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    Kidney biopsy

    Background

    Renal biopsies are taken in a variety of situations; to identify lesions seen on imaging which may be cysts, benign and malignant tumours, to assess pre- or post-transplant status and to evaluate kidney disease such as glomerulonephritis.1-3

    This protocol includes renal core and wedge biopsy specimens.


    Record the patient identifying information and any clinical information supplied together with the specimen description as designated on the container. See overview page for more detail on identification principles.

    At this point it must be determined whether the biopsy is for investigation of a tumour or treatment of a medical kidney condition/transplant rejection as this will determine the pathway followed.

    • No
      • Non-routine fixation (not formalin), describe.
    • Yes
      • Special studies required, describe.
      • Ensure samples are taken prior to fixation.
        • Immunofluorescence, electron microscopy
        • Cytogenetics, flow cytometry, frozen storage
    • Not performed
    • Performed, describe type and result
      • Frozen section
      • Imprints
      • Other, describe

    See general information for more detail on specimen handling procedures.

    Inspect the specimen and dictate a macroscopic description.


    External Inspection

    Describe the following features of the specimen:1-4

    Procedure

    Record as stated by the clinician.

    • Other, specify
    • Kidney wedge biopsy
    • Kidney core biopsy

    Specimen integrity

    • Number of cores/wedges
    • If fragmented, number of pieces received

    Specimen size (mm)

    Core biopsy

    Measure the size of each core/fragment in two dimensions:

    • Length
    • Diameter

    Wedge biopsy

    Measure the size of each in three dimensions:

    • Length along free edge
    • Depth into kidney parenchyma (from free edge to apex of wedge)
    • Thickness (from one capsular surface to the other at the widest point)

    Colour

    • Yellow
    • Brown
    • White
    • Green

    Dissection

    If more than one core of tissue is submitted it may be worthwhile putting the specimens in separate cassettes to maximise the investigations that can be performed on the tissue.

    Biopsies are usually assessed under dissection microscope in a drop of normal saline.

    Glomeruli appear as small red spheres in the cortex. The medulla appears as linear stripes. 1,4 Small yellow balls of fat will also be present. 2

    Excellent illustrations are available in references 1 and 4.

    Guidelines for division of the specimen will vary with the type of biopsy, the clinical question being asked, the urgency of that question, and the approach to subsequent investigations taken in the individual laboratory.3

    Native biopsies usually need to be divided into three and submitted for light microscopy, immunofluorescence (IF) and electron microscopy (EM).1,4

    A useful diagram provided is in reference 4.

    In theory a minimum of one glomerulus per study is usually adequate for IF and EM  and the majority should be submitted for light microscopy.1 If the specimen is limited, division is guided by the clinical question and/or immunohistochemistry facilities of the individual laboratory.

    When minimal tissue is available, it may be possible to retrieve a few more glomeruli for EM by rinsing out the biopsy needle.1

    Renal transplant biopsies may not require electron microscopy and immunofluorescence unless glomerular disease is suspected. 3 However it is important not to transfer the entire specimen to formalin until exact requirements are established.

    It is best to dissect the tissue while it is fresh. The majority of the biopsy should be processed for light microscopy but check if samples are required for immunofluorescence and electron microscopy.3

    The size of segments for each process will be dependent on the overall size of the core but 3 mm for light microscopy, 3 mm for immunofluorescence & 1 mm for electron microscopy should suffice if there is cortex with at least one glomerulus present in each piece.1 Some medullary tissue for the demonstration of casts in immunofluorescence may be useful if possible.2

    One recommendation is to submit 50% of core tissue for light microscopy, 30% for immunofluorescence and 20% for electron microscopy. More tissue from wedge biopsies may be submitted for light microscopy (up to 75% of tissue).5

    Wooden sticks may be used (in preference to forceps) to gently lift the cores without crushing.2,4 Renal biopsies must be carefully handled with clean instruments and separated into different solutions without any cross-over contamination of fixatives.2,4

    Transfer one piece of tissue into each of the following:

    • Viral transport solution or freezing for immunofluorescence
    • Glutaraldehyde for electron microscopy
    • Formalin for light microscopy

    Internal Inspection

    Not required.


    Processing

    Transfer the tissue selected for routine processing directly into cassettes. Lens paper lining or similar is required to prevent loss of tissue during processing.

    The use of biopsy pads is not recommended for kidney biopsy specimens as the foam material may cause artefactual holes.1,4

    Ensure adequate fixation and process on appropriate short cycle. Microwave fixation may be of assistance in expediting urgent specimens.1,4

    Record details of each cassette.

    An illustrated block key similar to the one below may be useful.

    Block allocation key

    Cassette id
    Site
    No. of pieces
    A
    Kidney
     

     

    Acknowledgements


    References

    1. Furness PN. Acp. Best practice no 160. Renal biopsy specimens. J Clin Pathol 2000;53(6):433-438.
    2. Lester SC. Manual of Surgical Pathology, Saunders Elsevier, Philadelphia, 2010.
    3. Roberts I, Furness PN and Cook T. Tissue pathways for medical renal biopsies, The Royal College of Pathologists, London, 2013.
    4. Walker PD, Cavallo T and Bonsib SM. Practice guidelines for the renal biopsy. Mod Pathol 2004;17(12):1555-1563.
    5. Stirling JW, Curry A, Eyden B, (eds). Diagnostic Electron Microscopy: a practical guide to Interpretation and Technique. Chichester, UK: John Wiley & Sons Ltd, 2012.

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      25-Mar-2019
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