[Indications for renal biopsy].

The cost/benefit ratio of renal biopsy defines the mandatory indications in situations where histologic diagnosis is required for the choice of treatment and for predicting the evolution of renal function. These indications include nephrotic syndrome, permanent proteinuria associated with microhematuria or not, rapidly progressive nephropathies, and, at least in some authors' view, systemic lupus erythematosus. Additional indications should be considered in patients presenting with acute renal failure of unknown origin, renal involvement accompanying systemic diseases, isolated microhematuria and intermittent proteinuria. In these latter indications histology allows the choice of specific therapy in some 20% of cases; the evolution of renal function can be correctly evaluated in 90% of cases. Patients usually consider renal biopsy a benign investigation which helps them to cope with their disease on the basis of a definite diagnosis.