Systemic-pulmonary artery shunt: A rare cause of false-positive filling defect in the pulmonary arteries.

Computed tomographic (CT) pulmonary angiography is widely used for evaluation of pulmonary embolism. Intraluminal filling defects in the contrast enhanced pulmonary arteries are considered diagnostic of pulmonary emboli. We report a false-positive case where filling defects in the pulmonary artery were due to mixing of blood from a complex shunt or vascular malformation between the systemic arteries and pulmonary artery.