Pulmonary arteriovenous fistula is a condition in which an abnormal connection (fistula) develops between an artery and vein in the lungs. As a result, blood passes through the lungs without receiving enough oxygen.

Pulmonary arteriovenous fistulas are birth defects that result when the blood vessels of the lung do not develop normally.

Patients with Rendu-Osler-Weber disease (ROWD), also called hereditary hemorrhagic telangiectasis (HHT), frequently have abnormal blood vessel development at many sites in the body, including the lungs, brain, nasal passages, liver, and gastrointestinal organs. This condition is slightly more common in women than in men.

Many patients have no symptoms. Some patients have difficulty breathing, shortness of breath with exertion, difficulty exercising, or bloody sputum. Nosebleeds may occur in patients with HHT.

Other symptoms that may occur include blue skin (cyanosis), clubbing of the fingers (enlargement of the tips of the fingers), and a murmur heard with a stethoscope placed over the malformation.

The patient's blood oxygen level is low. There may be an abnormally high red blood cell count.

A chest x-ray usually shows the abnormal blood vessels. A chest CT scan confirms the diagnosis.

A pulmonary arteriogram (motion picture x-rays taken after the injection of dye) is used to make a "road map" of the abnormal blood vessels before surgery or other treatments.