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Right lung (inferior lobe)

The right inferior lobe of the lung is the largest lobe of the right lung, lying posteriorly and inferiorly, separated from the middle and superior lobes by the oblique fissure. It extends from the oblique fissure down to the diaphragm, occupying most of the posterior thoracic cavity. The inferior lobe is composed of five bronchopulmonary segments:

  • Superior (apical) segment (S6)

  • Medial basal segment (S7)

  • Anterior basal segment (S8)

  • Lateral basal segment (S9)

  • Posterior basal segment (S10)

This lobe plays a crucial role in gas exchange, particularly in the dependent regions of the lung, which are most affected by gravity in ventilation and perfusion. It is clinically important in diseases such as aspiration pneumonia, pulmonary embolism, and lower lobe lung carcinoma.

Synonyms

  • Right lower lobe of lung

  • Inferior lobe of right lung

  • Right pulmonary lower lobe

Function

  • Provides ventilation and gas exchange in the posterior and inferior thoracic cavity

  • Plays a key role in oxygenation due to its large surface area

  • Dependent portions are prone to aspiration, atelectasis, and infection

  • Segmental division allows surgical resections (lobectomy, segmentectomy) while preserving lung function

CT Appearance

Lung Window:

  • The right inferior lobe appears as the posteroinferior portion of the right lung, extending from the oblique fissure to the diaphragm

  • Normally shows fine vascular and bronchial markings

  • Pathology: consolidation (pneumonia), ground-glass opacities (infection, edema), atelectasis (volume loss with fissural shift), or nodules (metastasis, carcinoma)

  • Dependent regions often show gravity-related increased attenuation in supine scans

Mediastinal Window:

  • Useful for evaluating masses, consolidation, lymphadenopathy, or pleural effusion adjacent to the inferior lobe

  • The bronchovascular structures of the inferior lobe can be assessed relative to the hilum

  • Helps differentiate between lung lesions and mediastinal or pleural processes

Contrast-enhanced CT (CECT):

  • Enhances pulmonary vessels, improves characterization of masses, vascular lesions, or embolic disease

  • HRCT provides excellent evaluation of interstitial lung disease, fibrosis, and bronchiectasis

MRI Appearance

T1-weighted images:

  • Air-filled parenchyma of the inferior lobe appears as a signal void (black)

  • Vessels and bronchial walls appear as hypointense linear structures

  • Masses or consolidation appear as intermediate signal intensity relative to muscle

T2-weighted images:

  • Normal parenchyma: largely signal void (air)

  • Fluid, edema, consolidation, or masses appear hyperintense

  • Excellent for detecting pneumonia, pleural effusions, or tumors

T1 Post-Contrast (Gadolinium-enhanced):

  • Consolidation, tumors, or inflammatory lesions show contrast enhancement

  • Useful for differentiating infective consolidation (homogeneous enhancement) vs. malignancy (heterogeneous, nodular enhancement)

  • Pleural-based lesions or effusions show enhancement of pleural surfaces if inflamed or malignant

CT images

Right lung (inferior lobe) anatomy CT coronal image -img-00000-00000