Table 1.

Summary table of major features of the situs ambiguous subtypes.

Situs Ambiguous	Situs ambiguous with polysplenia (left isomerism)	Situs ambiguous with asplenia (right isomerism)
Etiology	Sporadic defect in body lateralization around day 28 of gestation	Sporadic defect in body lateralization around day 28 of gestation
Incidence	Between 1:10,000 and 1:20,000	Between 1:10,000 and 1:20,000
Gender ratio	2:1 female ratio	2:1 male ratio
Age predilection	Congenital aberration seen at birth, but may be diagnosed in infancy or later in life depending on patient’s need for imaging	Congenital aberration seen at birth, but may be diagnosed in infancy or later in life depending on patient’s need for imaging
Risk factors	No known risk factors	No known risk factors
Treatment	None if patient truly has isolated levocardia. Surgery if cyanotic heart lesion present	None if patient truly has isolated levocardia. Surgery if cyanotic heart lesion present; vaccination if anatomically asplenic
Prognosis	Often comorbid with CHD (50–90%), which, if severe, may cause death at a young age. Prognosis is good if heart lesion not present or is repaired.	Often comorbid with CHD (nearly 100%), which, if severe, may cause death at a young age. Prognosis otherwise guarded due to risk of overwhelming sepsis.
Findings on imaging	Discordant position of cardiac situs relative to abdominal viscera. Stomach often on right side, with one or more spleens. Intestine may be mal- or non-rotated. Liver is often bridging with midline gallbladder. IVC interruption with azygos or hemiazygos continuation. Bilateral bilobed lungs with hyparterial bronchi.	Discordant position of cardiac situs relative to abdominal viscera. Stomach often on right side, with no spleen present. Intestine may be mal- or non-rotated. Liver is often bridging with midline gallbladder. IVC ipsilateral to aorta. Bilateral trilobed lungs with eparterial bronchi.