Reserve spaces of pleural cavity where lung doesn’t fully fill pleural reflection during quiet respiration; allow expansion on deep inspiration; sites of fluid collection.

Definition

• Recess = expanded pleural cavity part where parietal pleura reflects onto another part
• More obvious in expiration; lungs expand into them on deep inspiration

Two Main Recesses

1. Costodiaphragmatic recess
2. Costomediastinal recess

Costodiaphragmatic Recess

Formation: Costal pleura → diaphragmatic pleura reflection

Location: Inferior pleural cavity, both sides, between lung lower border + pleural lower limit

Extent:

Lung is 2 ribs higher than pleura at all 3 landmarks

Importance: most dependent part of pleural cavity; first site of effusion collection; thoracocentesis site; allows deep-inspiration lung expansion

Costomediastinal Recess

Formation: Costal pleura → mediastinal pleura reflection

Location: Anterior, behind sternum/costal cartilages, both sides

Right — small; often occupied by right lung anterior border even in quiet breathing

Left — larger; produced by cardiac notch; related to superficial cardiac dullness area

Pericardium relatively uncovered here; percussion = cardiac dullness; hyperinflated lung/pneumothorax may obliterate dullness

Minor Recesses

Retroesophageal recesses — mediastinal pleural reflections behind esophagus, both sides; small lung extensions; contribute to retrocardiac space on lateral CXR

Infracardiac recess — small, right pleural sac, below IVC between IVC + diaphragm; inconstant

Pleura Extending Beyond Thoracic Cage (5 sites)

Memory: 2 cervical + 1 right xiphicostal + 2 costovertebral = 5 sites Left xiphicostal angle excluded — left pleura displaced by heart

Applied Anatomy

Pleural Effusion

• First collects in costodiaphragmatic recess
• CXR: blunted costophrenic angle, meniscus sign, homogeneous basal opacity
• Signs: stony dullness, ↓breath sounds, ↓vocal fremitus, ↓chest expansion

Thoracocentesis

• Site: 8th ICS midaxillary line (9th also used)
• Technique: needle along upper border of lower rib (avoids neurovascular bundle in costal groove of rib above)
• Layers (midaxillary): skin → superficial fascia → serratus anterior → external intercostal → internal intercostal → innermost intercostal → endothoracic fascia → parietal pleura → pleural cavity

Costomediastinal recess / cardiac dullness

• Left recess corresponds to cardiac notch region
• Normal: superficial cardiac dullness; lost in emphysema/pneumothorax

Referred Pain

Pleural recesses are reserve spaces of the pleural cavity where lung does not completely fill the pleural reflection during quiet respiration. They allow lung expansion during deep inspiration and are clinically important because fluid collects in them.

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Definition

A pleural recess is an expanded part of the pleural cavity formed where one part of parietal pleura reflects onto another part.

Important idea:

• In expiration, recesses are more obvious.
• In deep inspiration, the lungs expand into them.

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Main Pleural Recesses

There are two main pleural recesses:

1. Costodiaphragmatic recess
2. Costomediastinal recess

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Costodiaphragmatic Recess

The costodiaphragmatic recess is the most important pleural recess.

Formation

It is formed at the reflection of:

Costal pleura → Diaphragmatic pleura

Location

• Inferior part of pleural cavity
• Present on both sides
• Lies between the lower border of lung and lower limit of pleural cavity

Extent

The lung is two ribs higher than the pleura at all three reference lines.

Importance

• Most dependent part of pleural cavity
• First site of pleural effusion collection
• Site approached during thoracocentesis
• Allows lung expansion in deep inspiration

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Costomediastinal Recess

Formation

It is formed at the reflection of:

Costal pleura → Mediastinal pleura

Location

• Anteriorly behind sternum and costal cartilages
• Present on both sides

Right Costomediastinal Recess

• Small
• Often occupied by anterior border of right lung even during quiet breathing

Left Costomediastinal Recess

• Larger than the right
• Produced by the cardiac notch of left lung
• Related to the area of superficial cardiac dullness

Clinical importance:

• In the left costomediastinal recess, the pericardium is relatively uncovered by lung.
• Percussion here gives cardiac dullness.
• Hyperinflated lung or pneumothorax may obliterate this dullness.

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Minor Pleural Recesses

Retroesophageal Recesses

• Formed by mediastinal pleural reflections behind the oesophagus.
• Present on right and left sides.
• Occupied by small extensions of lung.
• Contribute to the retrocardiac space on lateral chest radiographs.

Infracardiac Recess

• Small recess of the right pleural sac.
• Lies below the inferior vena cava between IVC and diaphragm.
• Inconstant.

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Sites Where Pleura Extends Beyond the Thoracic Cage

The parietal pleura extends beyond the bony thoracic cage at five sites.

Memory:

2 cervical + 1 right xiphicostal + 2 costovertebral = 5 sites

The left xiphicostal angle is not included because the left pleura is displaced by the heart.

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Clinical Significance

Pleural Effusion

Fluid in pleural cavity first collects in the costodiaphragmatic recess.

Chest X-ray:

• Blunting of costophrenic angle
• Meniscus sign
• Homogeneous opacity at lung base

Clinical signs:

• Stony dullness on percussion
• Reduced breath sounds
• Reduced vocal fremitus
• Reduced chest expansion

Thoracocentesis

Thoracocentesis is aspiration of fluid from the pleural cavity.

Common site:

• 8th intercostal space in midaxillary line
• 9th intercostal space may also be used depending on clinical situation

Technique:

• Needle is inserted along the upper border of the lower rib.
• This avoids the intercostal neurovascular bundle in the costal groove of the rib above.

Layers pierced in midaxillary line:

1. Skin
2. Superficial fascia
3. Serratus anterior
4. External intercostal muscle
5. Internal intercostal muscle
6. Innermost intercostal muscle
7. Endothoracic fascia
8. Parietal pleura
9. Pleural cavity

Costomediastinal Recess and Cardiac Dullness

The left costomediastinal recess corresponds to the cardiac notch region.

Clinical point:

• Normally gives superficial cardiac dullness.
• Dullness may be lost in emphysema or pneumothorax.

Referred Pain

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