P1620PROGNOSTIC VALUE OF RENAL BIOPSY QUANTITATIVE HISTOLOGY IN LIVING KIDNEY DONORS AND RECIPIENTS OF KIDNEYS FROM LIVING DONORS

Background and Aims Living kidney donors (LKD) have an increased risk of chronic kidney disease. Likewise, renal transplant recipients may experience early or unexplained loss of graft function. We examined the predictive value of stereology based on a CT-scan and a biopsy from the transplanted kidney in relation to renal function outcome in both LKD and recipients of kidneys from living donors. Method A pre-transplantation contrast-enhanced CT-scan was used to obtain cortical volume of both kidneys using the Cavalieri estimator. Glomerular number density in a baseline biopsy from the transplanted kidney (taken at the time of transplantation) was estimated by a model-based method and multiplied with cortex volume to estimate the total number of glomeruli in the donated kidney. Glomerular volume was estimated by the 2D nucleator (1). In addition, kidney fibrosis (point-counting), glomerular sclerosis, and arteriole dimensions (2D nucleator) were also calculated. Pre-donation single kidney glomerular filtration rate (GFR) was determined using 51chrome EDTA clearance together with a renography and the GFR measurement was repeated one year after transplantation in both donors and recipients. We examined the association between GFR at one-year follow-up and cortex volume and various histology parameters from the baseline biopsy after adjustment of age, sex, body mass index, smoking status, 24-hour mean blood pressure and single-kidney GFR before transplantation. Results CT-scans, GFR measurements and kidney histology from 49 LKD and 38 recipients of kidneys from living donors were available for analysis. Mean age of donors was 50±12 years (55% women) and of recipients 46±13 years (26% women). In donors, GFR decreased from 113±24 to 71±16 ml/min while in recipients GFR was 61±18 ml/min at one-year follow-up (all with a functioning graft). In donors, GFR at follow-up of the remaining kidney had increased by 28% as compared to baseline. Follow-up GFR correlated to cortex volume (P<0.001), but not to any of the histological parameters (total glomerular number, glomerular volume, % sclerosed glomeruli, % kidney fibrosis or arteriolar dimensions). In recipients, GFR at follow-up had increased by 8% as compared to single-kidney GFR before donation. Follow-up GFR correlated to % kidney fibrosis (P=0.02) and % sclerosed glomeruli (P=0.05), but not any of the other histological parameters or cortex volume. Conclusion When adjusted for relevant clinical confounders the estimation of cortex volume had predictive value for renal function outcome in LKD while % kidney fibrosis and % sclerosed glomeruli had predictive value in recipients of kidneys from living donors.