Sounds like (from the Italian article) she had already had an unsuccessful (or attempted?) kidney transplant in 2014. The patient appears to have some sort of vascular as well as immunological issues (again, my broken translation from the Italian).

When the donor kidney isn't a blood-type match for the recipient, I believe you can do the transplant with a splenectomy and plasmapheresis to eliminate pools of immune cells and desensitize the immune response to the incompatibility, but I believe that splenectomy has largely been replaced by treatment with rituximab (antibody-drug that targets immune B cells). Perhaps the combination of congenital vascular issues plus incompatibility in this patient made the transplant + splenectomy approach preferable?