What structure is typically not involved in a congenital AVF?

A congenital arteriovenous fistula (AVF) typically refers to an abnormal connection that develops between an artery and a vein due to developmental anomalies. In congenital cases, the connections are often more complex rather than a simple, single connection. The presence of a single connection would be more indicative of a simpler, potentially traumatic fistula or a surgical creation of an AVF for medical purposes (such as for hemodialysis). In contrast, congenital AVFs usually present with multiple small channels or pathways that arise between the arterial and venous systems due to abnormal development during embryogenesis.

Therefore, the typical involvement of small channels from artery to vein and a multitude of arteriovenous channels aligns with the more complex nature of congenital malformations. In these congenital AVFs, the connection between the artery and vein can lead to a variety of hemodynamic changes and clinical presentations, thus supporting the idea that a single connection is not characteristic of congenital formations.