Ultrasound Evaluation of Dialysis Access Complications

Arteriovenous fistulas (AVF) and grafts (AVG) are two common modalities for hemodialysis access, AV fistulas and AV grafts are not without their problems, however, and as such have been described as both the lifeline as well as the “Achilles heel” of hemodialysis access.
An evaluation of a malfunctioning fistula or graft must encompass a comprehensive evaluation of the access in order to identify the problem. Duplex ultrasound can help identify the existence or location/etiology of a problem in a noninvasive fashion for someone suspected to have a malfunctioning AVF or AVG, before proceeding to invasive fistulography. The most common lesions are stenoses of the outflow vein or anastomotic lesions. The possibility of a central venous stenosis can also be suggested using duplex ultrasound. Pseudoaneurysms and aneurysms do not pose as severe a threat to fistula patency but can cause compressive or bleeding issues late and should be identified and noted on any duplex ultrasound study.
The most common mode of failure of a native AV fistula is outflow vein stenosis, followed by anastomotic stenosis. The most common mode of failure of an AV graft is neointimal hyperplasia at the venous anastomosis due to turbulent flow in the area. Hemodynamically significant anastomotic stenoses are identified based on velocity criteria. High-resolution sonography defines the severity of the stenosis based on different criteria. In many situations duplex ultrasound can be used as a first line tool to interrogate a malfunctioningAVF andtodirect further invasive diagnostics or therapy such as fistulography or surgical revision. Duplex can readily identify areas of outflow vein stenosis or problems with the arterial or venous anastomosis.