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Oblique fissure of right lung

The oblique fissure of the right lung is a major anatomical fissure that separates the right lower lobe from the right upper and middle lobes. It begins posteriorly at the level of the T4–T5 vertebrae, runs obliquely downward and forward across the lung surface, and ends near the 6th costochondral junction anteriorly. The fissure is formed by an invagination of the visceral pleura and contains interlobar pulmonary vessels. It is a key landmark in lobar anatomy, guiding radiologists and thoracic surgeons in identifying lobe boundaries and planning resections.

Synonyms

  • Major fissure of right lung

  • Right oblique interlobar fissure

  • Inferior fissure of right lung

Function

  • Divides the right lung into functional lobes for efficient ventilation and perfusion

  • Allows independent movement and expansion of lobes during respiration

  • Acts as a surgical and radiological landmark for segmental and lobar resections

  • Provides a plane containing interlobar pulmonary vessels

CT Appearance

Lung Window:

  • Seen as a thin curvilinear line of increased attenuation extending from the posterior lung apex (T4–T5) to the anterior diaphragm at the 6th rib

  • Best visualized when the fissure is air-filled on both sides, making the pleural surface appear sharp

  • May appear incomplete or variable in depth (fissural variants are common)

  • Pathology: displacement of the fissure can indicate lobar collapse, pleural effusion, or mass effect

Mediastinal Window:

  • Appears as a thin soft-tissue–like line separating lobes

  • Better for assessing pleural thickening, fissural effusions, or tumor invasion

  • Useful in staging lung carcinoma (tumor crossing fissures indicates advanced disease)

Contrast-enhanced CT (CECT):

  • Helps delineate interlobar vessels within the fissure

  • Enhances visualization of pathological thickening or tumor spread across the fissure

MRI Appearance

T1-weighted images:

  • Fissure itself appears as a low signal intensity line between high-signal lung parenchyma (when collapsed or fluid-filled)

  • Normally difficult to visualize due to air signal void in lung

T2-weighted images:

  • Fissure may appear as a low-signal linear structure

  • If fluid or effusion is present in the fissure, it appears bright hyperintense, enhancing fissural visibility

T1 Post-Contrast (Gadolinium-enhanced):

  • Normally, no significant enhancement of the fissure

  • Pathological thickening (inflammation, fibrosis, pleural tumor) shows linear or nodular enhancement

CT images

Oblique fissure of right lung anatomy CT coronal image -img-00000-00000

CT images

Oblique fissure of right lung anatomy CT coronal image -img-00000-00000_00001