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Topic

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Carina of trachea

The carina of the trachea is the ridge of cartilage and mucosa located at the inferior end of the trachea where it bifurcates into the right and left main bronchi. It is formed by the downward and backward projection of the last tracheal cartilage ring. The carina is located at the level of the sternal angle (T4–T5 intervertebral disc) in adults, though its level may vary with respiration and body habitus.

The carina is an essential airway landmark during bronchoscopy and imaging, and its widening, blunting, or distortion is often associated with pathology such as left atrial enlargement, subcarinal lymphadenopathy, or mediastinal masses. It is also highly sensitive: stimulation during bronchoscopy induces violent coughing.

Synonyms

  • Tracheal carina

  • Tracheal bifurcation

  • Carinal ridge

Function

  • Marks the division of the trachea into the right and left main bronchi

  • Maintains structural integrity at the bifurcation through cartilaginous support

  • Provides a protective reflex zone for cough initiation

  • Serves as a critical anatomical landmark in bronchoscopy, thoracic surgery, and imaging

MRI Appearance

T1-weighted images:

  • Appears as a hypointense cartilaginous ridge separating the signal voids of the right and left bronchi

  • Adjacent mediastinal fat provides natural contrast

T2-weighted images:

  • Cartilage shows low-to-intermediate signal

  • Surrounding airway lumen is a signal void (air-filled)

  • Peribronchial pathology (e.g., lymphadenopathy, masses) appears hyperintense

T2 TRUFISP (cardiac/respiratory-gated):

  • Clearly demonstrates the dynamic airway lumen and bifurcation during respiratory motion

  • Useful for functional airway assessment and stenosis detection

STIR (Short Tau Inversion Recovery):

  • Suppresses mediastinal fat, improving contrast of peribronchial tissues

  • Highlights inflammatory or edematous changes around the carina

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Carinal cartilage itself does not enhance significantly

  • Surrounding soft tissue pathology (tumors, lymphadenopathy, infection) enhances, delineating carinal involvement

MRI Non-Contrast 3D Cardiac/Respiratory-Gated Imaging:

  • Provides 3D airway reconstructions, clearly showing the tracheal bifurcation

  • Useful for surgical planning and congenital airway anomaly evaluation without contrast

CT Appearance

CT Chest (Contrast-enhanced):

  • Gold standard for carina evaluation

  • Air-filled trachea and bronchi appear hypodense, separated by the sharp carinal ridge

  • Detects carinal widening (>100°), blunting, or displacement due to left atrial enlargement, mediastinal masses, or subcarinal lymphadenopathy

  • Multiplanar and 3D reconstructions provide excellent depiction for bronchoscopic correlation

CT images

Carina of trachea anatomy CT axial image -img-00000-00000

CT images

Carina of trachea anatomy CT coronal image -img-00000-00000

MRI images

Carina of trachea anatomy MRI coronal image -img-00000-00000