Changes

== Introduction ==

== Introduction ==

This is a peripheral connection between an artery and a vein . It can be caused by a penetrating trauma (e.g. venepuncture), neoplasia, a mass ligation of vessels during surgery, aneurysmal rupture or the erosion of vessels by infection.  

This is a peripheral connection between an artery and a vein . It can be caused by a penetrating trauma (e.g. venepuncture), neoplasia, a mass ligation of vessels during surgery, aneurysmal rupture or the erosion of vessels by infection.  

<br>

<br>

An arteriovenous anastomosis causes there to be a low resistance pathway for blood to flow form high pressure arterial circulation to the low pressure venous circulation, which promotes preferential flow through the fistula. The result of this is increased venous return, causing an increased cardiac output and therefore leading to significant volume overload on the heart. It can also cause inadequate perfusion of the area perfused by the artery.  

An arteriovenous anastomosis causes there to be a low resistance pathway for blood to flow from high pressure arterial circulation to the low pressure venous circulation, which promotes preferential flow through the fistula. The result of this is increased venous return, causing an increased cardiac output and therefore leading to significant volume overload on the heart. It can also cause inadequate perfusion of the area perfused by the artery.  

<br>

<br>

== Clinical Signs ==

== Clinical Signs ==

Signs may include the area to be warm and swollen. There may be a palpabral thrill and pulsation over the area and a continuous machinery murmour may be audible. The animal may exhibit the Branham sign , which is when the fistula is occluded it causes a sudden rise in systemic vascular resistance and a drop in heart rate.

The area affected is likely to be warm and swollen. There may be a palpabral thrill and pulsation over the area and a continuous machinery murmour may be audible. The animal may exhibit the Branham sign , which is when the fistula is occluded it causes a sudden rise in systemic vascular resistance and a drop in heart rate.

<br>

<br>

== Treatment and Control ==

== Treatment and Control ==

The preferred treatment option is surgical and involves surgical ligation of the vessels to and from the affected area, resulting in prevention of flow through the affected area. This does have a tendancy to recur if inadequate ligation of the vessels was performed.  If the anastomosis is very severe then radical surgery or amputation of the region may need to be performed.

The preferred treatment option is surgical and involves surgical ligation of the vessels to and from the affected area, resulting in prevention of flow through the fistula. This does have a tendency to recur if inadequate ligation of the vessels was performed.  If the anastomosis is very severe then radical surgery or amputation of the region may need to be performed.

<br>

<br>

== Prognosis ==

== Prognosis ==

Good if treated. Persistant flow can lead to high output heart failure.

Good if treated. Persistent flow can lead to high output [[:Category:Heart Failure|heart failure]].

<br>

<br>

[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:Cardiovascular_System_-_Vascular_Pathology]][[Category:Venous Pathology]][[Category:To_Do_-_Review]]

[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:Cardiovascular_System_-_Vascular_Pathology]][[Category:Venous Pathology]][[Category:Expert_Review]]