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Posterior basal segmental bronchus of left lung (B10)

The posterior basal segmental bronchus (B10) is the most posterior and inferior segmental branch of the left lower lobar bronchus. It arises from the common basal bronchus and courses posteriorly and inferiorly toward the posterior basal segment of the left lower lobe, which lies adjacent to the diaphragm and posterior thoracic wall. This segment contributes significantly to the functional capacity of the lower lobe and is a common site of pathology such as aspiration pneumonia, atelectasis, and metastatic disease, due to its dependent position.

Synonyms

  • B10 bronchus (left lung)

  • Posterior basal bronchus

  • Dorsal basal segmental bronchus

Function

  • Conducts air to the posterior basal segment of the left lower lobe

  • Plays a role in ventilation and gas exchange in the dependent lung regions

  • Important in mucus clearance; due to gravity dependence, it is prone to fluid or secretion accumulation

  • Serves as a surgical and radiological landmark in segmentectomy, lobectomy, and bronchoscopic procedures

CT Appearance

Lung Window:

  • Appears as an air-filled tubular structure branching posteriorly and inferiorly from the common basal bronchus of the left lower lobe

  • Normally thin-walled and sharply outlined against aerated lung

  • Pathology: wall thickening (bronchitis), mucus plugging, atelectasis, or opacities from aspiration and infection

Mediastinal Window:

  • Bronchial wall is visible as a thin soft-tissue rim

  • Enhances appreciation of relationships to adjacent vessels, diaphragm, and posterior thoracic wall

  • Differentiates endobronchial lesions from peribronchial masses or extrinsic compression

Contrast-enhanced CT (CECT):

  • Enhances the bronchial wall and nearby vascular structures

  • Useful for detecting endobronchial tumors, peribronchial nodal disease, or compression by pleural effusion/masses

  • HRCT provides fine detail of airway caliber, wall thickness, and segmental anatomy

MRI Appearance

T1-weighted images:

  • Air-filled lumen appears as a signal void (black)

  • Bronchial wall is low signal, with surrounding peribronchial fat hyperintense, aiding visibility

T2-weighted images:

  • Lumen remains a signal void when air-filled

  • If fluid, secretions, or inflammatory exudate are present, the lumen appears bright hyperintense

  • Wall thickening or inflammation appears as intermediate to high signal intensity

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal bronchial wall shows thin, mild rim enhancement

  • Pathology such as tumor, granuloma, or infection appears as irregular thickened enhancing walls or nodular endobronchial lesions

CT images

Posterior basal segmental bronchus of left lung (B10) anatomy CT coronal image -img-00000-00000