Single center experience of subclinical rejections and BK nephropathies by kidney allografts' surveillance biopsies.

Purpose: Acute rejection of the kidney allograft remains the most important factor affecting the long-term graft outcome and is a major predictor of development of chronic damage and graft loss. Several studies have shown that early detection and treatment of subclinical rejection episodes may be beneficial for the graft outcome. The role of protocol (surveillance) biopsies and the value of donor specific antibodies (DSA) monitoring are still debatable.

Methods: This is a prospective observational study involving seventeen kidney recipients transplanted in north-eastern part of Poland who underwent "zero", 3-month and 12-month allograft biopsies as well as DSA assessment.

Results: Histologic analysis of the biopsies showed subclinical acute cellular rejection in 17.6% of patients (two tubulointerstitial, one vascular) at 3-months post transplantation, and additional case of borderline rejection at the 12-month point. Moreover, two cases (11.8%) of polyomavirus BK nephropathy were diagnosed (one at 3 and one at 12 month point). None of the patients developed de novo DSA.

Conclusions: Our protocol biopsies allowed us to detect significant proportion of patients with subclinical, but histologically relevant acute cellular rejection and BK nephropathy. Early therapeutic intervention had beneficial effects in a 4-year follow up.