LearningRadiology - TB, Tuberculosis, Reactivation

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

Bilateral upper lobe Tuberculous
cavitary pneumonia (worse on the left)

§ 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