Histopathology of renal disease

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Diagnosis and clinical management of renal disease is often largely through biochemistry of blood and urine. However, sometimes clinical need, such as the rapid deterioration in acute renal failure, requires a biopsy in order to:	Establish a diagnosis or exclude other possibilities; ascertain the severity of the lesion (grade it); or ascertain the amount of irreversible scarring (necrosis/sclerosis; stage it).
What sharp implements may be used to take a renal biopsy?	A true cut needle or spring-loaded biopsy gun.
How is the patient anaesthetised and the appropriate spot on the kidney found when taking a renal biopsy?	Local anaesthetic is used around the flank region, and ultrasound guidance is used by the nephrologist to identify the appropriate biopsy site.
Before any staining of renal tissue taken can occur, what must be done/looked for?	In just saline, the tissue sample must be examined under a dissecting microscope to ensure that the renal cortex and glomeruli are present, otherwise the sample is useless.
Dividing the biopsy should be done within minutes of removal to avoid artefactual structural changes. How many samples is the original biopsy usually divided into?	Three: for light microscopy (5-6mm), for electron microscopy (1mm), and for immunohistochemistry/immunofluorescence (2-3mm). In theory, a single glomerulus is sufficient for each technique.
What injury is a common consequence of renal biopsy acquisition?	Perinephric haematoma is a common consequence.
What is a concern when transferring the renal tissue from the patient to the assistant (for cortex confirmation) by the doctor?	Maintenance of sterility.
For light microscopy examination of renal tissue, what does haematoxylin and eosin staining show?	It shows the cellular composition of the tissue but does not show many useful structures including the basement membrane, and will not identify amyloid protein is devastating to the glomerular basement membrane.
What does staining renal biopsy tissue with methenamine silver distinguish?	The glomerular basement membrane and connective tissue matrix. This is useful for identifying thickening, for instance. Sometimes a H&E stain is used as a counterstain to methenamine silver as it facilitates the examination of the relations between glomerular cells and matrix.
What is the Periodic Acid Schiff stain useful for distinguishing in a renal tissue biopsy?	Both the glomerular cells, and the basement membrane and connective tissues. Methenamine silver is superior for distinguishing the basement membrane, but the Periodic Acid Schiff stain is used frequently to delineate tubular basement membranes and identify tubulitis, a principal marker of acute rejection.
What might be the result of preparing too thick a section of glomeruli?	Increasing the apparent cellularity and erroneously diagnosing a proliferative disorder, or being unable to see a segmental disease pattern.
What is Congo Red useful for staining in renal tissue biopsies?	Amyloid protein. This stain is usually a wise precaution when there is heavy proteinuria and/or a systemic disease that predisposes to amyloid.
What is an elastin stain useful for showing in renal biopsy tissue?	The capillary changes if any vascular disease is suspected.
What were trichrome stains used to see in renal biopsy tissue that is now detected using immunohistochemical techniques?	To show immunoglobulin deposits and fibrin.
Does red staining with a Congo Red stain confirm the presence of amyloid?	No, but under polarised light, if amyloid is present, the dye will glow apple green.
What proportion of UK labs perform electron microscopy techniques on all renal biopsy samples?	~60%, some regard this as a luxury.
What are the benefits of performing electron microscopy as well as other histopathological techniques?	It can occasionally produce unexpected second diagnoses, or refine a diagnosis (e.g. finding mesangial electron dense deposits in membranous glomerulonephritis suggests that the glomerulonephritis is secondary e.g. to lupus, rather than idiopathic), and may detect unsuspected method failures such as false negative immunohistochemical results.
Immunohistochemistry uses antibodies to detect structures, usually immune structures. What might this include?	IgG, IgM, and IgA, as well as complement - usually C3 (the opsonin), as well as C4 and/or C1q to indicate classical pathway complement activation, and C5b-9 to indicate presence of membrane attack complex deposition. Fibrin may also be sought to detect fibroid necrosis in vessels and fibrin in crescents. Lastly, Ig light chains (kappa and lambda) may be sought in the diagnosis of myeloma, for example. Antibodies to viral proteins or amyloid proteins may also be applied.
Once the antibodies have been applied to the renal tissue, detection of complexes is usually by immunofluorescence or immunoperoxidase. What must be removed from the sample in order for the immuno tests to be completed?	Abundant plasma proteins lead to non-specific staining if not removed.
A structural change in the glomerular basement membrane or excessive matrix deposition is probably indicative of...	...nephrotic syndrome.
Glomerular damage due to proliferation of endothelial or mesangial cells is probably indicative of...	...nephritic syndrome.
Damage to the glomerular basement membrane AND cell proliferation, is probably indicative of...	...a mixed nephritic/nephrotic syndrome.
If damage to the glomeruli is rapid, features of ? will develop?	Acute renal failure.

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Histopathology of renal disease

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