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Right anterior segmental bronchus (B3)

The right anterior segmental bronchus (B3) is one of the three major segmental branches of the right superior lobar bronchus, along with the apical (B1) and posterior (B2) bronchi. It arises from the anterior aspect of the superior lobar bronchus and courses forward and downward to supply the anterior segment of the right upper lobe. This bronchus ventilates the anterior portion of the lobe, adjacent to the sternum and anterior chest wall. The B3 bronchus is a key anatomical landmark in bronchoscopy, thoracic imaging, and pulmonary segmentectomy.

Synonyms

  • B3 bronchus

  • Right anterior bronchus

  • Anterior segmental bronchus of right upper lobe

Function

  • Conducts air to the anterior segment of the right upper lobe

  • Maintains efficient ventilation and gas exchange in the anterior thoracic region of the lung

  • Assists in mucus clearance from the anterior segment

  • Serves as an important surgical and radiological landmark for resection planning and disease localization

CT Appearance

Lung Window:

  • Appears as an air-filled hypodense (black) tubular structure branching forward from the right superior lobar bronchus toward the anterior lung field

  • Normally has thin, inconspicuous walls

  • Pathology: wall thickening (bronchitis), obstruction by mucus, tumor, or foreign body, and tree-in-bud nodules (infection or inflammation)

Mediastinal Window:

  • Shows B3 as a thin-walled soft tissue structure within the anterior right upper lobe

  • Highlights adjacent vascular structures and mediastinum

  • Useful for distinguishing endobronchial lesions vs. extrinsic compression (lymphadenopathy, masses)

Contrast-enhanced CT (CECT):

  • Enhances bronchial wall and adjacent vessels

  • Defines endobronchial tumors, peribronchial spread of carcinoma, vascular compression, or stenosis

  • HRCT provides detailed assessment of lumen caliber, branching anatomy, and subtle disease

MRI Appearance

T1-weighted images:

  • Air in the lumen appears as a signal void (black)

  • Bronchial wall shows low signal intensity, with surrounding mediastinal fat hyperintense for contrast

  • Wall thickening or nodules appear hypointense relative to lung parenchyma

T2-weighted images:

  • Normal air-filled lumen remains a signal void

  • Fluid, mucus, or inflammatory material in the lumen is bright hyperintense

  • Thickened or inflamed bronchial wall shows intermediate to hyperintense signal

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal bronchial wall enhances as a thin rim

  • Pathology (e.g., tumor, granuloma, infection) shows thick, irregular, heterogeneous enhancement, sometimes with endobronchial nodularity

CT images

Right anterior segmental bronchus (B3) anatomy CT coronal image -img-00000-00000

CT images

Right anterior segmental bronchus (B3) anatomy CT coronal image -img-00000-00000_00001