Material/Methods: 74 cases of TMA were identified from the histopathology database of Department of Transplantation Medicine and Nephrology in  Warsaw (Poland). Archived renal biopsy specimen and accompanying medical records for each patient were obtained and reviewed. Patients were divided into 2 groups: A (n=32) who developed HUS until 1 month post-transplant and B (n=42) who developed TMA later. Data extracted from each clinical record included: HLA histocompatibility, CIT,treatment of HUS/TMA, infections, type of immunosuppressant drugs. Data extracted from biopsy specimen included: presence of C4D deposits, PTC infl ammatory infiltrates, necrosis of vascular wall, presence of clotting, tubulitis, chronic vascular, glomerular and interstitial changes and interstitial inflammatory infiltrates. Cox Model was used and HR was estimated. End point was time of returning on haemodialysis.
Results: Patients from group A became dialysis dependent later compared to group B (observation time 108 months, HR=0.33; p<0.001). After 70 months of
observation 73% of patients from group B returned on dialysis and 33 % of
group  A. Risk factors of returning on dialysis despite the time of developing HUS/TMA were: presence of clotting (HR=3.076; p<0.01), necrosis of vascular wall (HR 3.921; p<0.0359), tubulitis (HR 2,.373; p<0.0492), PTC inflammatory infiltrates (HR 5.467; p<0.0273). No correlation with C4D deposits was found.
Conclusions: Negative prognostic factors might be connected with coexistence of acute interstitial and/or vascular rejection in a renal biopsy specimen. It can be assumed that histopathology findings usually considered associated with acute rejection should prompt additional clinical management. On the other hand C4D deposits seem not to be sufficient to unequivocally diagnose acute rejection as factor C4D did not differentiate our patients. Further investigation is mandatory.

Keywords: Kidney Transplantation