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Topic

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Crura of diaphragm

The crura of the diaphragm are tendinous structures that arise from the lumbar vertebrae and form part of the muscular origin of the diaphragm. There are two crura:

  • The right crus is larger and longer, arising from the anterior surfaces of the L1–L3 vertebrae and their intervertebral discs. It ascends to form part of the esophageal hiatus.

  • The left crus is shorter, arising from the L1–L2 vertebrae and their discs, joining its fibers with the right crus across the midline.

Together, the crura form the median arcuate ligament, arching over the aorta to create the aortic hiatus. They play a key role in anchoring the diaphragm to the vertebral column and maintaining the integrity of the thoracic and abdominal cavities.

Synonyms

  • Right and left crura of diaphragm

  • Lumbar part of diaphragm

  • Tendinous origins of diaphragm

Function

  • Provide anchorage of the diaphragm to the lumbar vertebrae

  • Contribute to the formation of the esophageal hiatus (right crus) and aortic hiatus (both crura via median arcuate ligament)

  • Help regulate esophageal sphincter competence, preventing reflux during respiration

  • Play a role in respiration and intra-abdominal pressure regulation

MRI Appearance

T1-weighted images:

  • Crura appear as low signal intensity structures relative to surrounding fat and muscle

  • Distinct against the hyperintense retrocrural fat in the posterior mediastinum

  • Useful for identifying asymmetry, hypertrophy, or infiltration

T2-weighted images:

  • Crura remain low signal intensity, surrounded by brighter fat and adjacent organs

  • Abnormal thickening, edema, or tumor infiltration appears hyperintense compared to normal fibers

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, improving contrast between crural fibers and surrounding retrocrural fat

  • Pathological processes (inflammation, edema, tumor) appear hyperintense

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal crura show minimal enhancement

  • Abnormal lesions (metastasis, lymphoma, infection) may demonstrate enhancing soft tissue masses or irregular thickening

CT Appearance

Non-contrast CT:

  • Crura appear as soft tissue density bands extending vertically along the lumbar vertebrae, best seen posterior to the aorta

  • Surrounded by low-density retrocrural fat, providing contrast

Contrast-enhanced CT (CECT):

  • Crura are clearly defined as enhancing muscular bands

  • CT is excellent for assessing crural hypertrophy (common in hiatal hernia, GERD), retrocrural lymphadenopathy, or tumor infiltration

  • Clearly delineates the esophageal and aortic hiatus formed by the crural fibers

MRI images

crura of diaphragm anatomy MRI coronal image -img-00000-00000

MRI images

Crus of diaphragm anatomy MRI axial image -img-00000-00000

CT image

Crus of diaphragm anatomy CT axial image -img-00000-00000