Clinical Significance of Pleural Recesses
Costodiaphragmatic Recess — Clinical Importance
Pleural Effusion
The costodiaphragmatic recesses are the most dependent parts of the pleural cavity. Any excess fluid (pleural effusion) therefore accumulates here first.
Radiological appearance (PA CXR):
- The normally sharp, acute costophrenic angle becomes obliterated
- A radio-opaque shadow with a fluid meniscus line (concave upwards, higher laterally) replaces the normal clear angle
- Obliteration of the costophrenic angle is often the first radiological sign of pleural effusion — even a small volume (~200–300 ml) can cause this
Clinical detection:
- Decreased breath sounds and stony dullness on percussion over the site of effusion
- Decreased expansion on the affected side
Thoracocentesis (Paracentesis Thoracis)
Aspiration of fluid from the pleural cavity via the costodiaphragmatic recess.
Access site:
- 8th intercostal space in the midaxillary line (BDC)
- Alternatively: 9th or 10th intercostal space — within the extent of the costodiaphragmatic recess (VS)
- Patient positioned sitting upright and leaning forward
Technique: Needle inserted along the upper border of the lower rib in the chosen space to avoid the neurovascular bundle (vein, artery, nerve) that lies in the costal groove of the rib above.
Layers pierced (superficial to deep):
- Skin and superficial fascia
- Serratus anterior (in midaxillary line)
- External intercostal muscle
- Internal intercostal muscle
- Innermost intercostal muscle
- Endothoracic fascia
- Parietal pleura → enters pleural cavity
Costomediastinal Recess — Clinical Importance
Area of Superficial Cardiac Dullness
The left costomediastinal recess is large due to the cardiac notch of the left lung. In this region, the pericardium is not covered by lung — only by a double layer of pleura.
On percussion, this area gives dullness rather than resonance — called the area of superficial cardiac dullness. It overlies the right ventricle directly.
Clinical use: Loss of this area of dullness may indicate:
- Left-sided pneumothorax
- Lung hyperinflation (e.g., emphysema) — lung overexpands into the costomediastinal recess
Pleural Space Pathology — Quick Reference
| Condition | Contents of Pleural Space |
|---|---|
| Pleural effusion (hydrothorax) | Serous fluid |
| Haemothorax | Blood |
| Pneumothorax | Air |
| Pyothorax (empyema thoracis) | Pus |
| Chylothorax | Chyle (lymph) |
| Hydropneumothorax | Fluid + air |
Referred Pain from the Pleura
| Region of Pleura Irritated | Nerve Supply | Referred Pain Site |
|---|---|---|
| Costal pleura + peripheral diaphragmatic pleura | Intercostal nerves (T1–T11) | Thoracic and abdominal walls (along intercostal distribution) |
| Mediastinal pleura + central diaphragmatic pleura | Phrenic nerve (C3, C4, C5) | Tip of shoulder (supraclavicular nerves C3, C4, C5 supply the same skin) |
Examples: Right shoulder tip pain in right-sided pneumonia (phrenic territory) or right diaphragmatic irritation (e.g., subphrenic abscess, gallbladder disease). Left shoulder tip pain in splenic rupture.