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Anatomy, Thorax, Triangle of Auscultation

Editor: Michael R. Zemaitis Updated: 10/7/2023 6:58:26 PM


The so-called "triangle of auscultation" is a clinically important region of the posterior thorax (see Image. Triangle of Auscultation). The area is so named for its value in assessing esophageal obstruction before the advent of roentgenography. Sounds of transiting material near the stomach's cardiac orifice can be heard over this area, allowing examiners to determine the presence of esophageal obstruction.[1] The relative thinness of the structures in the triangle also permits the assessment of other thoracic structures in aid of physical examination and surgical procedures.

This article discusses the anatomy of the triangle of auscultation and its importance in diagnosis and management.

Structure and Function

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Structure and Function

The auscultation triangle lies at the inferior angle of the scapula, and it has the following boundaries:[2]

  • Inferior: superior border of the latissimus dorsi muscle
  • Medial: lateral margin of the inferior aspect of the trapezius muscle
  • Lateral: lower aspect of the medial border of the scapula
  • Anterior (Floor):  rhomboid major muscle, fascial sheet, 6th and 7th ribs, and intercostal space

The auscultation triangle can be made prominent by instructing the patient to cross his arms over his chest before bending forward. Upper extremity adduction displaces the scapula and the triangle's muscular boundaries, reducing the sound barriers between the examiner's stethoscope and the thoracic structures under evaluation. Wheezing, rhonchi, rales, and other adventitious respiratory sounds are easier to distinguish in this region.[1][3][4][5]


Skeletal muscle formation occurs through the process of myogenesis.[6] The muscle cells originate from the paraxial mesoderm. This layer forms the somites, which later turn into the dermomyotomes and myotomes. 

Skeletal muscle development is divided into the myoblast, myotubule, and myofiber stages. Myoblasts, the skeletal muscle cell progenitors, form large, multinucleated cells under the influence of fibroblast growth factors. Myoblasts initially divide and fuse continuously, but the secretion of extracellular matrix proteins heralds their maturation into myotubules. Myofibers form from myotubule fusion; then, they stop dividing as fibroblast growth factors diminish. Myosatellite cells are multipotent cells persisting along the basal membrane that can give rise to new muscle tissue when activated.[7][8][9]

Blood Supply and Lymphatics

The triangle's blood supply is the same as that of its components.

  • Thoracodorsal artery: supplies the latissimus dorsi muscle [10]
  • Superficial cervical artery: supplies the trapezius muscle [11]
  • Dorsal scapular artery: supplies the rhomboid major muscle [12] 


Innervation of the auscultation triangle is also the same as that of its bounding structures.

  • Thoracodorsal nerve, aka the middle subscapular nerve, which innervates the latissimus dorsi [10]
  • Accessory nerve (cranial nerve XI) and the C3-C4 spinal nerves, which innervate the trapezius muscle [13]
  • Dorsal scapular nerve, which innervates the rhomboid major [14]


The muscles bordering the "triangle of auscultation" include: 

Lattisimus Dorsi 

This large muscle at the triangle's inferior border originates from the T7 to L5 spinous processes, thoracolumbar fascia, inferior angle of the scapula, lower ribs, and iliac crest. The latissimus dorsi inserts on the floor of the bicipital (intertubercular) groove of the humerus. The muscle adducts, medially rotates, and extends the arm at the glenohumeral joint.[10]


This muscle at the superior border of the triangle originates from the C7 to T12 spinous processes, occipital protuberance, ligamentum nuchae, and medial superior nuchal line. The trapezius inserts on the lateral clavicle, scapular spine, and acromion.

The muscle is divided into the superior, middle, and inferior divisions. The superior fibers extend the neck and elevate and superiorly rotate the scapula. The middle fibers adduct the scapula. The inferior fibers stabilize and assist in rotating the scapula.[11][15]

Rhomboid Major

This muscle originates from the T2-T5 spinous processes and inserts on the inner scapular border below the rhomboid minor. The rhomboid major retracts and rotates the scapula.[16]

Physiologic Variants

Anatomic variations differ in terms of which lung segment the auscultation triangle projects on from the surface. Cadaver studies reveal that the triangle can project on either the superior segment of the inferior lobe, posterior basal segment, or lateral basal segment. The projection was mirrored bilaterally in half of the cases.[3]

Surgical Considerations

The triangle of auscultation has advantages when used as an access route for various medical procedures due to the absence of large muscular structures within the area.

  • This region provides direct access to tumors originating from the ventral aspect of the scapula, particularly near the inferior angle. Osteochondromas have been excised through this window.[1] The approach minimizes blood loss since rhomboid major or trapezius dissection is avoided.[1]
  • A thoracotomy permits access to internal thoracic structures such as the lungs, pulmonary vasculature, heart, or aorta. This procedure may be performed emergently to evacuate a pericardial tamponade, control thoracic hemorrhage, administer internal cardiac massage, or cross-clamp the descending thoracic aorta. Access through the auscultation triangle reduces morbidity as it dispenses the need for a latissimus dorsi incision.[17]
  • A pleurectomy with access via the triangle reduces the need for a painful thoracotomy procedure. Recurrent spontaneous pneumothorax is a pleurectomy indication.[18][2]
  • A rhomboid intercostal nerve block can also be administered through this region to alleviate pain from rib fractures or a thoracotomy procedure. Typically, this nerve block is accomplished by injecting a local anesthetic agent into the fascial plane between the upper intercostal portion of the rhomboid and rhombic muscles.[19]

Clinical Significance

The triangle of auscultation offers a number of advantages when performing thoracic auscultation and surgical procedures. The thinness of the structures in this region allows better acoustics and access to internal thoracic structures, as discussed in the previous sections.[1]


(Click Image to Enlarge)
<p>Triangle of Auscultation

Triangle of Auscultation. The triangle of auscultation is bounded by the latissimus dorsi muscle (inferior), trapezius muscle (medial), scapula (lateral), and the rhomboid major, fascial sheet, 6th and 7th ribs, and intercostal space (anterior or floor).

Image courtesy S Bhimji MD



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