Lupus nephritis and role of kidney biopsy

Giannico and Fogo

Kidney biopsy is essential in the management of lupus nephritis, particularly regarding decision to use cytotoxic agents. However,its role in predicting outcome is unclear.

• The latest update in histologic classification (International society of nephrology/Renal pathology society or ISN/RPS) results in improved reproducibility among renal pathologists. The difficulty persists when one is trying to decide whether the glomerular sclerotic lesion is the result of previous active lesions (endocapillary proliferation, crescents) or not. If it is, the biopsy would qualify as chronic proliferative type (class III or IV with C or chronic).

• Although earlier studies using WHO classification did not find histologic classification more useful than clinical data in predicting outcome, recent ones found it to be more useful when combined with clinical data. 
• ISN/RPS designates S and G to the proliferative class III and IV because early study indicated that segmental proliferative lesion (S) fared worse than global one (G). However, later studies did not find the difference between the two. It is likely that the definition of segmental lesion in the original study and in ISN/RPS classification is not the same.
• Activity and Chronicity indices predict response to treatment. However, their usefulness as prognostic indicators is unclear. Reproducibility also posts a problem.
• When patients with proliferative LN flared, the repeat biopsy usually showed persistent proliferative lesions. Class transformation was found more often in patients with non-proliferative LN as the first biopsies.
• ISN/RPS, like preceeding WHO classification, is based on glomerular lesion. Renal outcome is mostly predominated by tubulointerstitial fibrosis and vascular lesions such as thrombotic microangiopathy (TMA).
• There is a degree of discrepancy between urine findings and histology. Minimal urine abnormalities can be seen in LN III or IV. Other non LN diseases can superimposed on LN in which specific treatment is required.