Abstract
This report describes a rare case of a systemic artery-to-pulmonary artery fistula initially misdiagnosed as a pulmonary arteriovenous malformation in a 64-year-old male with severe emphysema. While a suspected pulmonary arteriovenous malformation was identified in the left lung on plain computed tomography, contrast-enhanced imaging revealed an aneurysmal nodule connected to the left inferior phrenic and internal mammary arteries, suggesting a systemic artery-to-pulmonary artery fistula. Selective angiography confirmed the diagnosis. The absence of pulmonary vein dilation on computed tomography is the key to differentiating a systemic artery-to-pulmonary artery fistula from a pulmonary arteriovenous malformation. Additionally, using contrast-enhanced computed tomography with both pulmonary artery and late phases helps prevent misdiagnosis of pulmonary embolism and may raise the suspicion of a systemic artery-to-pulmonary artery fistula.