A swollen epiglottis and aryepiglottic folds threaten the airway; the lateral neck radiograph shows the thumb sign, but a patient in distress goes to a secured airway first — imaging must never delay it.
Orient first
- Now more common in adults than children since Hib vaccination; the whole supraglottis swells, not only the epiglottis.
- The normal epiglottis is a thin curved leaf; thickening turns it into a thumb, and the aryepiglottic folds thicken too.
- Distinguish croup (subglottic narrowing, steeple sign on the frontal view) and retropharyngeal abscess (prevertebral soft-tissue widening).
Acquire the study
- Lateral soft-tissue neck radiograph, upright, neck extended, during inspiration.
The manoeuvre
- Epiglottis: thumb-shaped swelling in the lateral view; the vallecula is effaced (vallecula sign lost).
- Aryepiglottic folds: thickened, convex.
- Prevertebral soft tissue at C2 (≤ 7 mm in adults — verify) to separate a retropharyngeal process.
- Hypopharynx: ballooned by air proximal to the obstruction.
What confirms it
- Thickened epiglottis and aryepiglottic folds with a compatible acute history.
What licenses you to exclude it
- A thin, leaf-like epiglottis with a clear vallecula on a true lateral view makes epiglottitis unlikely; direct laryngoscopy is the reference test.
The classic misread
- An oblique film makes a normal epiglottis look thick — check that the mandibular rami superimpose.