Oblique Fissure

fissura obliqua

The oblique fissure is a deep cleft present in both lungs that separates the lower lobe from the upper lobe (and on the right, also from the middle lobe). It is lined by visceral pleura, so the lobes can slide against each other. It runs diagonally downwards and forwards around the lung.

Anatomical Data

Structure & Supply

Location	Both lungs; on the chest wall it runs from about the level of the T2-T3 spinous processes behind, roughly along the 6th rib, to the 6th costochondral junction in front.
Parts	Visceral pleura lining both surfaces Costal, mediastinal and diaphragmatic parts

Biomechanics

Function & Actions

Allows the lobes to move separately and change shape as the lungs expand and the chest moves.

Clinical Relevance

Clinical Notes

The fissure is often incomplete, letting air pass between lobes; this collateral ventilation matters when choosing patients for endobronchial valves in emphysema. Fluid trapped in a fissure can look like a mass on X-ray and disappear with treatment of heart failure (a 'vanishing tumour'). Raising the arm above the head roughly lines up the oblique fissure with the medial border of the scapula.

Pathology

Common Injuries & Conditions

Interlobar Effusion

Pleural fluid collecting within a fissure, usually from heart failure. It can mimic a tumour on X-ray but resolves with treatment.

Fissural Displacement

Shift of the fissure towards a collapsed lobe or away from an expanding mass. It is an important sign of lobar collapse on imaging.

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