situs ambiguus
Definition: Situs ambiguus is the failure of asymmetry of unpaired organs and thus a condition where at least one organ shows a reversed orientation along the L-R axis. This condition has an estimated incidence at birth of 1/10,000. Situs ambiguus is frequently associated with isomerism.
Situs ambiguus is almost invariably associated with complex cardiovascular malformations as well as anomalies of the spleen and the gastrointestinal system.
Over 80% of children with situs ambiguus present with complex congenital heart disease. The spectrum of cardiac malformations that is seen in heterotaxia includes:
transposition of the great arteries (TGA)
double outlet right ventricle (DORV)
double inlet left ventricle (DOLV)
atrioventricular septal defects
- atrial septal defect
- ventricular septal defect
total anomalous pulmonary venous connection
Besides the cardiac anomalies, situs ambiguus is often associated with gastrointestinal manifestations:
right-sided stomach
medial liver (midline liver)
biliary tract developmental anomalies
intestinal malrotation
left-sided appendix
right-sided spleen
polysplenia
asplenia
Case records
isomerisms" class="spip_in">Case #10300
See also
heterotaxy (situs anomalies)
organ morphogenesis (visceral morphogenesis)
References
Peeters H, Devriendt K. Human laterality disorders. Eur J Med Genet. 2006 Sep-Oct;49(5):349-62. PMID: 16461029