Occasionally, patients may have isolated hematuria (i.e., without proteinuria or renal insufficiency). The differential diagnosis for such patients includes thin basement membrane disease, mild IgA nephropathy, and hereditary nephritis. A kidney biopsy is typically not performed, however, because treatment is not instituted unless there is significant proteinuria or renal insufficiency.

Renal transplant. Patients who have undergone renal transplant and subsequently develop renal failure should have a biopsy if their renal function does not improve after provision of intravenous fluids. In such circumstances, a biopsy is helpful for differentiating between various entities, such as acute or chronic rejection, drug toxicity (especially from calcineurin inhibitors), and BK virus infection. Some centers also routinely take biopsies from transplanted kidneys at predetermined time points, even in the absence of overt dysfunction because some renal disease may initially be clinically silent.