Thoraco-abdominal viscera have unique morphological asymmetry, unlike the body's external organs. Heterotaxy syndrome is a disorder in which there is a loss of normal left to right asymmetry of thoraco-abdominal viscera and their naturally proscribed spatial relationship. It has multiple anatomical alterations, culminating into physiological and hemodynamic consequences. It is divided into two groups on the basis of morphology of the two atrial appendages. These subgroups are - 1) Isomerism of right atrial appendage (asplenia syndrome); 2) Isomerism of left atrial appendage (polysplenia syndrome); Patients from group I, usually have severe cardiac malformations and present early. They may have duct dependent lesions and eventually may undergo Fontan surgery. However, extracardiac anomalies are more common in group II. All the patients must be evaluated in detail to rule out anomalies like gut-malrotation. Patients must be provided with special care for their susceptibility to infection due to absence of spleen or presence of splenic malfunction. Majority of these patients may have genetic link and may present in families. Hence, genetic evaluation is necessary before assuming long term outcome.
Keywords: AVSD; Asplenia; Heterotaxy syndrome; Isomerism of atrial appendage; Ivemark syndrome; Polysplenia; Situs ambiguous.