Tuberculosis

Primary Pulmonary Tuberculosis

• Parenchyma

§   Upper lobes affected slightly more than lower

§       Alveolar infiltrate

§       Cavitation is rare

§   Lobar pneumonia is almost always associated with lymphadenopathy—therefore, lobar pneumonia associated with hilar or mediastinal adenopathy at any age should strongly suggest TB

• Lymph node

§   Mostly unilateral hilar and/or paratracheal, usually  right sided, rarely bilateral

§      Differentiates primary from postprimary TB—it does not occur in postprimary TB

§       Much more common in children

·       Airway

·    Atelectasis classically affects the anterior segments of the upper lobes or the medial segment of the RML

·       Pleura

§       Pleural effusion as a manifestation of primary TB occurs more often in adults than children

§       With appropriate treatment, it carries the best prognosis of all patterns of TB and is the least likely to develop complications

§      The fluid accumulates slowly and painlessly—therefore, patients with TB are seldom seen with a small amount of pleural fluid

§       Parenchymal disease will almost never be present with a pleural effusion although lymphadenopathy may

§   Apical pleural scarring is rarely tuberculous in origin

• Calcification in the primary complex is relatively rare.

• Very few patients with primary TB have clinical manifestations

Postprimary Tuberculosis (“Reactivation TB”)

• Most cases in adults occur as reactivation of a primary focus of infection acquired in childhood

• Limited mainly to the apical and posterior segments of the upper lobes and the superior segments of the lower lobe

• Caseous necrosis and the tubercle (accumulations of mononuclear macrophages, Langerhan's giant cells surrounded by lymphocytes and fibroblasts) are the pathologic hallmarks of postprimary TB

• Healing occurs with fibrosis and contraction; calcification is rarer than in primary

Patterns of distribution

§       Almost always affect the apical or posterior segments of the upper lobes or the superior segments of the lower lobes—bilateral upper lobe disease is very common

§       May present as pneumonia

§       Cavitation may result: the cavity is usually thin-walled, smooth on the inner margin with no air-fluid level

Tuberculosis, Cavitary. There are large cavities in both apices (white arrows) and airspace disease at the left base (yellow arrow) on the chest radiograph. On the coronal CT, the thin-walled upper lobe cavities without air-fluid levels are again seen (blue arrows) as is the consolidation at the left base (green arrow). Nodular densities are scattered throughout both lungs.

§       Transbronchial spread may occur—from one upper lobe to opposite lower or to another lobe

§       Miliary spread (below)

§       Bronchiectasis—usually asymptomatic

§       Bronchostenosis due to fibrosis and stricture: fibrosis may cause distortion of a bronchus and atelectasis many years after the initial      infection—“middle lobe syndrome”

§       Solitary pulmonary nodule—the tuberculoma—may occur in either primary or postprimary disease; round or oval lesions with small, discrete shadows in the immediate vicinity of the lesion—the “satellite” lesion

• Formation of a pleural effusion in postprimary TB almost always means direct spread of the disease into the pleural cavity and should be regarded as an empyema—this carries a graver prognosis than the pleural effusion of the primary form

• Direct extension into the ribs or sternoclavicular joints is uncommon

Miliary Tuberculosis

• Older men, Blacks and pregnant women are susceptible

• Onset is insidious

• Fever, chills, night sweats are common

• Takes weeks between the time of dissemination and the radiographic appearance of disease

• Considered to be a manifestation of primary TB–although clinical appearance of miliary TB may not occur for many years after initial infection

• When first visible, they measure about 1 mm in size; they can grow to 2-3mm if left untreated

• When treated, clearing is rapid—miliary TB seldom, if ever, produces calcification

TB and Other Diseases

• There is an association between TB and silicosis, TB and HIV

• There may be an association between TB and sarcoid

• There is no association between TB and bronchogenic carcinoma

HIV and TB

• No matter what form of TB the patient has, it tends to look like 1° TB

• Hilar and mediastinal adenopathy are common

• Cavitation is less common

• There is no predilection for the apices

• MAI (mycobacterium avium-intracellulare) is more common in HIV than TB

Tuberculosis, post-primary. There are large cavities in both apices and smaller cavities scattered throughout the lungs. The lungs are over-aerated and there is already scarring present. Dilated bronchi (tuberculous bronchiectasis) is present throughout the lungs.

Tuberculosis, cavitary. There is a cavity in the right upper lobe with an air-fluid level (black arrow). There is volume loss in the right upper lobe as evidenced by elevation of the minor fissure (white arrow).