorta, may not be easily seen at operation, and, if unsuspected, fatal haemorrhage may result. The present case is described as it shows some interesting features.