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Signet ring sign

ChestCT / HRCT

A dilated bronchus seen in cross-section sits adjacent to its smaller accompanying pulmonary artery, the paired ring-and-dot resembling a signet ring.

What it means

Bronchial dilatation with a broncho-arterial ratio greater than 1, the defining feature of bronchiectasis.

Mechanism

Chronic airway inflammation and wall destruction dilate the bronchus so its calibre exceeds that of the adjacent artery, which normally matches it.

Associated conditions

  • Bronchiectasis
  • Cystic fibrosis
  • Allergic bronchopulmonary aspergillosis
  • Prior severe infection

Pearls

  • A broncho-arterial ratio above 1 is the key quantitative sign of bronchiectasis.
  • Look on the same slice for lack of airway tapering and visible airways within 1 cm of the pleura.

References

  • Radiopaedia: Signet ring sign (bronchiectasis)

For educational use only. This dictionary is a study aid and reference, not a diagnostic tool, and must not be used to guide clinical decisions or patient care. Imaging appearances vary; always correlate with the full clinical picture and confirm with a qualified radiologist.