A percutaneous renal biopsy may be obtained for a number of reasons, including establishment of the exact diagnosis, as an aid to determine the nature of recommended therapy or to help decide when treatment is futile, and to ascertain the degree of active (ie, potentially reversible) and chronic (ie, irreversible) changes [1,2]. The degree of active or chronic changes helps determine prognosis and likelihood of response to treatment. In addition, kidney biopsy can be performed to help assess genetic diseases.
It is important to recognize that prognostication based upon renal pathology alone may be affected by the sample size (particularly in lesions that are focal in nature) and may not be very accurate in biopsies with few glomeruli (ie, ≤5). The findings in renal biopsy always need to be interpreted in the context of the clinical and laboratory features. Chronic changes (interstitial fibrosis and tubular atrophy), for example, are a sign of the magnitude and duration of prior injury.
The following topic review provides an overview of issues relating to percutaneous renal biopsy. Nonpercutaneous renal biopsy techniques are also discussed.
The routine evaluation of a percutaneous renal biopsy involves examination of the tissue under light, immunofluorescence (and immunoperoxidase in some laboratories ), and electron microscopy. Each component of the evaluation can provide important diagnostic information. (See appropriate topic reviews for discussions concerning pathologic findings in individual disorders.) The routine immunofluorescence examination of biopsy specimens should include (at a minimum) evaluation of IgG, IgM, IgA, C3, C1q, albumin, fibrin, and kappa and lambda immunoglobulin light chains. Special studies, including evaluation of serum amyloid A deposits, IgG subclasses (IgG1-4), and collagen chains (alpha 3.4 and 5) may be helpful in some cases where available. (See "Thin basement membrane nephropathy (benign familial hematuria)" and "Genetics, pathogenesis, and pathology of hereditary nephritis (Alport syndrome)".)
Justification for the routine application of electron microscopy comes largely from studies in the 1960s and 1970s, which showed that this technique provided substantive diagnostic information beyond that obtained from light microscopy in nearly 50 percent of cases. However, most of these studies were performed at a time when immunofluorescence microscopy was not widely available.