Arterio-Venous Fistula Surveillance Using Tomographic 3D Ultrasound

Abstract

Introduction: A well-functioning Arterio-Venous Fistula (AVF) is essential for haemodialysis. Despite regular Duplex Ultrasound (DUS), a significant number of AVF's fail within the first year. Tomographic 3D ultrasound (tUS) creates a 3D CT-like image of the AVF that can be interpreted by the Clinician. We compared DUS, tUS and fistulograms for the identification and estimation of flow-limiting stenosis. Methods: Patients with suspected AVF dysfunction at routine Transonic® surveillance, meeting certain criteria, underwent DUS. Criteria for DUE were; 1) >15% reduction in access flows on two consecutive occasions, 2) >30% reduction in access flow on one occasion, 3) access flow of < 600ml, 4) presence of recirculation. On the day of fistulography, DUS was repeated, in addition to tUS imaging of the fistula including the stenosis. Delayed tUS measurements were performed by a Vascular Scientist blinded to the fistulography result, reported by one Consultant Radiologist, and the DUS. Maximum diameter reduction at any stenosis was measured using all three techniques. Observer agreement was also measured. Results: In forty patients with thirty two stenoses, mean (sd) stenosis was measured as 61.9(±16.6)%, 66.9(±9.51)% and 67.1(±11.9)% for the fistulograms, tUS and DUS respectively. tUS observer agreement was excellent [intra ICC = 0.94 (95%CI 0.86-0.97) and inter ICC = 0.87 (95%CI 0.72-0.94), p< 0.001]. Bland-Altman agreement for tUS was -5.1(±17.9)% (95%CI -40.2-30.1) compared with -5.2(±17.3)% (95%CI -39.1-28.6) for DUS with the fistulogram as the index standard. Mean (sd) tUS scan time was 3.7(±2.2) min, compared to 9.9(±3.7) min for duplex, p< 0.001. Conclusion: DUS and tUS were equally accurate at detecting complications compared to fistulography. tUS has excellent observer agreement, takes less skill and is significantly quicker than DUS in detecting stenoses in an AVF. There is a risk reduction for repetitive strain injury when people use tUS for AVF surveillance compared with DUS due to the shorter scan time. Disclosure: This work is funded by the European Commissions Horizon 2020 scheme.