Left lower lobe !
The left lower lobe is the bottom part of the left lung, filling the lower back of the chest, much of it hidden behind the heart on X-ray.
Official name: Inferior lobe of left lung
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What it is
The lower lobe of the left lung, below the oblique fissure, behind the heart.
What it does
Fills the lower back of the left chest.
Key facts
- Where
- Below oblique fissure, posteroinferior; segments superior, anteromedial, lateral and posterior basal
- Blood supply
- Pulmonary artery branches (gas exchange); bronchial arteries (nourish lung tissue)
- Nerve
- Pulmonary plexus: vagus (bronchoconstriction, secretion); upper thoracic sympathetic (bronchodilation)
- Function
- Gas exchange; consolidation blurs left hemidiaphragm (not heart border) on X-ray
Relations
- Above
- Left upper lobe across the upper part of the oblique fissure
- In front
- The lingula across the oblique fissure, and the pericardium over the left ventricle below the hilum
- Medial
- Descending thoracic aorta, which grooves the lobe behind the hilum, and the esophagus low down near the diaphragm
- Below
- Left dome of the diaphragm, with the spleen and the fundus of the stomach beneath it
- Behind
- Posterior ribs and intercostal spaces; the costodiaphragmatic recess extends below its lower edge
How to find it
Heard over the back from the medial end of the spine of the scapula (about T3) down to about T10, and low in the left axilla. Like the right lower lobe, its base moves down in deep inspiration.
On imaging
Collapse forms a triangular density behind the heart, with a sharp edge (sail sign), loss of the medial left hemidiaphragm and of the lower descending aorta outline, and a lowered left hilum. Consolidation blurs the hemidiaphragm, not the heart border.
Common problems
- Pneumonia (infection), asthma and COPD (narrowed airways).
- Lung cancer, often linked to smoking.
- Pulmonary embolism: a clot blocks an artery in the lung.
How it is diagnosed
Listening to the chest, chest X-ray, CT, breathing tests (spirometry), blood oxygen.
Treatment
- Depends on the cause: antibiotics, inhalers, oxygen; surgery removes a lobe or segment for some cancers.
Clinical notes
- Retrocardiac pneumonia is easily missed on a portable frontal film, especially in children and bedridden patients
- Its superior segment is a dependent site for aspiration when lying on the back, though aspiration is still more frequent on the right
Anatomical variants
- Intralobar pulmonary sequestration: a non-functioning piece of lung, most often in the posterior basal part of this lobe, supplied by an artery from the descending aorta
Development
Around week 5 the lung buds split into lobar buds: three on the right and two on the left, which is why the left lung lacks a middle lobe. On the left, the lower bud forms this lobe.
Related conditions
- α1-antitrypsin deficiency
- Echinococcosis (hydatid disease)
- Neonatal respiratory distress syndrome (hyaline membrane disease)
- Congenital diaphragmatic hernia
- Acute respiratory failure (hypoxaemic and hypercapnic)
- Atelectasis
- Community-acquired pneumonia
- Interstitial lung disease
- Acute respiratory distress syndrome (ARDS)
Test yourself
Think of the answer, then tap the question to see it.
Why is disease of the left lower lobe easily missed on a frontal chest X-ray?
Because the lobe lies behind the heart; the retrocardiac area must be checked for density and for the outline of the descending aorta.
What does collapse of the left lower lobe look like on a frontal chest X-ray?
A triangular density behind the heart with a sharp edge (sail sign), loss of the medial left hemidiaphragm and lower descending aorta outline, and a lowered left hilum.
Which structure grooves the left lower lobe behind the hilum?
The descending thoracic aorta, which lies medial to the lobe; the esophagus lies against it low down near the diaphragm.
What is intralobar pulmonary sequestration, and where in the left lower lobe is it usually found?
A non-functioning piece of lung supplied by an artery from the descending aorta, most often in the posterior basal part of the left lower lobe.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- lobus inferior pulmonis sinistri TA2 3308
- Official Spanish (DeCS)
- Lóbulo inferior del pulmón izquierdo DeCS D008168
- English (TA2)
- Inferior lobe of left lung
- Also called
- lower lobe of left lung · lobus dorsocaudalis
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Thorax, Lungs; 22.7 Embryonic Development of the Respiratory System (OpenStax (Rice University), 2022) · adapted, CC BY 4.0; Anatomy of the Human Body (20th ed.): The Respiratory Apparatus (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.
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Representative model, for educational purposes only.
