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.

A small number of patients who have no symptoms may need no specific treatment. For most patients with either single or multiple fistulas, the treatment of choice is surgery to remove the abnormal vessels and the adjacent lung tissue.

For some patients, it may be possible to block the fistula at the time of arteriogram.

The outlook for patients with HHT is less favorable than for those without HHT. The result of surgery to remove the abnormal vessels is usually good, and recurrence is unlikely.

Recurrence is possible if the treatment is to block the fistula (embolization).

The most worrisome complication for patients with untreated pulmonary arteriovenous fistulas is "paradoxical embolism" -- where a blood clot travels from the lungs to the arms, legs, or brain (if it travels to the brain, it can produce a stroke). Major complications after treatment for this condition are unusual.

Patients with frequent nosebleeds or difficulty breathing, especially if there is also a history of HHT, should consult their physician.

Because this condition is congenital (present at birth), prevention is not usually possible.