The Use of Ultrasonography in the Creation and Maintenance of Hemodialysis Arteriovenous Fistulas and Grafts Pictorial review

This pictorial review aims to explore the utility of ultrasonography (US) in the evaluation of vascular access (VA: AVF/AVG/percutaneous AVF) and demonstrate its ability to accurately screen for primary or delayed complications.  After this review, participants should be able to appropriately identify patients who could benefit from invasive angiographies.

Background:

Obtaining a viable VA is a crucial step in the process of Hemodialysis (HD). US of the VA offers a fast and noninvasive means for evaluating patients with issues detected either by physical examination or dysfunction during HD sessions. US should include real time imaging of the inflow artery, outflow vein, needle access site, vein wall depth from the skin and the identification of possible complications mentioned.

Clinical Findings/Procedure Details:

Stenosis: Grayscale, color, and spectral doppler US are used for diagnosis of vessel stenosis. Grayscale imaging is performed to detect any measurable decrease in luminal diameter (1). Peak systolic velocity (PSV) ratio (anastomosis/artery 2 cm upstream) greater than 3:1 suggests a stenosis, if associated with diameter reduction greater than 50% (2, 3). Elevated PSV at the anastomosis alone ( >375 cm/s) was shown to have a significant correlation with 50% stenosis in a study (4).

Maturation Failure: Draining vein US evaluation for large venous branches and for outflow stenosis, as described above, is performed to evaluate for causes of immaturity.

Thrombosis: A history of recent onset of access difficulty, a significant drop in blood flow ( >25% from baseline), or a new onset of lowered blood flow (< 500ml/min in AVG or < 300ml/min in AVF) may be clues to an impending VA thrombosis (5, 6). Measurement of dynamic venous pressure, measurement of access flow are noninvasive methods of measuring the blood flow in the VA.

Hemodialysis Steal: Duplex Doppler US is performed in symptomatic patients to detect flow reversal distal to VA and either low or high flow velocities, that is useful in planning treatment (7). 

Aneurysm/Pseudoaneurysm: Grey scale US imaging can detect outpouching arising from the main draining vein or graft, and turbulent flow within the outpouching producing a ‘yin-yang’/”to and fro” appearance will be seen on doppler imaging.

Conclusion and/or Teaching Points:

Ultrasonography plays an important role in the evaluation of VA and their associated complications. The widespread use of screening ultrasound can aid in the recognition of common complications and decrease the time required to receive appropriate therapeutic treatment.