PULMONARY MYCOBACTERIUM-KANSASII INFECTION - COMPARISON OF RADIOLOGICAL APPEARANCES WITH PULMONARY TUBERCULOSIS

Background - A study was undertaken to determine if there are differen ces in the radiological appearances at presentation between pulmonary infections caused by Mycobacterium kansasii and Mycobacterium tubercul osis. Correct recognition of the organism has important implications w ith regard to initial therapy and contact tracing. Methods - The initi al chest radiographs of 28 patients with pulmonary M kansasii infectio n were compared with those of 56 age, sex, and race matched patients w ith ill tuberculosis infection. All patients in both groups were cultu re positive and none was known to be HIV positive. The radiographs wer e analysed independently by two radiologists who were unaware of the c ausative organism. Results - Radiographic abnormalities in patients wi th M kansasii infection were more frequently unilateral and right side predominant, while those with tuberculosis more frequently involved a lower lobe. Air space shadowing involving more than one bronchopulmon ary segment and pleural effusions were seen less frequently in M kansa sii infection (four of 28 (14%) versus 30 of 56 (54%) and none of 28 v ersus 15 of 56 (27%)). Cavitation (21 of 28 (75%) versus 34 of 56 (61% )) was seen to a similar extent in patients with M kansasii infection and in those with tuberculosis. Cavities tended to be smaller in patie nts with M kansasii infection (p < 0.01). Conclusions - Differences ar e seen in the radiographic appearances of pulmonary infection caused b y M Kansasii and M tuberculosis. These differences are not sufficient to allow a positive diagnosis on the basis of radiographic findings al one, but the presence of a pleural effusion or lower lobe involvement makes M kansasii infection very unlikely.