Oblique fissure

Jack Ren et al.

The oblique fissures (also called the major fissures or greater fissures) are bilateral structures in both lungs separating the lung lobes. 

The superior part of the right oblique fissure separates the right upper lobe from the right lower lobe and the inferior part separates the right middle lobe from the right lower lobe

Its approximate position can be marked by a curved line on the thoracic wall that begins roughly at the spinous process of the T4 level of the thoracic spine, then crosses the fifth intercostal space laterally, and follows the contour of the right 6th rib anteriorly 1.

The left oblique fissure separates the left upper lobe from the left lower lobe.

Its approximate position can be marked by a curved line on the thoracic wall that begins between the spinous processes of vertebrae T3 and T4, then crosses the fifth intercostal space laterally, and follows the contour of the 6th rib anteriorly 1.

The oblique fissures are highly variable and may be incomplete or absent, thus complicating the identification of various pathological processes. In the majority of cases the left oblique fissure is located at a higher level and courses more vertically than the right oblique fissure 2.

Both oblique fissures can present as incomplete fissures (48% on the right compared with 43% on the left). Absence of the the oblique fissure is rare and occurs in <1% of the population 2.

The oblique fissures can be visualised on both conventional radiography and computed tomography (CT) scans. For transthoracic biopsies, especially those for lesions located in the upper lobes, knowledge of the exact anatomy of the oblique fissures is essential to avoid crossing the oblique fissures.

On a lateral radiograph, the right oblique fissure ends at the anterior costophrenic angle and the left oblique fissure ends about 5 cm posterior to the anterior costophrenic angle 3.

Occasionally the superior aspect of the left major fissure may mimic pneumomediastinum, so called pseudopneumomediastinum.

Thoracic anatomy
Chest x-ray
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Article information

rID: 34281
System: Chest
Section: Anatomy
Synonyms or Alternate Spellings:
  • Major fissure
  • Greater fissure

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Cases and figures

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    Figure 1
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    Case 1: pulmonary pseudotumour
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    Case 2: oblique fissure haematoma
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