Despite a significant improvement in the short term survival of kidney transplants, long-term allograft survival remains limited by Chronic Allograft Nephropathy (CAN). CAN may be due to several immunological and non-immunological factors. Two important causes of CAN are (1) subclinical rejection resulting from suboptimal immunosuppression and (2) chronic calcineurin inhibitor (CNI) toxicity. Protocol biopsies are an attractive tool for the detection of subclinical rejection and drug toxicity. The aim of this retrospective study was to evaluate the usefulness of protocol biopsies in the modern immunosuppressant era. From July 2001 to October 2003, 193 patients (pts.) received kidney transplants (ktx) in our centre. 53 pts underwent a protocol biopsy at 1, 6 and 12 months post transplant.

Patient Demographics

Age	Male	AA	Diabetics	CIT
50.4 ± 12.9	32 (60%)	9 (17%)	19 (36%)	18.1 ± 6.8

All pts received 3-5 doses of Thymoglobulin (average total dose 3.4 ± 1.2 mg/kg) and tacrolimus (TAC), mycophenolate mofetil (MMF) and steroids (250mg/iv POD 0 and 125 mg/iv POD 1, 30 mg/po POD2). Steroids were tapered to zero in 26 pts in one week. 27 pts continued prednisone 5 mg/day indefinitely. A total of 91 protocol biopsies were performed. One pt (1%) demonstrated grade 2A rejection at one month biopsy which was treated with steroid bolus therapy. Ten biopsies (10%) showed borderline rejection. Five biopsies (5%) revealed tacrolimus toxicity and one pt showed cholesterol emboli. At one month, 2 pts (5%) showed minimal fibrosis and 2 pts (5%) demonstrated mild fibrosis. At 6 months, 1 pt. (4%) had minimal fibrosis, 4 pts. (15%) showed mild and one pt. (4%) revealed moderate fibrosis. At one-year biopsies, only one pt with borderline subclinical rejection at 3 months biopsy, the amount of fibrosis increased from mild to moderate. In the rest of the biopsies the amount of fibrosis remained unchanged. When using thymoglobulin induction in combination with TAC and MMF with or without steroids, the rate of subclinical rejection is very rare (1%). Protocol biopsies in the modern immunosuppressant era may not be necessary to detect subclinical rejection. However, protocol biopsies may provide valuable information for monitoring fibrosis (CAN).