Heterotaxy syndrome

Heterotaxy syndrome or situs ambiguus (also commonly, but etymologically less correctly, spelled situs ambiguous) is a disturbance in the usual left and right distribution of the thoracic and abdominal organs which does not entirely correspond to the complete or partial mirror image.

It occurs from an early embryological developmental disturbance with most cases being sporadic. It is also classified under the group of cardiosplenic syndromes.

The true incidence is not known, but some sources have estimated it to be around 1 per 8,000-25,000 live births. Approximately 20-25% are associated with the immotile cilia syndrome (including Kartagener syndrome).

This is dependent on severity of the isomerism and presence of associated abnormalities. Cyanotic congenital heart disease is the main presentation in right isomerism. Left isomerism tend to present later in chilhood or even in adulthood, since it is less associated with complex congenital heart disease. Intestinal malrotation with midgut volvulus may be also be a presenting feature.

Bronchial anatomy accurately reflects atrial situs. The bronchial anatomy on the left and right can be recognised on a well penetrated radiograph and consists of two main bronchi that are anatomically different:

In situs ambiguus, there is duplication of either the hyparterial or eparterial bronchus. The associated atria are also duplicated and there are specific changes below the diaphragm (although not left-sided or right-sided duplication) 1.

Imaging features can be extremely complex.  

There is duplication of the left or right-sided intra-thoracic contents with associated changes below the diaphragm. Classically, there is malposition of the liver, stomach and spleen (which may be absent). Additionally, the vascular supply above and below the diaphragm may be altered significantly (including SVC duplication1.

Known as polysplenia syndrome:

Known as asplenia syndrome:

Assessment of the intra-thoracic contents can be made with plain film, echocardiography, CT and MRI as well as angiography. Below the diaphragm, the abdominal contents can be imaged ultrasound, GI contrast studies, CT and MRI.

A minimal work up should include 1:

  • chest radiograph
  • echocardiogram: to assess for congenital heart disease
  • abdominal ultrasound: to assess intra abdominal contents (especially spleen)
  • upper GI series: to rule out malrotation

Treatment is completely dependant on the malformations (that occur to varying degrees) and the impact that they have clinically.

Specific treatment of congenital heart disease can be seen in their separate articles.

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Article information

rID: 7420
System: Paediatrics
Sections: Syndromes, Anatomy
Tag: variant
Synonyms or Alternate Spellings:
  • Situs ambiguous
  • Heterotaxy
  • Cardiosplenic syndromes
  • Situs ambiguus

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Cases and figures

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    Heterotaxy
    Case 1
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    Axial CECT in pat...
    Case 2: polysplenia
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    Case 3: on ultrasound
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    Case 4: right isomerism
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    Case 5
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    Case 6
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