Final answer:
In an AV fistula, substances can exit the bloodstream through the skin surrounding the fistula.
Step-by-step explanation:
An AV fistula is a connection between an artery and a vein, typically created for dialysis treatment in patients with kidney failure. In an AV fistula, blood is withdrawn from the body through the artery, flows through the dialysis machine to remove waste products, and then returns to the body through the vein. As the blood flows through the AV fistula, nutrients, waste products, and other substances that need to be removed from the body can exit the bloodstream through the skin surrounding the fistula.