Should we ligate haemodialysis fistulas in patients once they have been transplanted successfully: a randomised feasibility study for a parallel randomised controlled trial

For millions of people around the world, a kidney transplant offers a second chance at life, freeing them from the grueling schedule of dialysis and restoring a sense of normalcy. Yet, even after a successful transplant, these patients face a hidden challenge that begins long before the surgery. To survive while waiting for a new kidney, most patients require a special connection between an artery and a vein, usually in the arm, known as an arteriovenous fistula. This connection acts as a superhighway for blood, allowing doctors to draw large amounts of blood quickly for dialysis. While this is the gold standard for dialysis, the connection forces the heart to work much harder than usual, pumping extra blood through the low-resistance pathway. Over years, this constant extra workload can strain the heart, potentially leading to enlargement or failure.

The medical question that has long divided doctors is what to do with this vital connection once the new kidney is working. Should the fistula be left alone, just in case the transplant fails and dialysis is needed again? Or should it be surgically closed to relieve the heart of its extra burden? While closing the fistula has been shown to reduce the physical size of the heart in some studies, it remained unclear whether this actually improved how patients felt, how well they could move, or their overall quality of life. To answer this, researchers across the United Kingdom designed a study to test whether a larger, definitive trial could even be conducted, and to see if closing the fistula offered any immediate benefits to the patients' physical health.

The researchers set out to test the waters with a smaller, preliminary study involving forty adult kidney transplant recipients who had stable kidney function and a working fistula. The goal was not to prove a cure, but to see if patients and doctors would agree to a major surgery versus a "wait and see" approach in a controlled setting. The team recruited participants from six different hospitals. Once enrolled, each person underwent a series of detailed assessments. They wore a wrist monitor for a week to track their daily movement, filled out questionnaires about their energy and daily activities, and underwent a rigorous exercise test on a stationary bike to measure their maximum oxygen intake. They also provided blood samples to check for a specific protein that rises when the heart is under stress.

The participants were then randomly assigned to one of two paths. Half were told to keep their fistula exactly as it was, receiving standard care unless a medical emergency forced a change. The other half were scheduled to have their fistula surgically disconnected. This procedure involved cutting the vein where it joined the artery and sewing it shut, a relatively straightforward day-case operation. The researchers planned to repeat all the tests—exercise, movement tracking, and blood work—six months later to see if the group that had surgery showed improvements in heart health and physical ability compared to the group that kept their fistula.

The study revealed a significant hurdle before it could even begin to answer the main medical question. While the team successfully recruited the target number of forty people, the plan to keep everyone in the study fell apart. Only twenty-seven of the forty participants, or about sixty-eight percent, completed the full six-month process. The biggest drop-off happened in the group scheduled for surgery. Of the twenty people assigned to have their fistula closed, seven decided not to go through with the operation as the date approached. This high rate of people changing their minds meant the study could not proceed to the larger, definitive trial it was meant to launch. The researchers had set a rule that at least seventy-five percent of participants needed to finish the study to justify a bigger effort, and this threshold was missed.

Despite the recruitment challenges, the data that was collected offered some intriguing, though tentative, clues. The primary measure of physical fitness, which is the maximum amount of oxygen a person can use during intense exercise, did not improve in the surgery group. In fact, the group that kept their fistula saw a slight decline in this measure, while the surgery group remained stable, but there was no clear jump in fitness for those who had the operation. Similarly, the wrist monitors showed that the amount of daily activity did not change significantly for either group.

However, other signs pointed in a different direction. The blood tests showed a notable trend: the levels of the heart-stress protein dropped in the group that had their fistula closed, suggesting their hearts were under less strain. At the same time, the patients who had surgery reported feeling physically stronger and more capable in their daily lives compared to those who did not. These improvements in how patients felt and the reduction in heart stress markers were observed in the small group that completed the study, but the numbers were too small to say for certain that the surgery caused these changes.

The study also shed light on why the larger trial was so difficult to run. Through interviews with patients and doctors, the researchers found that many people held strong, pre-existing opinions about their fistulas. Patients often felt a deep sense of security in keeping the connection, fearing that removing it would leave them vulnerable if the new kidney failed. Doctors, too, often had strong preferences for one approach over the other, making it hard to remain neutral when talking to patients. This lack of uncertainty, or "equipoise," made it nearly impossible to recruit enough people who were willing to let chance decide their treatment. Furthermore, the physical demands of the exercise tests proved difficult for many, with a significant number of participants unable to push themselves to the maximum effort required for the test to be valid.

Ultimately, the study concluded that while closing the fistula might offer some benefits to heart health and how patients feel, the path to proving this through a large-scale, randomized trial is blocked by practical realities. The reluctance of patients to undergo surgery and the difficulty in keeping them in the study mean that a traditional trial of this nature is likely unfeasible. The researchers suggest that if the medical community wants to settle this question, they will need to rethink the study design entirely, perhaps looking for different ways to gather evidence that do not rely on patients agreeing to a major surgery versus no surgery in a random assignment. For now, the decision to close a fistula remains a complex choice between the safety of a backup plan and the potential relief for a tired heart, with no definitive answer yet available.