LAUSR

DOI: 10.1111/iju.14576 The emergence of new, potent immunosuppressive agents has led to excellent graft survival after kidney transplantation. Most patients who receive a kidney allograft have an AVF that is used for hemodialysis therapy. An AVF for dialysis therapy is no longer required in most cases with a good functioning graft. Furthermore, AVFs might lead to serious complications, such as aneurysms, severely dilated veins, local pain, infection and adverse hyperdynamic effects on cardiac function. Recent studies reported the potential harm of a functional AVF even after renal transplant in terms of these complications. Therefore, surgical closure should be considered for patients with stable allograft function. In contrast, AVFs were spontaneously closed after kidney transplantation in some recipients, even though their AVFs were not used after kidney transplantation. These recipients do not require surgical closure of AVFs. However, the patency-time curve of functional AVFs after a kidney transplant has not previously been evaluated. In this study, we evaluated the natural history of AVFs in renal transplant patients and discussed the timing of surgical closure of AVFs. This study included 144 kidney allograft recipients who had AVFs. Clinical and laboratory information was obtained from electronic databases and medical records. All patients had been on hemodialysis before kidney transplantation. After kidney transplantation, they were maintained on two or three immunosuppressive medications including prednisolone, mycophenolate mofetil and tacrolimus. All patients had a well-functioning kidney, because we excluded the patients who had experienced graft loss and, as a result, required further hemodialysis. The significance of differences between the two groups was analyzed using the v-test (categorical values) and unpaired Student’s t-test (distributed variables). We censored patients who underwent surgical closure of AVFs at the time of operation. The rate of spontaneous closure of AVFs after renal transplantation was computed using Kaplan–Meier survival analysis. The characteristics of the study population are shown in Table S1. This cohort consisted of 79 men and 65 women with an average age of 45.0 years (range 16–69 years). The mean dialysis duration was 80.0 months (range 1–360 months), and the mean follow up was 44.3 months (range 0–289 months) after kidney transplantation. Among these patients, 106 (73.6%) received a living relative donor allograft and 38 (26.4%) received a deceased-donor allograft. Spontaneous closure of AVF was observed in 50 patients (34.7%) during the follow-up periods. Of these recipients, eight had experienced an AVF thrombosis during their hospital stay after kidney transplantation. There was no statistically significant difference in terms of dialysis duration or site of AVFs between the patients with spontaneous closed AVF and left-open AVF. The patency rates of the AVFs at 1, 2, 5 and 10 years post-transplantation were 80.9%, 73.9%, 60.9% and 52.4%, respectively. The functioning AVF ratio shows a plateau 7 years after kidney transplantation (Fig. 1). Currently, there are no guidelines or randomized studies for appropriate management of AVFs in patients with successful kidney transplantation. There are also no clinical surveys for the patency curve of spontaneous closure after kidney transplantation. Although a few studies reported that thrombosis of the AVF occurred in approximately 30% of kidney transplant recipients with functioning allografts, these studies did not mention the time point of thrombosis. In the present study, 36% of the patients experienced spontaneous closure at a constant rate within 2 years of the transplant; however, the rate of spontaneous closure gradually flattened between 2 and 5 years after transplantation. Approximately half of the patients still had a functional AVF after 5 years. A recent study showed that allograft histological findings of the protocol biopsy 2 years post-transplant are related to long-term graft survival. We followed the kidney transplant recipients at our institution and carried out a protocol allograft biopsy annually. Therefore, we recommend surgical closure of AVFs in patients with good allograft function and favorable histology from 2 years after kidney transplantation. Although a randomized control study is required to determine whether surgical closure for patients with asymptomatic AVFs is acceptable, it is acceptable to carry out AVF closure in patients with successful kidney transplants to prevent the potential harm of AVFs. This study was approved by the Ethical Review Board of Hokkaido University Hospital (ID: 020-0131) and was carried out in accordance with the Helsinki Declaration.