The most common cause of acquired aeriovenous fistula is?
**Core Concept**
Acquired arteriovenous fistulas (AVFs) are abnormal connections between arteries and veins, leading to an abnormal shunting of blood from high-pressure arterial to low-pressure venous systems. This can result in various complications, including heart failure, anemia, and high-output cardiac failure.
**Why the Correct Answer is Right**
The most common cause of acquired AVFs is iatrogenic injury, typically resulting from invasive procedures such as angiography, central venous catheterization, or vascular surgery. The creation of an AVF occurs when there is a direct puncture or laceration of an artery with a nearby vein, leading to a direct communication between the two. This can be due to the use of large-gauge needles or catheters, excessive force during insertion, or improper technique.
**Why Each Wrong Option is Incorrect**
**Option A:** Trauma is a possible cause of AVFs, but it is not the most common cause. Traumatic AVFs typically occur in the setting of severe injuries, such as those seen in motor vehicle accidents or explosions.
**Option B:** Infection is not a direct cause of AVFs. While infection can lead to local tissue damage and potentially create an environment conducive to AVF formation, it is not a primary cause.
**Option C:** Congenital AVFs are a distinct entity and are not considered acquired. They are present at birth and are often diagnosed incidentally or due to symptoms such as high-output heart failure or palpitations.
**Clinical Pearl / High-Yield Fact**
When performing invasive procedures, it is essential to use the smallest-gauge needles or catheters necessary and to employ proper technique to minimize the risk of iatrogenic AVF formation.
**Correct Answer:** C. Iatrogenic injury is the most common cause of acquired AVFs.