Importance of kidney biopsy in graft selection.

Pretransplantation biopsies of kidney grafts have become a key to select organs suitable for transplantation from marginal donors. The main microscopic features to be evaluated are as follows: percentage of glomerulosclerosis, interstitial fibrosis and vascular pathology. Although the percentage of glomerulosclerosis prognosticates kidney outcome, it has not yet been established what the age limit and type of kidney injury absolutely forbid the use of a particular organ. The principal reason for the controversy about the real value of the biopsy is due to the limited knowledge of the impact of age on the morphology of renal injuries. We reviewed 50 autopsies of patients older than 65 years, and 75 kidney biopsies showing renal disease. The percentage of glomerulosclerosis was always <15% in autopsy material, and <20% in kidney biopsies. We consider that improvement of the predictive value of pretransplantation renal biopsies may be achieved with the following guidelines: sufficient size of wedge biopsies (1.5 cm deep), not limited to the subcapsular area; never having <25 glomeruli; and a fast paraffin embedding technique that allows an objective evaluation of percentage of glomeruli and arterial-arteriolar damage. Transplantation is contraindicated when there is >20% of glomerulosclerosis accompanied by arteriolar damage.