Pulmonary tuberculosis is commonly divided into:
1) Primary (children and immunocompromised patients, 23%–34% of adult cases [4]) which may present with:
- Consolidations
- Lymphadenopathy
- Pleural effusion
- Miliary spread
2) Post-primary (adolescence and adulthood[4]) which may present with:
- Consolidations
- Cavitations
- Pleural effusion
- Centrilobular nodules
Tuberculosis can manifest as an active or inactive form (Fig.1).
Active forms can occur as primary or post-primary tuberculosis, while the latent form refers to the asymptomatic primitive infection.
Tuberculosis can lead to sequelae that can be seen on CXR.
Stability of radiographic findings for 6 months distinguishes inactive from active disease [5].
Main findings on CXR:
Consolidations:
- Areas of opacity in a segmental or lobar distribution
- Primary tuberculosis [4;7] (Fig.2):
- Dense, homogeneous
- Usually in middle lobe, lower lobes, or anterior segment of the upper lobes
- Unilateral
- Post-primary tuberculosis [4-6] (Fig.3; 4; 9 and 10)
- Patchy, heterogeneous, ill-defined, segmental
- Usually in the apical or posterior segment of the upper lobes or the superior segment of the lower lobes
- Two or more segments usually involved
- Bilateral
- Often indistinguishable from bacterial pneumonia. Lymphadenopathy and lack of response to conventional antibiotics suggest tuberculosis infection [3]
- Resolution is slow (even 2 years)
- Sequelae [3;5-8]:
- Fibronodular opacities: on apices or upper lung zones;
- Ghon focus: radiologic scar that can calcify. It is present in up to one-third of patients (Fig.4 and 5);
- Tuberculoma: sharply marginated round or oval lesions seen in both primary and post-primary tuberculosis, measuring 0.5–4.0 cm. The majority remains stable and calcify. Cavitation in 10‑50% of cases; satellite nodules in 80%. (Fig.6 and 12)
Lymphadenopathy:
- Usually mediastinal and hilar (Fig.2 and 3)
- It is the most common radiologic manifestation of primary tuberculosis
- Its prevalence decreases with age [6, 8-9]
- Usually unilateral; bilateral in 31% of cases [3, 8] (Fig.3 and 10)
- Nodes >2 cm in diameter are highly suggestive [3]
- It can be the sole radiographic feature in primary infection[3]
- Sequelae:
- Calcified normal-sized lymph nodes: > 6 months after the initial infection. With treatment, there is a slower resolution of the lymphadenopathy compared to the parenchymal disease, so nodal calcification may develop [3] (Fig.5 and 7).
- Ranke complex: the combination of calcified hilar nodes and a Ghon focus [3;9] (Fig.5 and 8).
Pleural effusion:
- 25%-38% of primary tuberculosis cases [5;8]; 18% of post-primary tuberculosis[3;5]
- Increasing prevalence with age [9]
- Primary tuberculosis (Fig.2) [3,6,8]
- Unilateral, large
- Not loculated
- On the same side as the primary focus
- +/- evidence of parenchymal disease on CXR
- 3–7 months after initial exposure
- Post-primary tuberculosis (Fig.10) [3, 4-6]
- Small
- Loculated
- + parenchymal disease
- Rarely the sole imaging manifestation
- Can remain stable for many years
- Complications [3-5]:
- Tuberculous empyema: loculated pleural fluid collection with parenchymal disease and cavitation, associated with pleural thickening (Fig.11)
- Bronchopleural fistula: air-fluid level within an empyema.
- Empyema necessitates: untreated empyema extends into the chest wall
- Bone erosion
- Sequelae [5]:
- Residual pleural thickening and calcification (Fig.7 and 13)
Cavitations:
- Hallmark of post-primary tuberculosis (about 50% of patients)[3], it can occur in a minority of primary tuberculosis (29%) [5]
- Usually multiple (Fig.3; 4; 9 and 10) within areas of consolidation[3-5]
- Complications:
- Superinfections: air-fluid levels inside cavities (Fig.5)
- Pneumothorax: 5% of patients [3] (Fig.10)
- Lobar or complete lung opacification and destruction, if untreated (Fig.10)
- Endobronchial spread: caseous necrosis of bronchial walls with airway communication [3-5;9]
- Sequelae:
- Emphysematous changes
- Fibrosis/scarring (Fig.12)
- Persistence of cavities: predisposition to bacterial superinfection and mycetoma formation (air crescent sign).
- After healing: upper lobe volume loss (especially apical), atelectasis, architectural distortion or traction bronchiectasis (Fig.6 and 12)
- Interstitial fibrosis [3-6] (Fig.14)
Miliary Tuberculosis:
- Hematogenous seeding of TB
- Acute, severe illness with high mortality [5;10]
- 1-7% of patients with all forms of tuberculosis.
- Evenly distributed diffuse 2–3-mm nodules, in both lungs, with a slight lower lobe predominance [3-6;10] (Fig.15; 16 and 17)
- Thickening of inter- and intra-lobular septa[6]
- CXR allows diagnosis in 59-69% of cases[10].
- Early in the course of the disease, CXR may be normal in 25‑40% of cases[8].
- Nodules usually resolve within 2– 6 months with treatment, without scarring or calcification; however, they may coalesce with a “snow‑storm” appearance[3;8].
- Complications:
- Acute respiratory distress syndrome [6]
- Distribution of tuberculosis in other organs
- Pneumothorax (rare) (Fig.17)