Background: Early postoperative vascular ultrasound can predict the maturity of arteriovenous fistulas as well as detect complications.
 Objective: To present the characteristics of upper extremity vessels on ultrasound prior to AVF surgery and to analyze the changes in vessel size and flow rate postoperatively.
 Subjects and methods: We prospectively describe 80 cases of AVF formation at Dong Nai General Hospital from April 2022 to April 2023. Vascular ultrasound evaluations were conducted preoperatively and at 1 day, 2 weeks and 6 weeks postoperatively to evaluate the diameter and the blood flow of vessels used to create AVFs.
 Results: Eighty patients underwent AVF surgery. In forearm AVFs, the median diameter of the feeding artery and the draining vein were 2.12 (1.83 – 2.5) mm and 3.38 (2.9 – 3.80) mm, respectively. In upper-arm AVFs, the median diameter of the feeding artery and the draining vein were 3.67 (3.45 – 3.99) mm and 4.0 (3.64 – 4.05) mm, respectively. The draining vein flow rate showed a strong correlation with the brachial artery flow rate (R2 = 0.94, correlation coefficient = 0.88). The diameter and flow rate of the draining vein at 6 weeks post-surgery displayed significant correlations with their respective values at 2 weeks post-surgery, with correlation coefficients of 0.92 (R2 = 0.66) and 1.04 (R2 = 0.86), respectively. After 6 weeks post-surgery, non-diabetic patients exhibited larger draining vein diameters and higher flow rates compared with diabetic patients.
 Conclusions: The study highlighted the predictive potential of vascular ultrasound at the 2-week postoperative mark for AVF maturation The brachial artery flow rate can serve as a reliable indicator of AVF flow rate. Given the tendency for diabetic patients to exhibit smaller draining vein diameter and lower AVF flow rate than non-diabetic patients, particular caution is recommended when performing preoperative ultrasound mapping in this patient population.