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Topic

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Left Lung (Superior Lobe)

The superior lobe of the left lung forms the upper portion of the left lung and extends from the apex (above the first rib and clavicle) down to the oblique fissure. It consists of apical, posterior, anterior, superior lingular, and inferior lingular bronchopulmonary segments, making it larger and more complex than the right upper lobe. The lingula, a tongue-shaped projection, is unique to the left lung and functionally analogous to the right middle lobe. The superior lobe lies adjacent to the heart, aortic arch, subclavian vessels, and esophagus, making it critical in thoracic radiology and surgery.

Synonyms

  • Upper lobe of the left lung

  • Left upper lobe (LUL)

  • Lingular lobe (for lingular portion)

Function

  • Provides ventilation and gas exchange for the upper half of the left lung

  • Maintains oxygenation in five distinct bronchopulmonary segments

  • Supports respiratory mechanics by expanding superiorly and laterally during inspiration

  • Lingula helps compensate functionally for the absence of a true right middle lobe

CT Appearance

Lung Window:

  • The superior lobe appears as an aerated region of lung parenchyma above the oblique fissure

  • Normal appearance: homogeneous low attenuation (black, air-filled parenchyma) with visible fine bronchovascular markings

  • Pathology:

    • Consolidation or pneumonia = high-attenuation patchy or lobar opacities

    • Atelectasis = volume loss with fissure displacement

    • Nodules or masses = focal soft tissue opacities

    • Ground-glass opacities = hazy increased attenuation

Mediastinal Window:

  • Fissures may be seen as thin soft tissue lines separating lobes

  • Provides better visualization of adjacent mediastinal structures (aorta, pulmonary arteries, lymph nodes)

  • Helps differentiate intrapulmonary from mediastinal pathology

Contrast-enhanced CT (CECT):

  • Enhances pulmonary vasculature for detailed assessment of arterial and venous supply

  • Useful for identifying tumors, lymphadenopathy, vascular compression, and pleural disease

  • HRCT demonstrates segmental anatomy and interstitial lung changes

MRI Appearance

T1-weighted images:

  • Aerated lung parenchyma shows signal void (black) due to low proton density

  • Bronchovascular structures show low to intermediate signal

  • Adjacent fat and mediastinal structures provide contrast

T2-weighted images:

  • Aerated lung remains a signal void

  • Fluid-filled or consolidated areas appear bright hyperintense

  • Useful for detecting edema, pneumonia, or mass lesions

T1 Post-Contrast (Gadolinium-enhanced):

  • Enhances pulmonary vessels and pathological tissue

  • Tumors and inflammatory lesions show heterogeneous enhancement, while normal parenchyma remains signal void

  • Helpful for assessing tumor vascularity and pleural invasion

CT image

Left lung (superior lobe) anatomy CT coronal image -img-00000-00000