Preliminary Diagnosis: Pulmonary Tuberculosis

I. What imaging technique is first-line for this diagnosis?

Chest radiograph (CXR) with posteroanterior (PA) and lateral views.

II. Describe the advantages and disadvantages of this technique for diagnosing pulmonary tuberculosis.

Advantages

  • Can be diagnostic of primary and post-primary tuberculosis (TB).

  • Often adequate to show the various findings of post-primary TB, including cavitation, apical distortion, and miliary disease.

  • Usually adequate to monitor response to treatment.

  • Widely available and inexpensive.

Disadvantages

  • Pulmonary findings of TB on CXR are often non-specific, requiring further imaging and tests for diagnosis.

  • Less sensitive than CT for signs of active pulmonary TB.

  • Exposes the patient to ionizing radiation.

III. What are the contraindications for the first-line imaging technique?

Chest radiography has no significant contraindication. Some institutions may require consent for pregnant patients.

IV. What alternative imaging techniques are available?

  • Computed tomography (CT) chest with contrast

  • CT chest without contrast

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing pulmonary tuberculosis.

CT chest with contrast
Advantages

  • Optimal study for the evaluation and diagnosis of primary or post-primary TB

  • Shows the pulmonary parenchymal and mediastinal manifestations of primary and post-primary TB

  • Optimal examination for the diagnosis of many pulmonary diseases, including malignancy and infection

Disadvantages

  • Exposes the patient to more ionizing radiation than chest radiography.

  • The contrast dose administered may have to be reduced or withheld if the patient has decreased renal function.

  • Patients with known allergic reaction to iodinated contrast must undergo pre-treatment with steroids and anti-histamines for at least 13 hours prior to contrast dose, or have the contrast withheld.

CT chest without contrast
Advantages

  • More sensitive than CXR for the pulmonary parenchymal disease of TB.

  • Can be safely used in patients with renal disease or contrast allergy.

Disadvantages

  • Poorly evaluates the mediastinal and chest wall manifestations of pulmonary TB, including lymphadenopathy.

  • Exposes the patient to more ionizing radiation than chest radiography.

VI. What are the contraindications for the alternative imaging techniques?

CT chest with contrast

  • May be contraindicated in pregnant patients.

  • Relative contraindication in patients with renal failure.

  • Relative contraindication in patients with contrast allergy.

CT chest without contrast

  • Contraindicated in pregnant women, especially during the first and second trimesters.

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