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Topic

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Lumbar part of diaphragm

The lumbar part of the diaphragm forms the posterior portion of the muscular diaphragm, arising from the lumbar vertebrae via the right and left crura and associated arcuate ligaments. The right crus originates from the bodies of L1–L3 (sometimes L4) vertebrae, while the left crus arises from L1–L2 (sometimes L3). Medially, the crura join to form the median arcuate ligament, which arches over the aorta to create the aortic hiatus. The lumbar diaphragm contributes to the formation of major openings: the aortic hiatus (T12), esophageal hiatus (T10), and is closely related to the caval opening (T8). This part of the diaphragm is essential for respiration and also serves as a passage for neurovascular structures between thorax and abdomen.

Synonyms

  • Lumbar diaphragm

  • Crural diaphragm

  • Posterior diaphragm

Function

  • Contracts to contribute to inspiration, pulling the central tendon downward to increase thoracic volume

  • Forms hiatuses for major structures (aorta, esophagus, thoracic duct)

  • Provides anatomical support between thoracic and abdominal cavities

  • Right crus contributes to lower esophageal sphincter function, preventing reflux

Arterial Supply

  • Inferior phrenic arteries (primary supply)

  • Contributions from the subcostal arteries and first two lumbar arteries

Venous Drainage

  • Drains via the inferior phrenic veins into the inferior vena cava (right) and left renal vein or IVC (left)

  • Additional drainage into the ascending lumbar and azygos venous systems

Nerve Supply

  • Motor innervation from the phrenic nerves (C3–C5)

  • Sensory innervation from phrenic, intercostal, and lower thoracic spinal nerves

MRI Appearance

T1-weighted images:

  • Lumbar diaphragm appears as a thin, low-signal intensity muscular band against bright retroperitoneal fat

  • Crura are visible descending along the lumbar vertebrae

T2-weighted images:

  • Muscular portion remains low signal intensity

  • Surrounding fat and abdominal organs appear hyperintense, providing natural contrast

  • Hypertrophy, fibrosis, or tumors may alter signal intensity

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, enhancing visualization of edema or inflammatory changes

  • Normal crura appear dark, whereas pathology (myositis, tumor infiltration) appears bright hyperintense

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal crural fibers show mild, uniform enhancement

  • Pathology (neoplasm, inflammatory lesions, or metastasis) demonstrates focal or heterogeneous enhancement

CT Appearance

Non-contrast CT:

  • Appears as a curved, soft tissue density muscular structure extending from lumbar vertebrae to central tendon

  • Right crus is larger and longer than the left

  • Provides margins of aortic and esophageal hiatuses

Contrast-enhanced CT (CECT):

  • Lumbar diaphragm enhances homogeneously with muscle contrast

  • Excellent for identifying crural hypertrophy, hiatus hernia, or retrocrural pathology (e.g., lymphoma, metastasis)

  • Axial and sagittal planes best demonstrate the aortic hiatus and crural anatomy

MRI image

lumbar part of diaphragm MRI axial image -img-00000-00000

CT image

lumbar part of diaphragm CT axial image -img-00000-00000