In a patient with chronic kidney disease who has an arteriovenous fistula in the left forearm, which observation most suggests the fistula is patent?

• A. Palpation of a thrill
• B. Auscultation of a thrill
• C. Absence of bruit
• D. Pain at the fistula site

Answer: (B)

The key idea is that a functioning arteriovenous fistula produces turbulent, high-velocity blood flow, which creates signs you can detect on exam. Two classic indicators of patency are a thrill and a bruit: a thrill is the vibrating sensation you feel over the fistula from the rapid flow, and a bruit is the whooshing sound heard with a stethoscope as blood moves through the fistula. When you auscultate and hear that turbulent-flow sound, it points to ongoing flow through the fistula, meaning it’s patent. In contrast, the absence of either sign raises concern for thrombosis or stenosis, and pain at the fistula site suggests a complication rather than normal patency. So detecting a turbulent flow through auscultation aligns with the idea that the fistula is open and functioning.