Heterotaxy is an abnormal and disorganized arrangement of organs within the abdominal cavity, in contrast to the normal orderly arrangement seen in situs inversus or situs solitus. There are two main categories of heterotaxy: situs ambiguous with polysplenia or left isomerism, and situs ambiguous with asplenia or right isomerism. Situs ambiguous with left isomerism involves bilateral symmetry of organs and a lower prevalence of congenital heart disease, while situs ambiguous with right isomerism involves more complex congenital heart defects and cyanosis.

1. Heterotaxy

3. Define
• Known as situs ambiguous, is defined as the abnormal and
disorganised arrangement of organs and vessels within the abdominal
cavity

4. Differential diagnosis
• This is in contrast to the orderly arrangement that occurs in situs
inversus or situs solitus

5. 2 Categories
• situs ambiguous with
polysplenia
• Left isomerism
• Bilateral left-sidedness
• Midline position of the abdominal
organs and multiple
spleens/splenules
• Lower prevalence of congenital
heart disease (50–90%)
• Less severe defects than
• Situs ambiguous with asplenia
• Right isomerism
• Complex CHD

6. Left isomerism: No cyanosis
• Many spleen
• Bilaterally symmetrical liver
• Bilateral bi-lobed lungs
• Bilateral hypo-arterial bronchi (left isomerism)
• Bilateral SVC
• Intrahepatic interruption of the IVC with azygous or hemi-azygous continuation
• Common atrium
• AVCD
• Hypoplasia or absence of one ventricle
• LVOT/RVOT obstruction
• DORV
• 50% dextrocardia
• Kartagener’s syndrome

7. Right isomerism :Cyanosis
• No left atrium to receive pulmonary venous drainage(TAPVC)
• Venous drainage into a systemic vein is seen in > 50%
• Infancy
• Transposition of the great arteries
• AVCD
• Ventricular hypoplasia or single ventricle physiology
• Pulmonary atresia
• Pulmonary vein obstruction
• 80%-90% die in the first year

8. Easy to follow
• http://www.ncbi.nlm.nih.gov/p
mc/articles/PMC3116098/