The Role of Immunosuppressive Therapy in Aneurysmal Degeneration of Hemodialysis Fistulas in Renal Transplant Patients

Background: Venous aneurysms are long-term complications of arteriovenous fistula (AVF) for hemodialysis with an estimated incidence rate of around 5–6%. The purpose of our study is to investigate the role of immunosuppressive therapy in the development of AVF aneurysms in renal transplant patients, and to determine whether AVF closure following transplantation is necessary. Methods: Forty-six patients with symptomatic venous AVF aneurysms underwent ligation and resection of their fistulas between January 2013 and January 2020. Immunohistochemical expression of CD3, CD4, and CD8 was assessed on the surgical specimens to characterize lymphocytic infiltrate in the aneurysm wall. Patients were subdivided into “Group A”—kidney transplant patients undergoing immunosuppressive therapy which was comprised of 39 patients and “Group B”—patients who had not undergone kidney transplant which was comprised of 7 patients. The 2 groups did not significantly differ in age, sex nor risk factors for aneurysms. Results: Group A showed a significantly higher aneurysm diameter (P < 0.0001), mean flow (P < 0.0001) and required a longer duration of surgery (P = 0.0007). A CD3+ lymphocytic infiltrate was significantly more common in Group A than in the Group B (90% vs 29%; P < 0.001). No significant differences in localization (adventitia, media or intima) and type (CD4+ vs CD8+) of lymphocytes were found between the 2 groups. Conclusion: AVF venous aneurysms were significantly larger and with a more intense T-lymphocytic infiltrate in patients undergoing immunosuppressive therapy. This finding suggests that immunosuppressive therapy plays a role in aneurysm formation, supporting the need for AVF closure in patients with an estimated low risk of rejection.