Situs inversus, (rare plural: sitūs inversi) short form of the Latin “situs inversus viscerum”, is a term used to describe the inverted position of chest and abdominal organs.

Terminology

The condition is called situs inversus totalis when there is a total transposition of abdominal and thoracic viscera (mirror image of internal organs' normal positioning). Normal positioning of the organs - as found in the majority of individuals is called situs solitus.

Much more rarely is transposition of the abdominal organs with a 'normal' left-sided heart, known variously as situs inversus incompletus, situs inversus partialis, or simply situs inversus with laevocardia ⁷.

Epidemiology

Situs inversus has a prevalence of approximately 1:10,000 and is higher in males (~1.5:1) ⁸.

Associations

Situs inversus is usually associated with dextrocardia (true mirror image) with only 3-5% incidence of congenital heart disease, most commonly transposition of the great vessels. Of these patients, 80% have a right-sided aortic arch. Situs inversus with laevocardia (which is much rarer: 0.00005%) congenital heart disease is found in 95% of patients ⁴.

Up to 20% of patients with situs inversus can have Kartagener syndrome ³ which comprises a subgroup of primary ciliary dyskinesia.

Situs inversus can be associated with both asplenia ⁵ or polysplenia (rarely) ⁶.

Complete situs inversus is associated with the absence of inferior vena cava ⁵.

Clinical presentation

Situs inversus is typically asymptomatic ⁸ unless associated with congenital heart disease.

Radiographic features

Plain radiograph

Imaging features on the chest radiograph to be evaluated are:

• location of the heart apex

• location of the aortic arch

• locations of stomach bubble and liver

See also

• situs classification

  • situs solitus

  • situs ambiguous

• heterotaxy syndrome