A rare case of a pulmonary arterio-venous malformation not requiring treatment is reported. An incidental peripheral right lower lobe intrapulmonary pulmonary arterio-venous malformation was identified on computed tomography. On catheter angiography, no pulmonary artery supply was identified. Systemic artery catheter arteriography identified systemic arterial supply from a conjoined inferior phrenic artery with pulmonary venous drainage to the left atrium. Due to this lung abnormality being a systemic arterial circulation to pulmonary venous circulation (left to left or circular) shunt, no treatment was indicated.