The kidneys are required for excretion of excess fluid and harmful toxins. If a person develops kidney failure then build-up of toxins can be fatal within a few days. Consequently, patients with kidney failure require either a replacement kidney (kidney transplant) or for the excess fluid and toxins to be removed from the body by a process known as dialysis. There is a great shortage of kidneys for transplantation in the UK and many patients with kidney failure are not fit for such a large operation. Most patients who develop kidney failure will therefore need dialysis at some point.
Two-thirds of patients with kidney failure (around 20 000 patients a year in the UK) receive regular dialysis through a machine (haemodialysis). Attachment to the machine either requires the placement of semi-permanent ‘lines’ (plastic tubing) into one of the big veins in the patient’s chest, or the surgical creation of an ‘arterio-venous fistula’, in which one of the small arteries in the arm is joined directly toone of the veins. The vein becomes gradually bigger, such that the flow is increased substantially. Fistulas are the best option for most patients, as the risks of a life-threatening blood infection are about ten times less common than for patients who dialyse via their ‘line’.
Unfortunately, the creation of an arterio-venous fistula is not an exact science and up to half of them fail within a year of being created, despite a successful join at the time of surgery. The reasons why this happens and how we can prevent it are largely unknown, and our study will examine whether wecan use ‘doppler ultrasound’ (a non-invasive scan that uses high-frequency sound waves to create a picture of the blood flow in the fistula) to identify early problems with a fistula that may lead to it failing. We will then test whether we can then intervene in some way to save these failing fistulas.
To test whether ultrasound helps predict which fistulas will fail, we will recruit patients who are already on dialysis and who have a new fistula created. We will perform a series of scans in the first weeks after the operation (concealing the results from both the patients and clinicians). This should enable us to determine whether the scan helps to predict fistula failure and the best time to perform the scan after the operation. The second part of the study will test whether, having identified which fistulas are likely to fail, we can intervene and prevent this failure. The intervention is likely to be either‘fistulaplasty’ or ‘surgical correction’. In fistulaplasty, the fistula is punctured with a needle, and then a balloon is passed up to the narrowed segment of fistula and inflated to widen the narrowing. Surgical correction usually involves a small operation either to open up the narrowed segment or to create a new join that by-passes the narrowing.
There is still a great deal of debate about the role of ultrasound in improving the chances that a fistula will mature successfully. This is important because the use of ultrasound is expensive, but also means that patients have additional scans that are perhaps unnecessary. Our study, which will involve a number of large UK dialysis centres, will show once and for all just how effective or otherwise ultrasound is at helping fistulas to develop successfully, and whether this represents a good use of NHS funds. By doing so, we anticipate that our study will influence current dialysis practices here and abroad.