Minor Recesses and Sites of Pleural Extension Beyond the Thoracic Cage
Minor Pleural Recesses
In addition to the two main recesses (costodiaphragmatic and costomediastinal), three smaller recesses are described:
Retroesophageal Recesses (Right and Left)
- Formation: Reflections of the mediastinal pleura behind the oesophagus, from both sides
- Each recess is occupied by a small extension of the corresponding lung
- Radiological significance: They contribute to the retrocardiac space seen on lateral chest radiographs
Infracardiac Recess
- A small recess of the right pleural sac
- Extends beneath the inferior vena cava (between the IVC and the diaphragm)
- Present only on the right side; inconstant
Sites Where Pleura Extends Beyond the Thoracic Cage
At five sites, the parietal pleura projects outside the confines of the bony thoracic cage. The pleura is vulnerable to inadvertent puncture at these locations during surgical procedures.
| Site | Side | Anatomical Detail | Surgical Significance |
|---|---|---|---|
| Root of neck (cervical dome of pleura) | Both sides | Extends ~2.5 cm above the medial one-third of the clavicle and ~5 cm above the first costal cartilage | Risk during procedures in the neck — e.g., stellate ganglion block, subclavian venous access, neck dissection |
| Right xiphicostal angle | Right only | Pleura descends below the costal margin at the right xiphisternal/xiphicostal angle | Risk during upper abdominal surgery on the right — e.g., liver procedures |
| Costovertebral angles | Both sides | Pleura extends below the 12th rib at the lateral border of erector spinae — 2 cm lateral to the 12th thoracic spine | Risk during posterior surgical exposure of the kidney (nephrectomy, renal surgery through the loin) |
Mnemonic for 5 sites: 2 (bilateral cervical) + 1 (right xiphicostal) + 2 (bilateral costovertebral) = 5 sites total
The left xiphicostal angle is not a site of pleural extension — the left pleura does not dip into the left xiphicostal angle.
Applied Anatomy: Needle Pleurocentesis
The costodiaphragmatic recess is accessed clinically for pleural aspiration (thoracocentesis / paracentesis thoracis):
- Needle is inserted into the 8th intercostal space in the midaxillary line (BDC) or 9th–10th intercostal spaces (VS) — both are valid exam answers
- The needle passes along the upper border of the lower rib to avoid the neurovascular bundle (vein, artery, nerve = VAN) which runs in the subcostal groove of the rib above
- Layers pierced: skin → superficial fascia → serratus anterior → external/internal/innermost intercostal muscles → endothoracic fascia → parietal pleura → pleural cavity