Table 2.

Differential diagnostic considerations in case of suspected situs abnormality. Pertinent imaging findings listed for each type of situs arrangement.

Differential Diagnosis	X-Ray Findings	Abdominal US Findings	CT Findings
Situs ambiguous	Heart in left hemithorax with cardiac apex directed to the left; stomach bubble on right	Stomach on right; variable presence and number of spleens (if present, spleen typically located ipsilateral to stomach); liver typically bridging or on left side	Intestine may be mal- or non-rotated with variable location of appendix; venous drainage below diaphragm may be variable
Situs ambiguous with polysplenia (left isomerism)	Heart in left hemithorax with cardiac apex directed to the left; stomach bubble on right	Stomach on right; one or more spleens typically located along greater curvature of stomach; liver often bridging with midline gallbladder	Intestine may be mal- or non-rotated; bilateral bilobed lungs with hyparterial bronchi; IVC interruption with azygos or hemiazygos continuation
Situs ambiguous with asplenia (right isomerism)	Heart in left hemithorax with cardiac apex directed to the left; stomach bubble on right	Stomach on right; characteristic absence of spleen; liver often bridging with midline gallbladder	Intestine may be mal- or non-rotated; bilateral trilobed lungs with eparterial bronchi; IVC ipsilateral to aorta
Situs inversus totalis	Concordant location of cardiac situs (dextroverted) relative to mirror-image abdominal viscera	Stomach on right side; one spleen on right side along greater curvature of stomach; liver on left side with left- sided gallbladder	Thoracoabdominal viscera are in complete mirror-image configuration compared to normal situs solitus; no distinct venous drainage patterns