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/
