Histopathology of a human allografted kidney with clinically sufficient function

To clarify the clinico-pathological significance of protocol biopsy and cli nically silent rejection in the management of renal graft recipients, we se lected a total of 139 (23%) from 604 biopsy specimens according to the foll owing criteria: 1) less than 1.4 mg/dL of serum creatinine and 2) more than 1500 mL/d of urine volume at time of biopsy. Clinical indications for the biopsy were classified into five categories: i) protocol biopsy (73 specime ns), including 69 cases at discharge post-transplantation; ii) slight incre ase in serum creatinine (32); iii) proteinuria (20); iv) evaluation of puls e-therapy (13); and v) fever elevation (1). Except for the last category, t he specimens were histopathologically diagnosed as being normal in 50 (68%) , 6 (17%), 1 (5%), and 5 (38%) specimens, respectively. Even borderline cha nges, and mild acute rejection, as well as drug-induced nephropathy were in cluded, implying the existence of clinically silent rejection or drug-induc ed nephropathy. Obvious diversity in the histopathological diagnosis was no ted in category iii) showing proteinuria, which was mainly caused by chroni c rejection, drug-induced nephropathy and glomerulonephritis. The graft sur vival rate was no different among the four categories, except for category v). These results indicate that biopsies obtained from functionally suffici ent renal grafts could provide useful information in the management of the recipients. The clinical significance of protocol biopsy awaits further cla rification by the analysis of a large number of cases.