Table 2 Heterotaxy diagnostic criteria from the National Birth Defects Prevention Study (modified from Lin et al. [1] and Foerster et al. [103]). Classically, the diagnosis of HTX requires three out of eight features

1. Characteristic congenital heart defect

 a. Pulmonary venous anomalies (TAPVR, PAPVR)

 b. Atrial anomalies (atrial situs ambiguus or inversus, common atrium)

 c. Common atrioventricular canal (or septal) defects

 d. Ventricular abnormalities (hypoplastic or single left ventricle, hyoplastic or single right ventricle, ventricular malposition (e.g. L-loop, superior-inferior, criss-cross))

 e. Ventriculo arterial alignment abnormalities (double-outlet ventricle, D-loop TGA, L-loop TGA, truncus arteriosus, TOF (including TOF/PS, TOF/PA, and TOF/APV))

 f. Ventricular outflow abnormalities (subvalvar/valvar PS, PA with intact ventricular septum, PA with ventricular septal defect (not TOF-type), valvar or subvalvar aortic stenosis, coarctation of the aorta)

2. Biliary atresia

3. Abdominal situs abnormality

 a. Abdominal situs inversus

 b. Midline or transverse liver

 c. Midline aorta

 d. Ipsilateral aorta and IVC

4. Spleen abnormality

 a. Asplenia

 b. Polysplenia

 c. Single right-sided spleen

5. Isomerism of bronchi

 a. Bilateral left bronchial morphology (bilateral hyparterial bronchus)

 b. Bilateral right bronchial morphology (bilateral eparterial bronchus)

6. Isomerism of lungs

 a. Bilateral two lobes (left-sidedness)

 b. Bilateral three lobes (right-sidedness)

7. Similar morphology of atrial appendages (“atrial isomerism”)

8. Two of the following

 a. A systemic venous anomaly

  1. Bilateral SVC

  2. Interrupted IVC

  3. Unroofed (absent) coronary sinus

 b. Intestinal malrotation (nonrotation, incomplete rotation, reverse rotation)

 c. Absent gallbladder