Interpretation of renal biopsies in IgA nephropathy

The renal biopsy is essential for the diagnosis of IgA nephropathy. It should also be possible to derive important information from the biopsy about prognosis and likely response to treatment. Biopsy features that are associated with progression to end-stage renal disease are glomerulosclerosis and tubulointerstitial scarring, marked crescent formation and marked arteriolar hyalinosis. However, with our present classification systems the renal biopsy adds little over and above clinical features in predicting outcome. It may be possible to improve the predictive value of the renal biopsy by adopting the following recommendations in developing new classifications: (1) looking at the ability of the biopsy to predict changes in renal function in the short term after biopsy rather than prediction of progression to end stage renal disease; (2) examining subgroups of patients where the biopsy is likely to be most informative; (3) distinguishing the effects of reversible and irreversible changes particularly with regard to response to treatment; (4) ensuring uniformity of definitions between pathologists, and (5) paying attention to small lesions and considering including additional biopsy features. The most important role for the renal biopsy in the future is likely to be in predicting response to therapy rather than predicting progression to end-stage renal disease.