The so-called middle lobe syndrome.

Chronic atelectasis and pneumonia of the middle lobe have been described as a clinical syndrome, of which the essential pathological feature is an obstruction of the middle lobe bronchus. The cause of obstruction may be intraluminal or extraluminal, specific causes such as tumour or active tuberculosis not included. Graham, Burford, and Mayer (1948) reported 12 cases in which the syndrome resulted from enlargement of lymph nodes surrounding the middle lobe bronchus causing compression of the bronchial lumen and inflammatory changes with constriction. The chief symptoms were haemoptysis and recurrent pneumonia with intervening periods of malaise and weakness. The reason for the middle lobe being affected more frequently than other lobes is, according to Brock (1946, 1950), that the middle lobe bronchus is exceptionally long and narrow and surrounded by lymph nodes draining not only the middle lobe but the lower lobe as well. Brock (1950) has also shown that a lymph node situated just below the middle lobe bronchus is the one most frequently involved and that previous tuberculous infection is the commonest cause of the lymphadenopathy. The infection causes tuberculous lymphadeniti-, which, in turn, may give rise to caseous necrosis with deposition of lime salts resulting in a peri-bronchial fibro-is and constriction of the middle lobe bronchus. In some instances perforation and stricture may occur, in others broncholiths. The result will be atelectasis, infection, fibrosis, bronchi-ectasis. Brock calls this "the post-tuberculous middle lobe syndrome," and states that it occurs twice as often as similar involvement of the remaining parts of the lungs. Non-specific broncho-stenosis, as described by Leegaard (1945), Fabritius and 0degaard (1948), and Paulson and Shaw (1949), may produce a similar clinical picture. Broncho-genic carcinoma arising in the middle lobe bronchus is, according to Brock, a rare occurrence. During the past five years 40 cases of post-tuberculous or non-specific bronchostenosis have been admitted in the Surgical Department A of the University Hospital, Oslo. Among these cases middle lobe involvement was observed in 19, which are analysed in the present paper. AETIOLOGY An analysis (Table I) of the individual cases showed that seven of the patients presented clear-cut symptoms of previous tuberculous infection as indicated by the presence of tuberculous allergy and calcified lesions