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ChestDemonstration data

CT Chest: Tuberculosis Assessment

CT of the chest provides high-resolution assessment of tuberculosis when the radiograph is inconclusive or complications are suspected. It characterizes activity through tree-in-bud and centrilobular nodularity, defines cavities and bronchiectasis, and detects necrotic lymphadenopathy, empyema, and vascular or pericardial involvement. CT is especially valuable in complex disease, drug-resistant TB, HIV coinfection, and treatment monitoring.

Indications

  • Inconclusive or discordant chest radiograph with clinical suspicion of TB
  • Complex or multidrug-resistant TB requiring detailed disease mapping
  • HIV-TB coinfection with atypical presentations
  • Suspected complications: empyema, bronchopleural fistula, hemoptysis source, mycetoma
  • Assessment of mediastinal and hilar lymphadenopathy with necrotic centers
  • Treatment monitoring and evaluation of paradoxical reactions
  • Suspected pericardial or vascular involvement
  • Differentiation of active from inactive disease and detection of sequelae

Contraindications & Cautions

  • Radiation dose; use low-dose protocols particularly for follow-up and in younger patients
  • Iodinated contrast cautions: prior severe reaction, and impaired renal function (check eGFR)
  • Pregnancy: perform only when clearly justified with dose optimization and shielding; weigh against alternatives
  • Contrast avoided or premedication considered in patients with significant allergy history
  • Apply ALARA and select non-contrast technique when vascular or nodal enhancement is not required

Patient Preparation

  • Confirm renal function and contrast allergy history when IV contrast is planned
  • Explain breath-hold instructions; supine positioning with arms raised
  • Fast for a few hours if contrast is planned per local protocol
  • Establish intravenous access for contrast administration
  • Maintain airborne infection-control precautions for infectious patients
  • Confirm and document pregnancy status in women of childbearing age

Technique & Parameters

  • Volumetric acquisition with thin sections (1-1.25 mm) and high-resolution reconstruction
  • Initial non-contrast series for parenchymal characterization
  • IV contrast (approximately 60-100 mL at 2-3 mL/s) when lymphadenopathy, pleural, pericardial, or vascular complications are suspected, imaged in the venous phase
  • Low-dose technique for follow-up imaging to limit cumulative dose
  • Expiratory or prone images to confirm air trapping or clarify dependent versus true disease
  • Multiplanar and maximum-intensity-projection reconstructions to depict tree-in-bud and nodular spread
  • Coverage from lung apices through the costophrenic angles and adrenal glands

Systematic Review

  • Distribution of nodular and tree-in-bud opacities indicating active endobronchial spread
  • Cavities: number, size, wall thickness, air-fluid levels, and satellite nodules
  • Consolidation and its segmental distribution
  • Bronchiectasis and airway narrowing
  • Lymph nodes: size, distribution, and central low attenuation with rim enhancement
  • Pleura: effusion, empyema, thickening, and bronchopleural fistula
  • Pericardium: effusion, thickening, and calcification
  • Vascular structures: Rasmussen aneurysm and mediastinal invasion; sequelae such as fibrosis and calcification

Key Findings & Significance

  • Centrilobular nodules and tree-in-bud opacities are the hallmark of active endobronchial TB spread
  • Thick-walled cavities with surrounding nodules indicate active cavitary disease and high bacillary load
  • Necrotic lymph nodes with low-attenuation centers and peripheral rim enhancement are highly suggestive of TB
  • Miliary pattern of diffuse randomly distributed micronodules indicates hematogenous dissemination
  • Empyema with split pleura sign and possible bronchopleural fistula indicates complicated pleural TB
  • Pericardial thickening and effusion indicate tuberculous pericarditis
  • Fibrosis, traction bronchiectasis, calcified nodes, and mycetoma within a cavity indicate chronic or healed disease

Differential Considerations

  • Tree-in-bud: active TB, nontuberculous mycobacteria, bacterial or viral bronchiolitis, aspiration
  • Cavitary disease: TB, necrotizing bacterial or fungal pneumonia, cavitating malignancy, granulomatosis with polyangiitis
  • Necrotic lymphadenopathy: TB, metastatic carcinoma, lymphoma, fungal infection, Whipple disease
  • Miliary nodules: miliary TB, fungal infection, hematogenous metastases, sarcoidosis, pneumoconiosis
  • Pleural collection: tuberculous empyema, parapneumonic effusion, malignant effusion
  • Chronic cavity with content: mycetoma (aspergilloma), TB, cavitating carcinoma

Pearls & Pitfalls

  • Tree-in-bud opacities are the most reliable CT sign of active infectious disease and imply infectivity
  • Rim-enhancing necrotic nodes strongly favor TB over reactive adenopathy in the correct clinical context
  • Use MIP reconstructions to detect subtle nodular and miliary patterns
  • A crescent of air within a cavity mass (air-crescent sign) suggests a mycetoma in a healed cavity
  • Paradoxical worsening on treatment, especially in HIV with immune reconstitution, can mimic treatment failure
  • Distinguish active disease from fibrotic sequelae to avoid over-treatment; correlate with microbiology
  • Screen for Rasmussen aneurysm as a cause of hemoptysis in cavitary disease

Structured Report

  • State protocol including contrast use and comparison with prior imaging
  • Describe parenchymal disease distribution, activity signs (tree-in-bud, nodules), and cavitation
  • Report lymphadenopathy with size, distribution, and necrosis or rim enhancement
  • Report pleural, pericardial, airway, and vascular complications
  • Comment on chronic sequelae and mycetoma
  • Assess interval change and treatment response
  • Impression: summarize likelihood of active TB, complications requiring intervention, and recommend microbiologic confirmation and clinical correlation

References

  • WHO Consolidated Guidelines on Tuberculosis and use of imaging in TB diagnosis and management
  • Fleischner Society Glossary of Terms for Thoracic Imaging (Hansell DM et al.)
  • Nachiappan AC et al. Pulmonary Tuberculosis: Role of Radiology in Diagnosis and Management, RadioGraphics
  • ATS/CDC/IDSA Official Practice Guidelines on Diagnosis of Tuberculosis

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.