Relationship of renal implantation biopsies and acute rejection during the immediate posttransplantation period

Correlation of acute tubular injury in reperfusion biopsy with renal transplant outcomes

Acute tubular injury (ATI) is common at reperfusion, but its relationship to graft outcomes is unclear. Prior studies lack standardization of morphological assessments and included elements of acute and chronic tubular injury. This study aimed to evaluate the impact of ATI on graft outcomes. Reperfusion biopsies from 2004 to 2009 were retrospectively reviewed. ATI was assessed by a new standardized scoring system. We also assessed chronic injury (CI) by the Banff criteria. Outcomes evaluated included glomerular filtration rate (GFR) at 1 and 5 years and delayed graft function (DGF), acute rejection (AR), graft and patient survival. ATI did not correlate with DGF, AR, graft or overall survival. Mild-moderate ATI was not predictive of GFR post-transplant. Moderate-severe CI was associated with lower GFR at 5 years with a mean difference of -7.14 mL/min/1.73 m(2) (P=.04) and overall survival (HR 2.44, P=.01). Other predictors of graft function included donor age, DGF, and AR. Histologic criteria of ATI at implantation in the absence of donor demographics or clinical information do not provide sufficient predictability in outcomes after transplantation. On the other hand, histologic assessment of CI correlates with GFR and overall survival.

Assessment of kidney organ quality and prediction of outcome at time of transplantation

The critical importance of donor organ quality, i.e., number of surviving nephrons, ability to withstand injury, and capacity for repair in determining short- and long-term outcomes is becoming increasingly clear. This review provides an overview of studies to assess donor kidney quality and subsequent transplant outcomes based on clinical pathology and transcriptome-based variables available at time of transplantation. Prediction scores using clinical variables function when applied to large data sets but perform poorly for the individual patient. Histopathology findings in pre-implantation or post-reperfusion biopsies help to assess structural integrity of the donor kidney, provide information on pre-existing donor disease, and can serve as a baseline for tracking changes over time. However, more validated approaches of analysis and prospective studies are needed to reduce the number of discarded organs, improve allocation, and allow prediction of outcomes. Molecular profiling detects changes not seen by morphology or captured by clinical markers. In particular, molecular profiles provide a quantitative measurement of inflammatory burden or immune activation and reflect coordinated changes in pathways associated with injury and repair. However, description of transcriptome patterns is not an end in itself. The identification of predictive gene sets and the application to an individualized patient management needs the integration of clinical and pathology-based variables, as well as more objective reference markers of transplant function, post-transplant events, and long-term outcomes.

Can donor implantation renal biopsy predict long-term renal allograft outcome?

BACKGROUND

Donor kidney implantation biopsy (IB) is performed on a regular basis, particularly as part of clinical studies.

OBJECTIVE

To determine the utility of donor implantation renal biopsy to predict the long-term renal allograft outcome.

METHODS

A Medline search for studies in English was performed with the following key words: implantation biopsy, renal transplantation and long-term outcome.

RESULTS

Sixteen trials involving 8,122 kidney transplants were identified, of which 6 were prospective studies. The histological abnormalities were scored mainly by the Banff schema and the graft outcome was defined either by delineating the delta changes in the pathology score or glomerular filtration rate. Normal histology with a well-functioning renal allograft had a favorable outcome. The extent to which the baseline tubular atrophy, interstitial fibrosis, glomerulosclerosis and vascular changes had on the long-term outcome varied from one study to another.

CONCLUSION

Abnormal IB has a better chance of predicting early graft outcome. The review questions the current wisdom for routine IB on all donors. In some donor kidneys, a biopsy provides significant prognostic information, such as older donor kidney, those with history of hypertension, diabetes, cardiovascular disease, and kidneys with abnormal creatinine. Future research on IB is necessary to find a more useful method to predict the long-term transplant outcome.

Histological alterations in implant and one-year protocol biopsy specimens of renal allografts

BACKGROUND

The natural course of histological changes and their correlations with clinical parameters have not been studied in large numbers in renal allograft specimens. The aim of this study was to determine whether any histological alterations developed during the first posttransplantation year. Immunological and nonimmunological factors possibly associated with subsequent histopathological changes and development of chronic rejection were also assessed.

METHODS

We studied 102 cadaveric kidney allografts for which both implant and 1-year protocol biopsy specimens were available. The chronic allograft damage index (CADI) was used to quantify the extent of histological changes that developed during the first year.

RESULTS

Overall, an increase in histological alterations were seen during the first posttransplantation year, and the CADI increased significantly. The mean CADI was 0.7 in relation to implant biopsy samples and 2.9 in relation to 1-year biopsy samples (P<0.05). Although the degree of changes increased during the first posttransplantation year, they were seldom severe. Significant increases in incidences of interstitial inflammation and fibrosis, tubular atrophy, and basement-membrane thickening were seen. Vascular intimal proliferation and glomerular mesangial matrix increase and glomerular sclerosis were also noted. In contrast, anisometric vacuolization in the tubular epithelium decreased significantly in incidence during the first year. CADI values 1 year after transplantation were significantly affected by donor age, occurrence of acute rejection episodes, and prevalence of HLA-DR mismatches. CADIs were also significantly higher in grafts with decreased function.

CONCLUSIONS

Histopathological alterations increased in almost every graft, even well-functioning grafts, during the first year. The CADIs relating to alterations seen in cases of chronic rejection increased significantly and were strongly affected by both immunological and nonimmunological factors.