Chronic renal transplant rejection.

The most common cause of renal allograft failure, after the first year posttransplant, is chronic rejection (CR). The impact on allograft loss of CR has remained constant despite the improvements in immunosuppression that have occurred. This process is characterized by a gradual decline in graft function over months to years. Proliferation of vascular smooth muscle cells and fibrosis of the large arteries are the main pathologic characteristics of CR. The clinical course varies widely among patients, from stable function for years to graft failure within several months. The precipitating factors of CR may be many and are unknown. Chronic rejection is likely to be, at least in part, immune mediated. A history of acute rejection episodes correlates strongly with the development of CR. No method has been clearly shown to prevent or treat CR.