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Inferior lobe of left lung

The inferior lobe of the left lung (left lower lobe) is the larger and more posterior of the two lobes of the left lung. It occupies the posteroinferior portion of the left hemithorax and plays a major role in gas exchange due to its large volume and dependent position.

It is an important anatomical region in thoracic imaging, pulmonary medicine, and surgery, frequently evaluated on chest radiographs, CT, and MRI.

Synonyms

  • Left lower lobe

  • Inferior lobe of left lung

Location

  • Located in the posteroinferior part of the left lung

  • Inferior to the oblique fissure

  • Posterior to the superior lobe of the left lung

  • Extends from the oblique fissure to the diaphragm

  • Occupies a large portion of the posterior thoracic cavity

  • In close proximity to the left hemidiaphragm

Anatomical components

  • Bronchus:

    • Left inferior lobar bronchus arising from the left main bronchus

  • Segments (bronchopulmonary segments):

    • Superior segment (S6)

    • Anteromedial basal segment (S7 + S8, often combined)

    • Lateral basal segment (S9)

    • Posterior basal segment (S10)

  • Vascular supply:

    • Branches of the left pulmonary artery

    • Pulmonary veins draining to the left inferior pulmonary vein

Relations

Superiorly:

  • Oblique fissure

  • Superior lobe of the left lung

Inferiorly:

  • Left hemidiaphragm

Anteriorly:

  • Heart and pericardium (partially)

Posteriorly:

  • Posterior thoracic wall

  • Lower thoracic vertebrae

Medially:

  • Mediastinum

  • Descending thoracic aorta

  • Esophagus (posteromedial proximity)

Laterally:

  • Costal pleura and ribs

Bronchopulmonary segment orientation

  • Superior segment (S6): Posterior and superior

  • Basal segments (S7–S10): Inferior and peripheral, closely related to the diaphragm

  • Dependent positioning: Predisposes this lobe to gravity-related processes

X-ray appearance

Chest radiograph (PA and lateral views):

  • PA view:

    • Inferior lobe largely obscured by the heart and diaphragm

    • Loss of left hemidiaphragm outline may suggest involvement

  • Lateral view:

    • Triangular opacity posteriorly and inferiorly

    • Clear visualization behind the cardiac silhouette

CT appearance

Lung window:

  • Parenchyma: Normal aerated lung with fine bronchovascular markings

  • Bronchi: Tapering air-filled bronchi extending to the periphery

  • Pulmonary vessels: Well-defined branching arteries and veins

  • Fissure: Oblique fissure visible as a thin curvilinear line

  • Diaphragmatic interface: Smooth, well-defined basal margin

MRI appearance

T1-weighted images:

  • Normal lung parenchyma: Low signal intensity due to air content

  • Pulmonary vessels: Intermediate signal

  • Bronchial walls: Intermediate signal with low-signal air-filled lumen

T2-weighted images:

  • Lung parenchyma: Low signal intensity

  • Pulmonary vessels: Relatively higher signal than surrounding lung

  • Bronchial structures: Intermediate signal walls

STIR:

  • Lung parenchyma: Suppressed low signal

  • Vessels and soft tissues: Relatively hyperintense

CT image

Inferior lobe of left lung CT anatomy image -img-00000-00000

CT image

Inferior lobe of left lung CT Anatomy, Location and Imaging Appearance CT anatomy image -img-00000-00000

X-Ray image

Inferior lobe of left lung X RAY anatomy image -img-00000-00000