Tuberculosis types with xray and findings

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Tuberculosis: Types, X-ray Findings & Radiological Features

Overview - Natural History

Natural history and spectrum of tuberculosis - from primary complex through latent, secondary, miliary TB

The natural history of TB - Primary Complex → Progressive Primary TB / Latent Lesions → Secondary (Reactivation) TB / Miliary TB (from Robbins & Kumar Basic Pathology)

1. Primary Tuberculosis

Definition: Results from the initial infection with Mycobacterium tuberculosis in a host with no prior immunity.

Pathology

The inhaled bacilli settle in the mid/lower lung zones and form the Ghon focus (area of consolidation).
Draining lymphatics carry bacilli to the ipsilateral hilar nodes → together these form the Ghon complex (primary complex).
In most immunocompetent individuals, the infection is controlled; the lesions undergo caseous necrosis, calcification, and scarring.
If immunity fails to contain it → Progressive Primary TB (see below).

Chest X-ray Findings

Middle or lower lung zone opacity/consolidation (unlike reactivation TB, which is upper lobe)
Ipsilateral hilar/paratracheal lymphadenopathy - this is the most characteristic feature
Possible pleural effusion
Possible atelectasis from lymph node compression of airways

Primary tuberculosis - right lower lobe consolidation with right hilar and paratracheal lymphadenopathy (arrows)

Figure 53.1 - Primary TB: Right lower lobe consolidation + right hilar lymphadenopathy (arrow) + right paratracheal lymph node enlargement (arrowhead). (Murray & Nadel's Respiratory Medicine)

From Grainger & Allison (shown below), primary TB in a child with hilar adenopathy:

Primary TB - chest X-ray (A) and coronal CT (B) showing hilar adenopathy

Fig. 70.28 Primary Tuberculosis - CXR (A) and coronal CT (B) demonstrating hilar adenopathy. (Grainger & Allison's Diagnostic Radiology)

2. Progressive Primary Tuberculosis

Definition: Primary infection that fails to be contained by developing cell-mediated immunity. More common in children, the elderly, and immunosuppressed.

X-ray Findings

Rapidly enlarging pulmonary consolidation (lobar pattern)
Cavitation can form in the primary focus
Prominent hilar/mediastinal adenopathy
May be indistinguishable from acute bacterial lobar pneumonia

3. Secondary (Reactivation) Tuberculosis

Definition: Develops when a previously infected individual undergoes reactivation of latent TB - either spontaneously (due to waning immunity) or through reinfection. This is the most common form in adults.

Pathology

Reactivation driven by falling cell-mediated immunity (HIV, malnutrition, steroids, DM, old age, TNF inhibitors)
Localizes to the lung apices because of higher oxygen tension there
Hallmark: caseous necrosis with cavity formation
Bronchogenic spread can carry infected material to other parts of the lung

Chest X-ray Findings

Upper lobe involvement - predominantly apical and posterior segments of the right upper lobe (most common site), also apical-posterior segment of the left upper lobe
Cavitation - thick-walled cavities, often in the upper lobes (highly characteristic)
Fibronodular or patchy consolidation
Volume loss and fibrosis with superior hilar retraction (old healed disease)
Calcifications in healed lesions (Ranke complex)
Bronchogenic spread pattern: new acinar/nodular opacities ("tree-in-bud") in ipsilateral lower lobe or contralateral lung
Absence of hilar adenopathy (in contrast to primary TB)

Cavitary tuberculosis - extensive right upper lobe cavitation

Figure 53.2 - Cavitary (Reactivation) TB: Extensive right upper lobe cavitation. (Murray & Nadel's Respiratory Medicine)

4. Miliary Tuberculosis

Definition: Results from massive hematogenous dissemination of M. tuberculosis - can occur as a complication of either primary or reactivation TB. The term "miliary" comes from the radiographic appearance resembling millet seeds (1-5 mm each).

At-risk groups

Children, elderly, immunocompromised (HIV, organ transplant, corticosteroids). Mortality rate is 20-30%.

Chest X-ray Findings

Diffuse, bilateral, uniformly distributed tiny nodules (1-3 mm) throughout both lung fields
Nodules are randomly distributed - no zone predilection
"Snow-storm" or "millet seed" appearance
May be subtle early on; CT is far more sensitive

Miliary tuberculosis - bilateral, randomly distributed small nodules throughout both lung fields

Figure 53.3 - Miliary TB: Numerous small, randomly distributed bilateral nodules ("miliary pattern"). (Murray & Nadel's Respiratory Medicine)

5. Tuberculosis in HIV/Immunocompromised Patients

The radiographic pattern depends on the degree of CD4 depletion:

CD4 count	Pattern
Early HIV (CD4 relatively preserved)	Typical pattern - upper lobe infiltrates, cavitation
Advanced HIV (low CD4 / AIDS)	Atypical pattern - lower zone or diffuse opacities, prominent hilar/mediastinal adenopathy, NO cavitation
Some HIV patients	Normal chest radiograph despite active TB

X-ray Findings (Advanced HIV)

Bilateral hilar lymphadenopathy (prominent, unlike immunocompetent reactivation)
Diffuse nodular or consolidative opacities
Lower lung zone involvement
Cavitation uncommon
Pleural effusion more frequent

TB in HIV patient - bilateral hilar adenopathy with nodular parenchymal opacities (arrows/arrowheads)

Figure 53.4 - TB + HIV: Bilateral hilar lymph node enlargement (arrows) + nodular opacities (arrowheads) + nodular consolidation (double arrowheads). (Murray & Nadel's Respiratory Medicine)

Summary Table

Type	Location on CXR	Key Feature	Adenopathy	Cavitation
Primary TB	Mid/lower zones	Consolidation + hilar LN	Yes (ipsilateral)	Rare
Progressive Primary	Any zone, lobar	Rapid consolidation	Yes	Sometimes
Latent TB	Normal	No active lesion	No	No
Reactivation (Secondary) TB	Upper lobes (apical/posterior)	Cavitary fibronodular	Absent	Common
Miliary TB	Diffuse bilateral	1-3 mm nodules ("millet seeds")	Variable	No
TB + HIV	Lower zones / diffuse	Atypical infiltrates	Yes (bilateral)	Uncommon

Additional Radiological Notes

Ranke complex: Calcified primary focus (Ghon focus) + calcified hilar lymph node = healed primary TB
Simon foci: Small calcified apical nodules representing early hematogenous seeding - can reactivate years later
CT advantages: Sensitivity 96% vs 48% for plain CXR in active TB. CT better detects lymphadenopathy, "tree-in-bud" pattern (bronchogenic spread), and cavity walls.
"Tree-in-bud" sign on CT: Centrilobular nodules connected by branching linear densities - highly suggestive of endobronchial spread of TB.
Activity cannot be determined from a single CXR alone - a cavity may be a sterile old lesion, and a fibrotic-appearing area may be active.

Sources: Murray & Nadel's Textbook of Respiratory Medicine, Grainger & Allison's Diagnostic Radiology, Robbins & Kumar Basic Pathology, Goldman-Cecil Medicine, Tintinalli's Emergency Medicine

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