congenital pulmonary arteriovenous fistula, a direct connection between the arterial and venous systems of the lung present at birth that results in a right-to-left shunt and permits unoxygenated blood to enter the systemic circulation. The anomaly is probably caused by faulty development of the network of vessels covering the embryonic lungs. It is often accompanied by hereditary hemorrhagic telangiectasis (Rendu-Osler-Weber disease). The fistula may be single or multiple and may occur in any part of the lung. If it is in an accessible site, surgical correction is the method of treatment.
