Arteriovenous Fistula

Introduction

As the name implies, an arteriovenous fistula is an abnormal direct connection between an artery and a vein. This connection causes the capillary circulation to be completely ignored. We will concentrate on peripheral fistulas here. The consequences of an arteriovenous fistula are the following; Increased blood return to the right heart raises cardiac output, there is decreased blood perfusion at the affected site and venous hypertension will arise.

Some causes of an arteriovenous fistula include trauma, surgery and neoplasia amongst others.

Clinical Signs

Signs depend on where the AV fistula has formed. Some signs include subcutaneous oedema, presence of a warm swelling, inflammation, pain, palpable vibration (thrill) over fistula, increased pulse & heart rate, an auudible continuous murmur over the fistula site and the Branham sign (decreased heart rate with surgical occlusion of blood flow to fistula).

Diagnosis

Clinical signs and history are quite indicative of the condition.

Angiography can be performed and an abnormal direct connection between an artery and a vein will be found. Ultrasonography can also be used to demonstrate the presence of abnormal flow. 

Treatment and Control

Treatment is to surgically ligate the abnormal vessels to and from the fistula area. Another possible procedure would be amputation of the limb in severe cases.

Prognosis

Good with complete ligation and cessation of blood flow through the fistula. Poor if surgical ligation is unsuccessful at stopping blood flow through the fistula.

References

Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company
Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2)W.B. Saunders Company
Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier