Role of HRCT in the identification of atypical pulmonary mycobacteriosis.

Aim: 1) To identify the principal radiological signs of atypical pulmonary mycobacteriosis by means of X-rays and CT/HRCT; 2) to compare the two methods in order to evaluate their reliability with particular interest for the diagnostic role of HRCT in the identification of the disease; 3) to establish any significant differences in the pathology between AIDS and immunocompetent patients.

Material And Methods: The chest X-rays and CT/HRCT of 28 atypical pulmonary mycobacteriosis patients (16 with AIDS and 12 immunocompetent) have been studied. The subjects were examined during the period of October 1993 to May 2000 and were found to be positive for atypical mycobacterium and consequently underwent a standard chest X-ray. Twenty cases were followed-up with a chest CT/HRCT; of these only 17 were performed within 30 days of the traditional chest X-ray which was considered to be the time limit in order to validate the comparison between the two methods.

Results: The significant semeiotical findings were the parenchymal consolidations observed in 25 patients (89%) by standard chest X-rays; the CT/HRCT confirmed the findings in 4 cases while in 13 it enhanced the evaluation of their extensions. In 9 cases the standard chest X-ray established the presence of cavitations which were confirmed by the CT/HRCT in only 7 cases. Lymphadenopathy was observed in 3/28 patients (10.7%) through standard X-rays and in 15/17 cases (82%) through CT/HRCT. The latter method revealed to be extremely useful in the identification of this pathology. Nodules and micronodules were seen in 5 patients with traditional X-rays and in 9 cases with CT/HRCT. Bronchogenic spread signs of disease became visible only with CT and in particular with HRCT (11/17 patients = 65%). Comparing the two groups (AIDS and immunocompetent) taken into consideration, the most frequent lesion present in both was parenchymal consolidation resulting more bilateral in the AIDS subjects. Cavitation and pleural edema were seen more often in the AIDS group while bronchiectasia, bronchogenic spread and signs of previous pleuro-parenchymal suffering were more frequent in the immunocompetent patients. Lymphadenopathy was frequently found in the total study population but appeared slightly prevalent for the group not afflicted with AIDS.

Conclusion: Radiological study of the chest permitted the identification of signs useful in the diagnosis of mycobacteriosis in all the patients studied. The application of CT/HRCT added helpful elements in almost all of the cases examined demonstrating to be more effective than the standard chest X-ray not only in terms of improved evaluation of known lesions but also in the identification of lesions which are difficult to determine by means of traditional radiology.