Does a multinodular goiter (MNG) compressing the trachea on ultrasound require a Magnetic Resonance Imaging (MRI) for further evaluation?

Imaging for Multinodular Goiter with Tracheal Compression

For a multinodular goiter (MNG) compressing the trachea on ultrasound, CT scan is preferred over MRI for further evaluation due to less respiratory motion artifact and better assessment of tracheal compression. 1

Initial Assessment of Multinodular Goiter

• Ultrasound is the appropriate first-line imaging modality for suspected goiter, confirming thyroid origin and characterizing goiter morphology 1, 2
• Ultrasound can identify nodules requiring biopsy based on suspicious features but has limitations in fully evaluating tracheal compression 1, 2
• Tracheal compression due to goiters can lead to significant respiratory symptoms including dyspnea, orthopnea, obstructive sleep apnea, and stridor 3

Recommended Imaging for Tracheal Compression

• CT scan is superior to ultrasound for:

  • Evaluating the degree of tracheal compression 1
  • Assessing substernal extension of the goiter 1, 3
  • Evaluating deep extension to the retropharyngeal space 1
  • Planning surgical approach when compression symptoms are present 1

• CT without IV contrast is usually sufficient for goiter evaluation unless there is concern for infiltrative neoplasm 1, 2

Why CT is Preferred Over MRI

• CT is preferred over MRI because there is less respiratory motion artifact 1, 2
• CT more effectively defines the degree of tracheal compression compared to ultrasound 1, 3
• CT provides valuable information for surgical planning when compression symptoms are present 1, 3

Clinical Implications of Tracheal Compression

• Tracheal compression can be a serious complication of multinodular goiter, potentially leading to acute airway obstruction in severe cases 4, 5
• Narrowing of the trachea can lead to development of hypertension in the pulmonary circulation 5
• Tracheal compression may be present even in asymptomatic patients, with significant tracheal deviation found on imaging 6
• When trachea is narrowed to 10 mm or less, patients may develop "wheezing" on inhalation/exhalation with statistically significant prevalence of pulmonary hypertension 5

Management Considerations

• Patients with compression symptoms due to an enlarged thyroid gland are usually candidates for surgery 7
• Surgical treatment is considered standard therapy for nontoxic goiter with compression symptoms 8
• The surgeon should identify the recurrent laryngeal nerve during thyroidectomy to optimize voice outcomes and reduce risk of injury 1
• Removal of a large goiter may cause collapse of an already tracheomalacic airway, requiring careful perioperative management 1

Important Caveats

• A large, long-standing goiter may cause tracheal deviation that can complicate intubation during surgery 1
• Early surgical intervention should be considered when there is radiographic evidence of tracheal deviation, as complete airway occlusion may occur suddenly and unpredictably once symptoms develop 6
• Compression symptoms may be masked by cardiopulmonary syndromes, leading to delayed diagnosis and treatment 5
• Peak inspiratory flow rates should be measured via spirometry in all goiters to assess the degree of tracheal compression 4