Which statement about arteriovenous fistulas is true?

Which statement about arteriovenous fistulas is true?

• A. They increase capillary density
• B. They cause decreased venous return
• C. They are acquired only
• D. Abnormal direct connections between arteries and veins bypassing capillary beds

Answer: (D)

Arteriovenous fistulas are abnormal direct connections between an artery and a vein that bypass the capillary beds. This creates a low-resistance pathway for blood to flow from arterial to venous circulation, so much of the arterial blood shunts into the venous system instead of passing through the capillary network. That bypass reduces flow through capillaries and can raise venous return to the heart, potentially leading to a high‑output state if the fistula is large. They can be present congenitally or acquired (such as from trauma or procedures). So the true statement is that AV fistulas are abnormal direct connections between arteries and veins bypassing capillary beds. The other options don’t fit this physiology: they don’t increase capillary density, venous return is typically increased rather than decreased, and fistulas are not limited to being acquired—they can be congenital as well.

Arteriovenous fistulas are abnormal direct connections between an artery and a vein that bypass the capillary beds. This creates a low-resistance pathway for blood to flow from arterial to venous circulation, so much of the arterial blood shunts into the venous system instead of passing through the capillary network. That bypass reduces flow through capillaries and can raise venous return to the heart, potentially leading to a high‑output state if the fistula is large. They can be present congenitally or acquired (such as from trauma or procedures). So the true statement is that AV fistulas are abnormal direct connections between arteries and veins bypassing capillary beds. The other options don’t fit this physiology: they don’t increase capillary density, venous return is typically increased rather than decreased, and fistulas are not limited to being acquired—they can be congenital as well.