Histopathology & Direct immunofluorescence (DIF) - Renal Biopsy (LM+DIF)

Histopathology and Direct immunofluorescence test (Renal biopsy)

It is a test done on renal (kidney) biopsy sample in order to detect various renal diseases. This test includes light microscopic (LM) examination of renal tissue specimen in order to diagnose a particular disease (also called histopathology test). This test is done by a pathologist who examines tissue (also called specimen) obtained with the help of a procedure called biopsy. Biopsy is a procedure where a small tissue sample is taken from disease organ for microscopic examination. Thus medical diagnosis is formed by pathologist based on histopathology test done on renal biopsy specimen.

This test also includes another technique called direct immunofluorescence (DIF) test where specific proteins or antigens are detected on renal biopsy specimen with help of fluorescence microscope to confirm renal disease. These two procedures (histopathology and direct immunofluorescence test) help in rapid and reliable diagnosis of renal disease/renal failure

Why is Histopathology and Direct immunofluorescence test (Renal biopsy) prescribed?

The health care provider i.e. treating doctor may advise renal biopsy followed by above mentioned laboratory tests under many circumstances, few of which are enlisted here:

• Renal hematuria (blood in urine) in absence of infection (and other urological tests are within normal limits) with or without renal dysfunction. It may be in associated with significant proteinuria and hypertension
• significant proteinuria (protein in urine) of >1 gm/day
• Unexplained renal failure and/or rapidly progressive renal failure
• Assess chronic changes in setting of autoimmune disorders, diabetes, hypertension
• Assess changes in kidney transplant such as rejection, infection etc

These tests help to diagnose the renal disease, its severity, aggressiveness of the disease. It also helps to plan out the treatment and monitor the response to it.

The various renal diseases diagnosed with these tests are:

• Podocytopathy- Minimal change disease, focal and segmental glomerulosclerosis
• IgA nephropathy
• Membranous nephropathy
• Membranoproliferative glomerulonephritis
• Autoimmune related glomerulonephritis, such as lupus nephritis, mixed connective tissue diseases, rheumatoid arthritis etc.
• C3 glomerulopathy and dense deposit disease
• Infection related glomerulonephritis
• Crescentic glomerulonephritis- Anti GBM disease, ANCA related glomerulonephritis, Lupus nephritis
• Malignant and benign hypertension related nephrosclerosis
• Glomerular deposition related diseases
• Diabetic nephropathy
• Tubulo-interstitial nephritis
• Transplant related changes, includes rejection, infection, drug induced changes, denovo and recurrent glomerular diseases.

What are the components of Histopathology and Direct immunofluorescence test (Renal biopsy) test?

This test includes light microscopy on sections cut from renal biopsy, stained with routine and special stains. Haematoxylin and eosin (routinely used stain) along with special stains like Jones methenamine silver, PAS and Masson trichrome are regularly used on kidney biopsy. A set of 8 slides in total is prepared, with almost 32 sections of biopsy being studied (4 sections per slide). A full panel of immunofluorescence staining with IgG, IgA, IgM, C3, C1q, Kappa and lambda antibodies are performed, analysing the glomerular, tubulointerstitial and vascular compartments.

Precautions of handling renal biopsy

• Ideally, 2 containers- one with tissue in formalin and other with tissue in Michell’s medium are required to adequately evaluate the Renal biopsy specimen.
• Many cases require Electron microscopic studies, like in cases of nephrotic syndrome to confirm podocytopathy, thin basement membrane disease in cases of unexplained hematuria, Alport’s syndrome in cases of sensorineural deafness, glomerular deposition diseases to ascertain the microstructure of deposits. In these cases, separate tissue in glutaraldehyde is preferred in addition to tissue for LM and IF.
• Tissue taken for histopathological examination should be handled with utmost care and precautions without destroying it by various instruments. Pulling of the tissue/ tissue fiddling should not be done.
• Tissue should not be put on dry gauze or gauze soaked with water.
• It should be immediately stored in an appropriate sized container containing 10% neutral buffered formalin (formaldehyde solution). The specimen should be totally immersed in formalin.

• It should not be freezed or put in ice cold saline.
• Container should be labelled properly with necessary details and clinical history and sent to laboratory.
• The part of tissue for immunofluorescence is put in transport solution i.e. Michell’s transport medium and is untouched by formalin or any other fixative.
• If only one core is taken, the same is judiciously divided for IF and LM before putting tissue into formalin fixative.