Background: Many factors affect long-term results in kidney transplantation including histologic damage as a independent predictor, eg, chronic allograft dysfunction (CAD) in protocol biopsies and age-dependent lesions. Histopathologic findings correlate with the incidence of delayed graft function, eventual renal function, and allograft survival, allowing a rather precise prediction of graft outcomes.
Patients and methods: We analyzed 92 thick-needle preimplantation renal biopsies and 29 from grafts after explantation. They had been preserved in 4% formalin and immersed in paraffin. Evaluable specimens contained ≥10 glomeruli and ≥2 arterial cross-sections. We analyzed tubulitis, intensity of acute tubular necrosis (ATN), inflammatory infiltration, glomerulonephritis, arterial hyalinization, arteritis, fibrosis, tubular atrophy, arterial intimal fibrosis, increased mesangial matrix, and glomerulosclerosis percentage, although for comparative analysis not only optimal ones were taken into consideration. Over postoperative time, we analyzed patient condition, urine output, serum concentrations of creatinine, urea, uric acid, and ions as well as necessity for postoperative dialysis, ie, delayed graft function (DGF). During the 3-year observation we analyzed living recipients, graft loss, death with a functioning graft, incidence of dysfunction (CAD), and acute rejection episodes (ARE).
Results: We observed significant correlations between immediate graft function (IGF) and lack of ATN in the pretransplantation biopsy. The presence of ATN significantly correlated with DGF and primary graft non-function. There was no correlation between renal function and arterial hyalinization or fibrosis, inflammatory infiltration, and tubular atrophy. Over postoperative time we observed significant correlations between IGF and the lack of interstitial fibrosis as well as significantly lower levels of creatinine, urea, and potassium as well as greater urine output early after transplantation. IGF correlated with shorter time to reach a creatinine level of 2 mg/dL, lower concentrations of creatinine, urea, and potassium, as well as greater diuresis during the first 5 days. In addition, lower creatinine and urea concentrations after 1 month and of urea at 6 and 36 months were associated with IGF. Female recipients showed lower concentration of creatinine over 3 months, of urea during the 1st day, and of potassium at 1 month; however, thereafter the differences were not significant. Better function of the right kidney was observed. The presence of severe ATN (ATN III) correlated with lower creatinine concentrations at 6 months and urea after 3 years. The presence of hyalinization in biopsies correlated with higher concentrations of urea at 1 year and of borderline significance after 3 years; surprisingly, potassium concentrations were lower after 2 and 3 years. The presence of inflammatory infiltrates correlated with higher creatinine concentrations after 1 and 3 years; similar correlations, albeit of borderline significance, were observed in tubular atrophy. Interstitial fibrosis correlated with creatinine concentrations during 10 days after the operation and after 12 months, also with potassium concentrations 5 days after the operation. Borderline correlations were observed between donor age and creatinine concentration in the first day after the operation, after 6 months, and time to achieve a creatinine concentration of 2 mg/dL. We observed that biopsies with greater numbers of glomeruli correlated with better graft function, namely, lower creatinine concentrations after 5 days as well as at 1 and 6 months, as well as lower urea concentrations after 5 days and 6 months. We also observed differences in renal function depending on gender. The presence of acute tubular necrosis, arterial fibrosis and a lack of inflammatory infiltration in pretransplantation biopsy correlated with worse late renal function. Explantation biopsies showed signs of CAD in 66.4% and histologic features of ARE in 38.51%.
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