Drug-resistant TB shows abnormalities on CT

Micronodules, tree-in-bud appearance, consolidations, cavities, bronchiectasis, and lobular consolidations are frequent CT abnormalities of extensively drug-resistant tuberculosis.

Dr. Eun Sun Lee from the Seoul National Hospital in Korea and colleagues made these determinations by retrospective review of microbiological results and drug sensitivity tests of 260 patients. They had been diagnosed with multidrug-resistant tuberculosis (MDR-TB) from 1994 to 2005.

The researchers found that 47 patients had extensively drug-resistant tuberculosis and the other 213 patients had multidrug-resistant TB. CT examinations were performed on 20 of the 47 drug-resistant TB patients and 85 of the 213 multidrug-resistant TB patients.

Early identification and isolation of drug-resistant TB patients is crucially important, and CT examination may help evaluate extent of disease and establish a treatment plan, according to Lee.

Two radiologists reviewed the CT studies looking for the presence and extent of micronodules, tree-in-bud appearance, lobular consolidation, consolidation, cavity, bronchiectasis, pleural effusion, lymphadenopathy, bronchopleural fistula, and emphysema.

The most frequent CT abnormalities were micronodules and tree-in-bud appearance, seen in all of the drug-resistant TB patients. CT revealed consolidations, cavities, or bronchiectasis in about eight of 10 drug-resistant TB patients. Lobular consolidations appeared in 70%.

Lymphadenopathy (45%), pleural effusion (25%), emphysema (15%), and bronchopleural fistula (10%) were less frequent CT abnormalities. Compared with multidrug-resistant TB patients, subjects with drug-resistant TB showed a significantly larger extent of tree-in-bud appearance and consolidations. There were no significant differences between the two types of TB with respect to other CT features, according to the researchers.

"The CT findings they describe are suggestive of TB of any variety but can also be seen less often in non-TB infections," said Dr. Gerald F. Abbott, a thoracic radiologist at Massachusetts General Hospital.

Drug-resistant TB is a serious problem and troubling public health issue. If a radiologist recognizes the findings Lee and colleagues describe, the radiologist would assume there is an infection and should give serious consideration to the possibility of TB, Abbott said.

Drawbacks of the study, presented at the 2008 RSNA meeting, include lack of an easy way to differentiate typical tuberculosis from drug-resistant tuberculosis, he said.

Consolidation and tree-in-bud appearance can be found in aspiration pneumonia and some other entities, Abbott said.

For more information from the Diagnostic Imaging and SearchMedica archives:

Optical imaging opens a new window on tuberculosis diagnosisChest x-ray remains crucial for finding drug-resistant TBDrug-resistant TB story illustrates global challenge for radiology