Alagille syndrome is associated with peripheral pulmonary artery stenosis which can cause pulmonary perfusion defects, leading to systemic recruitment of vessels and pulmonary hypertension. This is well demonstrated in a young patient via cardiac MRI including pulmonary perfusion and MRA, allowing for assessment of the right heart function, pulmonary artery dimensions, disease distribution and severity, without the need for ionizing radiation.

Previous CTPA was reported as mild narrowing of the right main pulmonary artery only. Changes within the left upper lobe and lower lobe segmental vessels were not well demonstrated. In contrast to MRI, CTPA uses ionizing radiation and can underestimate the extent and severity of the disease with no assessment of pulmonary perfusion and right heart function. Cardiac MRI and pulmonary MRA is therefore the modality of choice where available.