Saber-sheath trachea
A saber-sheath trachea, also called scabbard trachea, is an abnormally shaped windpipe. It shows a narrower section inside the chest with a wider back part, giving the trachea a flattened, scabbard-like cross-section. The inner lining remains smooth, with no nodules or thickening.
The trachea is a cartilage-supported tube that carries air from the nose and mouth to the lungs. It usually measures about 8–13 cm in length, with part inside the chest (intra-thoracic) about 6–9 cm and part outside (extra-thoracic) about 2–4 cm. The trachea is kept open by C-shaped rings of cartilage to prevent collapse during breathing.
Normal tracheal diameters vary by sex. The side-to-side (coronal) width is roughly 13–25 mm in men and 10–21 mm in women. The front-to-back (sagittal) width is about 13–27 mm in men and 10–23 mm in women.
Saber-sheath trachea is often linked with chronic obstructive pulmonary disease (COPD) and can occur with long-term external compression, such as from a goitre. The exact cause is not fully understood, but COPD is a common association.
Diagnosis is usually made by calculating the tracheal index, which is the ratio of the trachea’s width to its depth on imaging. A normal index is around 1.0; a value below about 0.67 suggests saber-sheath trachea.
On CT scans, saber-sheath trachea may show inward curving of the tracheal sides and only mild thickening of the walls inside the chest. The cartilage rings can become stiffer and may ossify (harden into bone-like tissue) with age.
This page was last edited on 2 February 2026, at 08:53 (CET).