- Innervation
- Phrenic nerve
- Roots: C3, C4, C5 (“C3, 4, 5 keeps the diaphragm alive”)
- Provides motor innervation to the entire diaphragm.
- Provides sensory innervation to the central part of the diaphragm (peritoneum and pleura).
- Intercostal nerves (lower 6-7)
- Provide sensory innervation to the peripheral diaphragm.
- Structures Piercing the Diaphragm
- Mnemonic: “I (IVC) 8 10 Eggs (Esophagus) At (Aorta) 12”
- T8 (Caval opening):
- Inferior Vena Cava (IVC)
- Right phrenic nerve branches
- T10 (Esophageal hiatus):
- T12 (Aortic hiatus):
- Aorta
- Thoracic duct
- Azygos vein
- Diaphragmatic Hernias
- Hiatal Hernia
- Sliding Hernia (Type 1): Most common (>95%). Gastroesophageal (GE) junction and stomach cardia slide upward into the thorax. Associated with GERD.
- Paraesophageal Hernia (Type 2): Gastric fundus herniates into the thorax alongside the esophagus. GE junction remains in normal position. Risk of strangulation.
- Congenital Diaphragmatic Hernia (CDH)
- Bochdalek Hernia: Most common CDH (~95%). Defect is posterolateral, usually on the left. Abdominal contents herniate into the thorax, leading to pulmonary hypoplasia. Presents with respiratory distress in a newborn.
- Morgagni Hernia: Rare. Defect is anteromedial.
- Clinical Correlations
- Paralysis of Hemidiaphragm:
- Due to phrenic nerve injury (e.g., thoracic surgery, tumor compression).
- On CXR, the affected hemidiaphragm is elevated.
- On fluoroscopy (“sniff test”), there is paradoxical upward movement of the paralyzed side during inspiration.
- Referred Pain (Kehr’s Sign):
- Irritation of the diaphragmatic peritoneum (e.g., by blood from splenic rupture, subphrenic abscess, cholecystitis) can cause referred pain to the shoulder tip (C3-C5 dermatome).
- Hiccups (Singultus):
- Involuntary, spasmodic contraction of the diaphragm, causing sudden inhalation that is stopped by glottic closure.
- Can be caused by phrenic nerve irritation.