RAI vs LAI

Situs ambiguous - Stomach position should NOT be used as a means of diagnosis as it can be in any location. - Most display normal karyotype (however, 10% associated with genetic abnormality in multiple types) Right Atrium Isomerism - Key to diagnosis is juxtaposition of Aorta and IVC - Asplenia (postnatal diagnosis) - Often associated with complex CHD, including TAPVR (due to duplication of right atrium, as PV returns to left atrium normally) - Less associated with biliary atresia (gallbladder visible) - Prognosis depends on severity of CHD Left Atrium Isomerism - Key to suspicion is detection of interrupted IVC (no visualization of IVC in front of Aorta, and instead dilated Azygos vein can be seen => rotate to coronal view, where 2 parallel vessels can be seen with opposite flow directions. 2 opposite flow arch views can also be seen) - Polysplenia - Bradycardia secondary to absence of pacing nodes (usually situated in right atrium) - More associated with biliary atresia (less likely if gallbladder visible, however, definitive diagnosis can only be made postnatally, by close observation during first 2 months of neonatal life -> observe for presence of jaundice and clay-colored stool) - Sometimes associated with CHD - Prognosis depends on severity of CHD ** Prenatally, LAI fairs worse than RAI due to possibility of bradycardia. However, postnatally, LAI fairs better, due to its association with less complex heart problems. Conversely, of RAI postnatally is generally poor due to association with complex CHD. Also, children may succumb to infections due to association with asplenia**