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Crural part of diaphragm

The crural parts of the diaphragm are two musculotendinous bands — the right crus and left crus — that arise from the lumbar vertebrae and insert into the central tendon of the diaphragm. They form the posterior muscular portion of the diaphragm, anchoring it firmly to the vertebral column.

  • Right crus: Larger and longer, originating from the bodies and intervertebral discs of L1–L3 (sometimes L4). It ascends to surround the esophageal hiatus, forming the esophageal sphincteric mechanism together with the lower esophageal sphincter (LES).

  • Left crus: Smaller and shorter, arising from L1–L2 vertebral bodies and intervertebral discs, joining the right crus and central tendon.

The crura are united by the median arcuate ligament, which arches over the aorta to form the aortic hiatus. The medial and lateral arcuate ligaments extend laterally, forming part of the diaphragm’s attachment to the posterior abdominal wall.

Clinically, the crural parts are critical in maintaining the anti-reflux barrier at the gastroesophageal junction. Weakness or laxity leads to hiatal hernia and GERD. Hypertrophy of the crura may be seen in conditions like achalasia or esophageal spasm.

Synonyms

  • Right crus of diaphragm

  • Left crus of diaphragm

  • Lumbar part of diaphragm

Function

  • Anchor the diaphragm to the vertebral column

  • Form the aortic hiatus (median arcuate ligament) and esophageal hiatus (right crus fibers)

  • Contribute to the anti-reflux barrier at the gastroesophageal junction

  • Aid in respiration by stabilizing the diaphragm during inspiration

  • Play a role in maintaining intra-abdominal and thoracic pressure gradients

MRI Appearance

T1-weighted images:

  • Crural muscle fibers appear as intermediate signal intensity bands arising from lumbar vertebrae

  • Surrounded by high-signal retroperitoneal and mediastinal fat

T2-weighted images:

  • Appear as intermediate-to-low signal muscular bands

  • Pathological edema or inflammation shows hyperintense signal

STIR:

  • Suppresses fat, clearly outlining crural muscle fibers

  • Highlights inflammatory changes, edema, or postoperative alterations

T1 Fat-Saturated (Pre-contrast):

  • Crural muscle fibers show intermediate signal, standing out against suppressed fat

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Normal crura enhance mildly and homogeneously

  • Asymmetric or focal enhancement suggests tumor invasion, inflammatory thickening, or post-surgical fibrosis

MRI Non-Contrast 3D Imaging:

  • Provides detailed view of esophageal hiatus, aortic hiatus, and crural attachments

  • Useful in surgical planning for hiatal hernia repair and evaluation of congenital anomalies

CT Appearance

CT Pre-Contrast:

  • Crura appear as soft tissue density muscular bands adjacent to lumbar vertebrae

  • Symmetry and thickness can be assessed

CT Post-Contrast:

  • Muscle enhances moderately

  • Useful for evaluating hiatal hernia, tumors, or asymmetric hypertrophy

MRI images

Crural part of diaphragm MRI coronal image anatomy image -img-00000-00000

CT image

Crural part of diaphragm CT axial image anatomy image -img-00000-00000

CT image

Crural part of diaphragm CT coronal