Diaphragm Anatomy and Differential Diagnosis

Original Editor - Carin Hunter based on the course by Rina Pandya
Top Contributors - Carin Hunter, Jess Bell, Wanda van Niekerk, Merinda Rodseth, Kim Jackson and Tarina van der Stockt

Anatomy of the Diaphragm[edit | edit source]

The diaphragm is a major muscle of respiration.[1]

  • It is a dome-shaped, "fibromuscular sheet" that separates the thorax from the abdomen[2]
  • It forms the floor of thorax and roof of abdomen[2][3]
  • The left side is lower than the right due to presence of the liver on the right[2]
  • The left side may also be located partially inferiorly due to the "push" by the heart[2][4][5]

Major Openings in the Diaphragm[edit | edit source]

Diaphragm Anatomy
  1. Caval hiatus: at the level of the T8 vertebra in the central tendon. Allows passage of the inferior vena cava and some right phrenic nerve branches.[2]
  2. Oesophageal hiatus: at the level of the T10. It allows the oesophagus, the right and left vagus trunks, the oesophageal branches of the left gastric vessels, and the lymph vessels to pass through.[2]
  3. Aortic hiatus: anterior to the T12 vertebral body between the crura. Allows the aorta, thoracic duct, and azygos vein to pass through.[2]

Nerve Supply[edit | edit source]

Cervical plexus phrenic nerve

The diaphragm is supplied by the right and left phrenic nerves:[2] C3, C4, C5 and sometimes C6. Each phrenic nerve divides into four trunks.[6]

  • Motor nerve supply:[7]
  1. Left hemidiaphragm is supplied by the left phrenic nerve
  2. Right hemidiaphragm is supplied by the right phrenic nerve
  • Sensory nerve supply:
    1. The phrenic nerve innervates the parietal pleura and the peritoneum which covers the diaphragm's central surfaces. The periphery of the diaphragm is innervated by the bottom six intercostal nerves.[2]
    2. The phrenic nerve is made up of large-diameter myelinated, small-diameter myelinated, and unmyelinated fibres. The large diameter fibres fire when the diaphragm contracts while the small diameter fibers fire throughout respiration.[8]
      • Activation of the phrenic nerve modulates the sympathetic motor outflow.[2]
      • Phrenic afferents are also involved in the somatosensation of the diaphragm and they make individuals aware of their breathing while they are awake.[2]

Vascular Supply[edit | edit source]

Arterial supply:

  • Inferior phrenic artery from abdominal aorta
  • Superior phrenic artery
  • Pericardiophrenic, musculophrenic arteries

Venous supply:

  • Inferior phrenic vein

Fascial Attachments[edit | edit source]

1. Vertebrae[edit | edit source]

  • Medial lumbocostal arch[2]
    • A tendinous arch in the fascia which covers psoas major
    • Medially, it attaches to the side of the L1 vertebral body
    • Laterally, it attaches at the front of the L1 transverse process
  • Lateral lumbocostal arch[2]
    • A tendinous arch in the fascia which covers the upper portion of quadratus lumborum
    • Medially, it attaches to the front of the L1 transverse process
    • Laterally, it attaches to the lower border of rib 12

2. Muscles[edit | edit source]

  • Quadratus lumborum (QL) attaches to the inferior portion of the 12th rib. A part of the diaphragm attaches to this rib's superior portion. The fascia is continuous between these attachments.[9]
  • The psoas muscle is in a similar area as the QL. It blends with the fascia at the proximal end of the posterior portion of the diaphragm.[9]

Aetiology of an Elevated Diaphragm[edit | edit source]

An elevated hemidiaphragm may be due to both direct and indirect causes.

The causes can be grouped into three categories based on the location of the cause, including:[7][9]

  1. Above the diaphragm
    • Decreased lung volume
    • Atelectasis/collapse
    • Prior lobectomy or pneumonectomy
    • Pulmonary hypoplasia
  2. At the level of the diaphragm
    • Phrenic nerve palsy
    • Diaphragmatic eventration
    • Contralateral stroke: usually middle cerebral artery (MCA) distribution
  3. Below the diaphragm
    • Abdominal tumour, e.g. liver metastases or primary malignancy
    • Subphrenic abscess
    • Distended stomach or colon, including Chilaiditi sign/syndrome

Differential Diagnosis for Elevated Diaphragm[edit | edit source]

Other situations which may mimic an elevated hemidiaphragm include:[7]

Aetiology for Paralysis of the Diaphragm[edit | edit source]

Diaphragmatic paralysis occurs when the nerve supply is interrupted. This interruption might occur in the phrenic nerve itself, at the cervical spinal cord, or in the brainstem. However, it is most commonly caused by a phrenic nerve lesion:[6][10]

  • Mechanical trauma: such as nerve damage / ligation during surgery
  • Compression: due to a chest cavity tumour
  • Myopathies: including myasthenia gravis
  • Neuropathic: including conditions such as diabetic neuropathy, inclusion body myositis, dermatomyositis, multiple sclerosis, anterior horn cell disease, chronic demyelinating disease, and neuralgic myopathy
  • Inflammation: a number of systemic diseases can cause inflammation in the phrenic nerve / diaphragm, which results in diaphragmatic palsy. Examples include:
    • Viral infections (e.g. HIV, West Nile virus and poliomyelitis virus)
    • Bacterial infections (e.g. Lyme disease)
    • Non-infectious causes (e.g. sarcoidosis and amyloidosis)
  • Idiopathic: around 20 percent of cases have no obvious cause

Differential Diagnosis for Paralysis of the Diaphragm[edit | edit source]

  • Alveolar hypoventilation
  • Anterior horn cell or neuromuscular junction disease
  • Cerebral haemorrhage
  • Cervical fracture
  • Decreased pulmonary compliance
  • Guillain-Barre syndrome
  • Myasthenia gravis
  • Peripheral neuropathies
  • Pleural adhesions[6]

Symptoms of Diaphragmatic Weakness[edit | edit source]

  1. Unilateral weakness: Often asymptomatic and detected incidentally. Patients show limitations in exercise capacity, lower oxygen saturation levels:[6]
    • A third of patients complain of exertional breathlessness
    • Dyspnoea at rest with co-morbidities such as cardiopulmonary conditions
  2. Bilateral weakness: dyspnoea at mild exertion to dyspnoea at rest:[6]
    • Further compromise→ orthopnoea
    • Progressive hypoventilation → hypercapnia and right heart failure. Worse during sleep.

Paradoxical Breathing[edit | edit source]

Paradoxical Breathing

Paralysis of the diaphragm results in a "paradoxical movement". The affected side moves up during inspiration and down during expiration.[10]

  • Unilateral diaphragmatic paralysis is frequently asymptomatic and is often found incidentally on x-ray.[10]
  • Bilateral paralysis can result in poor exercise tolerance, orthopnoea and fatigue. There will also be a restrictive deficit on lung function tests.[10]

References[edit | edit source]

  1. Fayssoil A, Behin A, Ogna A, Mompoint D, Amthor H, Clair B, Laforet P, Mansart A, Prigent H, Orlikowski D, Stojkovic T, Vinit S, Carlier R, Eymard B, Lofaso F, Annane D. Diaphragm: Pathophysiology and Ultrasound Imaging in Neuromuscular Disorders. J Neuromuscul Dis. 2018;5(1):1-10
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 Bains KN, Kashyap S, Lappin SL. Anatomy, Thorax, Diaphragm. StatPearls [Internet]. 2020 Aug 15.
  3. Kurian J. Chest Wall and Diaphragm. InPediatric Body MRI 2020 (pp. 159-192). Springer, Cham.
  4. Bordoni B, Purgol S, Bizzarri A, Modica M, Morabito B. The influence of breathing on the central nervous system. Cureus. 2018 Jun;10(6).
  5. Oliver KA, Ashurst JV. Anatomy, Thorax, Phrenic Nerves. InStatPearls [Internet] 2020 Jul 27. StatPearls Publishing.
  6. 6.0 6.1 6.2 6.3 6.4 Kokatnur L, Vashisht R, Rudrappa M. Diaphragm Disorders. [Updated 2021 Aug 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470172/
  7. 7.0 7.1 7.2 Patel PR, Bechmann S. Elevated Hemidiaphragm. [Updated 2021 Aug 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559255/
  8. Nair J, Streeter KA, Turner SM, Sunshine MD, Bolser DC, Fox EJ, Davenport PW, Fuller DD. Anatomy and physiology of phrenic afferent neurons. Journal of neurophysiology. 2017 Dec 1;118(6):2975-90.
  9. 9.0 9.1 9.2 Pandya R. Diaphragm Anatomy and Differential Diagnosis Course. Physioplus, 2021.
  10. 10.0 10.1 10.2 10.3 TeachMe Anatomy. The diaphragm. Available from: https://teachmeanatomy.info/thorax/muscles/diaphragm/ (accessed 30 November 2021).