Health monitoring of fistulas for dialysis patients using ultrasound scans 1=Biomaterials and tissue engineering 2=Healthcare technologies

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Chronic kidney disease affects about 3 million people in the UK and currently over 30,000 people are on haemodialysis. Dialysis is the only option apart from a transplant for severe chronic kidney disease patients with reduced kidney function. To establish vascular access for dialysis, you need to create arteriovenous (AV) fistula. AV fistula is the surgical re-routing of a vein in the arm to an artery, bypassing small blood vessels (capillaries). After the fistula surgery, the vein undergoes dramatic changes over time: the wall of the vein is stretched and the vessel lumen increases to enable blood flow over 500 ml/minute. The vein becomes larger and stronger to allow easy access with needles for dialysis. At maturation, AV fistula provides a long-term access point to connect the patient to the dialysis machine. Unfortunately, AV fistula does not last forever. Its function can deteriorate over time, and it will ultimately fail at some point. The underlying causes for fistula failure are still not very well understood and the average time span for a new AV fistula is about 5 years. Unpredictability of whether the fistula will fail or not can cause high levels of anxiety among dialysis patients. For example, a fistula can develop stenosis and suddenly clot up. When a fistula no longer functions adequately, a new fistula has to be created surgically and this can have a detrimental impact on physical wellbeing and mental health of dialysis patients. In this project, we propose a novel health monitoring of fistulas using ultrasound scanning. We follow a small group of dialysis patients at Royal Berkshire Hospital (RBH). During their regular hospital visit for dialysis, patients will be scanned using ultrasound. Fistula health monitoring requires repeat medical scans of AV fistulas. The low risks associated with ultrasound scanning makes this approach possible. Otherwise, this would not be safe (in case of CT) nor economically feasible (in case of MRI). We cannot use a CT scanner for everyone due to health risks and cost. Handheld ultrasound technique producing a fistula model is a practical alternative to create individual 3D fistula imaging models. As fistula function is closely related to the blood flow dynamics of the fistula, computational fluid dynamics (CFD) simulations can help us understand the underlying haemodynamic characteristics in the fistula and thus monitor the fistula function. The 3D fistula models constructed from ultrasound scans will be used for CFD modelling in fistula patients. Patient-specific CFD modelling of fistula blood flow will inform us of early signs of fistula failure and also shed insights into the causes of these failures. By understanding the flow dynamics of fistula, we can predict which fistula is going to work. We can also identify fistulas which are more likely to develop stenosis because of their flow dynamics, and we may be able to keep them going longer through early intervention. This is an ambitious project to develop a reliable and practical technique for ultrasound image acquisition for CFD modelling in fistula patients and to establish a robust protocol which can be used in future longitudinal studies. We will work alongside an industry partner (Philips), leveraging their expertise on image acquisition. This project will lead to a better understanding on fistula health monitoring and early intervention. The data analysis will be streamlined, so that it becomes a clinical tool rather than having the data and waiting for several days before you have an answer.