Diversity of X-ray Findings in TB

December 31, 2006

Q:What is the most common radiographicpresentation of pulmonary tuberculosis (TB)among persons with HIV infection?

Q:What is the most common radiographicpresentation of pulmonary tuberculosis (TB)among persons with HIV infection?A:The radiographic manifestations of TB are extremelyvariable (Table) both in the general populationand in those with HIV infection.1,2 The classic presentationconsists of apical infiltrates with or without cavitary formation,but there are many others. A unilateral exudativepleural effusion is also common (Figure 1).Bilateral pleural effusions, which are extremely rarein TB, are a manifestation of disseminated disease. Parenchymalconsolidation in any lobe (Figure 2) or rightmiddle lobe atelectasis (Figure 3) are other possible findings.Another variation is miliary TB, which can have avery subtle presentation. Very tiny shadows--often smallerthan millet seeds--are evenly distributed throughoutboth lungs. This is an emergent situation that requires immediateconfirmation by smear or culture and prompttreatment, even before the cultures have time to grow. CTmay help identify miliary TB with greater sensitivity thanstandard chest radiography.Lower lobe chronic infiltrates are sometimes seen inthe elderly and are often present in persons with diabetes.Suspect TB in an older person when an infiltrate does notresolve.TB is rarely the diagnosis if the posteroanterior andlateral chest radiographs have no clinically significantparenchymal shadows. However, normal or near-normalradiographic findings may be associated with isolatedendobronchial TB. This condition is most commonlyfound in children from countries where TB is prevalent;it is occasionally seen in adults in the United States.3Persons with HIV infection or AIDS. These patientsoften do not present with classic radiographic findings. TheTB manifestations in HIV-positive patients are a function ofthe degree of immunosuppression. Upper lobe infiltrates aregenerally present in patients with a positive tuberculin skintest, which is a manifestation of intact cell-mediated immunityand relatively preserved CD4 T-cell counts. Cavitation isless common in patients with AIDS, but it may be present inadvanced disease. In more immunosuppressed patients,adenopathy (Figure 4) and pleural effusions are frequentfindings, along with chronic infiltrates in the upper or lowerlobes. Interstitial infiltrates indistinguishable from Pneumocystiscarinii are sometimes present. Normal chest radiographsare found in 12% to 14% of HIV-infected patients.4Confirming the diagnosis. No radiographic patternis absolutely diagnostic of TB. Infections attributable toother closely related organisms, such as Mycobacteriumavium-intracellulare and Mycobacterium kansasii, oftenhave similar radiographic presentations, as do some fungalinfections. Thus, the diagnosis of TB must always beconfirmed bacteriologically.




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