Tuberculosis radiology

Radiology (X-rays) is used in the diagnosis of tuberculosis. Abnormalities on chest radiographs may be suggestive of, but are never diagnostic of TB, but can be used to rule out pulmonary TB.

Chest X-ray
A posterior-anterior (PA) chest X-ray is the standard view used; other views (lateral or lordotic) or CT scans may be necessary.

In active pulmonary TB, infiltrates or consolidations and/or cavities are often seen in the upper lungs with or without mediastinal or hilar lymphadenopathy. However, lesions may appear anywhere in the lungs. In HIV and other immunosuppressed persons, any abnormality may indicate TB or the chest X-ray may even appear entirely normal.

Old healed tuberculosis usually presents as pulmonary nodules in the hilar area or upper lobes, with or without fibrotic scars and volume loss. Bronchiectasis and pleural scarring may be present.

Nodules and fibrotic scars may contain slowly multiplying tubercle bacilli with the potential for future progression to active tuberculosis. Persons with these findings, if they have a positive tuberculin skin test reaction, should be considered high-priority candidates for treatment of latent infection regardless of age. Conversely, calcified nodular lesions (calcified granuloma) pose a very low risk for future progression to active tuberculosis.

Abnormalities on chest radiographs may be suggestive of, but are never diagnostic of, TB. However, if a person has a positive response to the tuberculin skin test and no symptoms of the disease, chest radiographs can be used to rule out the possibility of pulmonary TB.

CDC guidelines for evaluating CXR
The chest X-ray and classification worksheet by the Centers for Disease Control and Prevention (CDC) of the United States is designed to group findings into categories based on their likelihood of being related to TB or non-TB conditions needing medical follow-up.

Normal findings
These are films that are completely normal, with no identifiable cardiothoracic or musculoskeletal abnormality.

Chest X-ray findings that can suggest active TB
This category comprises all findings typically associated with active pulmonary TB. In the US, refugees or immigration applicants with any of the following findings must submit sputum specimens for examination.

1. Infiltrate or consolidation - Opacification of airspaces within the lung parenchyma. Consolidation or infiltrate can be dense or patchy and might have irregular, ill-defined, or hazy borders.

Chest X-ray findings that can suggest inactive TB
This category includes findings that are suggestive of prior TB, that is inactive. Assessments of the activity of TB cannot be made accurately on the basis of a single radiograph alone. If there is any question of active TB, sputum smears must be obtained. Therefore, any applicant might have findings grouped in this category, but still have active TB as suggested by the presence of signs or symptoms of TB, or sputum smears positive for AFB.

The main chest X-ray findings that can suggest inactive TB are:

1. Discrete fibrotic scar or linear opacity—Discrete linear or reticular densities within the lung. The edges of these densities should be distinct and there should be no suggestion of airspace opacification or haziness between or surrounding these densities. Calcification can be present within the lesion and then the lesion is called a "fibrocalcific" scar.

Follow-up needed
This category includes findings that suggest the need for a follow-up evaluation for non-TB conditions.


 * 1) Musculoskeletal abnormalities - New bony fractures or radiographically apparent bony abnormalities that need follow-up.
 * 2) Cardiac abnormalities - Cardiac enlargement or anomalies, vascular abnormalities, or any other radiographically apparent cardiovascular abnormality of significant nature to require follow-up.
 * 3) Pulmonary abnormalities - Pulmonary finding of a non-TB nature, such as a mass, that needs follow-up.
 * 4) Other - Any other finding that the panel physician believes needs follow-up, but is not one of the above.

No follow-up needed
This category includes findings that are minor and not suggestive of TB disease. These findings require no follow-up evaluation.
 * 1) Pleural thickening - Irregularity or abnormal prominence of the pleural margin, including apical capping (thickening of the pleura in the apical region). Pleural thickening can be calcified.
 * 2) Diaphragmatic tenting - A localized accentuation of the normal convexity of the hemidiaphragm as if "pulled upwards by a string."
 * 3) Blunting of costophrenic angle (in adults)—Loss of sharpness of one or both costophrenic angles. Blunting can be related to a small amount of fluid in the pleural space or to pleural thickening and, by itself, is a non-specific finding (except in children, when even minor blunting may suggest active TB). In contrast a large pleural effusion, or the presence of a significant amount of fluid in the pleural space, may be a sign of active TB at any age.
 * 4) Solitary calcified nodules or granuloma - Discrete calcified nodule or granuloma, or calcified lymph node. The calcified nodule can be within the lung, hila, or mediastinum. The borders must be sharp, distinct, and well defined. This was considered a Class B3 TB in the past; however, Class B3 has been omitted from the classification scheme because it has not been found to be associated with active TB.
 * 5) Minor musculoskeletal findings - Minor findings needing no follow-up.
 * 6) Minor cardiac findings - Minor findings needing no follow-up.

Extrapulmonary tuberculosis


Peritoneal tuberculosis may mimic peritoneal carcinomatosis on CT scan.

There is low-quality evidence that abdominal ultrasound has 63% sensitivity and 68% specificity in diagnosing abdominal tuberculosis when tuberculosis is bacteriologically confirmed in HIV-positive individuals. Therefore, a negative abdominal ultrasound finding does not rule out the disease due to its low sensitivity.