48 Right Isomerism with Asplenia

Clinical Presentation

A newborn presents with cyanosis and tachypnea.

Figure 48A

Radiologic Findings

A frontal chest radiograph (Fig. 48A1) shows the stomach bubble in a left paramedian location and the transverse liver. There is a levocardia. In the lateral chest radiograph (Fig. 48A2), the upper lobar bronchi are located in similar horizontal levels. The pulmonary arterial shadow is seen mostly in front of the airway. Both lungs show increased interstitial markings due to pulmonary venous hypertension secondary to obstructive type of total anomalous pulmonary venous connection.

Figure 48B T1-weighted coronal MRI shows right-isomeric branching pattern of the bronchi (arrows), juxtaposition of the aorta and inferior vena cava (IVC) on the right side, and a left-sided stomach. All pulmonary veins make a confluence at a vertical vein (VV) that drains into the portal vein. AA, aortic arch.

Figure 48C Chest radiographs in a patient with left isomerism. The frontal view (1) shows symmetrically long bronchi, right-sided stomach, and levocardia. The lateral view (2) shows end-on shadows of both upper lobar bronchi in similar horizontal levels. The pulmonary arteries are seen above and behind the upper lobar bronchi.

Diagnosis

Right isomerism with transverse liver and asplenia. A T1-weighted MRI (Fig. 48B) shows symmetrically short bronchi. Neither right nor left pulmonary artery is above the main bronchus. The abdominal aorta and inferior vena cava are juxtaposed on the right side of the spine. The pulmonary veins make a confluent channel to connect to the portal vein via a vertical vein.

Differential Diagnosis

Left isomerism: Transverse liver and abnormally positioned stomach may also be seen in left isomerism. However, left isomerism tends to have one side of the liver larger than the other (Fig. 48C).

Figure 48D Diagrams show visceral heterotaxy with thoracic right isomerism and asplenia (1) and visceral heterotaxy with thoracic left isomerism and polysplenia (2) gastric bubble; IVC, inferior vena cava; PA, pulmonary artery; SVC, superior vena cava