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Topic

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Left crus of diaphragm

The left crus of the diaphragm is a tendinous and muscular structure that forms part of the diaphragm’s anchoring system. Along with the right crus, it originates from the lumbar vertebrae and ascends superiorly to contribute to the diaphragmatic central tendon. The left crus is shorter and thinner than the right crus but plays a crucial role in forming the esophageal hiatus and stabilizing the diaphragm during respiration.

The crura are important in radiology and surgery because they form key anatomical boundaries for abdominal and thoracic structures and are frequently evaluated in imaging for hernias, tumors, and retrocrural pathology.

Synonyms

  • Left diaphragmatic crus

  • Crus of diaphragm (left side)

  • Left lumbar crus

Origin, Course, and Insertion

  • Origin:

    • Arises from the anterior surfaces of the upper two lumbar vertebral bodies (L1–L2) and their intervertebral discs

  • Course:

    • Fibers pass superiorly and medially, blending with fibers of the right crus around the esophagus

    • Contributes to the formation of the esophageal hiatus

    • Some fibers interlace with those of the right crus to form a sling around the esophagus

  • Insertion:

    • Ascends to attach into the central tendon of the diaphragm

Relations

  • Anteriorly: Left adrenal gland, stomach fundus, splenic vessels

  • Posteriorly: Lumbar vertebral bodies (L1–L2)

  • Medially: Esophageal hiatus, right crus of diaphragm

  • Laterally: Left kidney and renal vessels, left diaphragmatic dome

Function

  • Provides structural anchoring of the diaphragm to lumbar vertebrae

  • Participates in formation of the esophageal hiatus, influencing gastroesophageal function

  • Assists in respiration by stabilizing the diaphragm during contraction

  • Contributes to prevention of gastroesophageal reflux by forming part of the esophageal sphincter mechanism

Clinical Significance

  • Hiatal hernias: Weakness or widening of the crus at the esophageal hiatus predisposes to hernia formation

  • Tumor spread: Retrocrural space may be a pathway for lymphoma or metastatic disease

  • Surgical relevance: Landmark in anti-reflux surgeries (e.g., fundoplication)

  • Imaging importance: Abnormal thickening may suggest tumor, infection, or fibrosis

MRI Appearance

T1-weighted images:

  • Crus appears as a low-to-intermediate signal intensity band

  • Clearly delineated against bright retrocrural and perinephric fat

T2-weighted images:

  • Crus demonstrates low-to-intermediate signal intensity

  • Pathology (inflammation, edema, tumor) shows increased signal intensity

T1 Fat-Sat Post-Contrast:

  • Normal crus enhances mildly and uniformly

  • Pathological crus shows heterogeneous or nodular enhancement in tumor, infection, or inflammatory infiltration

3D T2 SPACE / CISS:

  • Crus shows intermediate to mildly hyperintense signal compared to muscle

  • Surrounded by bright fat or CSF in adjacent retrocrural and mediastinal spaces

  • Excellent for defining esophageal hiatus morphology and crus thickness

CT Appearance

Non-Contrast CT:

  • Appears as a soft tissue density structure arising from L1–L2 vertebrae

  • Separated from surrounding retrocrural fat

  • Hypertrophy or asymmetry may be visualized in pathology

Post-Contrast CT:

  • Normal crus enhances mildly and homogeneously

  • Abnormal thickening or irregular enhancement may indicate tumor, infection, or fibrosis

  • Retrocrural lymphadenopathy or fluid collections may distort crus anatomy

MRI image

Left crus of diaphragm mri axial image

MRI image

Left crus of diaphragm mri coronal anatomy image-img-00000-00000