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made from the information obtained through renal biopsy.
The renal biopsy procedure requires expertise and should be performed only by experienced personnel. Hypertension and coagulation disorders should
be controlled prior to biopsy. Moderate to severe thrombocytopenia, uncontrolled systemic hypertension, administration of a NSAID within the previous 5 days and operator inexperience may all increase the risk of
An Urban Experience
post-procedural hemorrhage. Other contraindications to biopsy include renal cystic disease, moderate to severe hydronephrosis, pyelonephritis, perirenal abscess, severe anemia, and pregnancy. A relative contraindication to renal biopsy is the lack of access to a qualified and experienced renal diagnostic pathology center.
Renal biopsy samples can be obtained by one of several techniques:
   Percutaneous
   Ultrasound guidance - Preferred method for dogs >5 kg and all cats
   Blind or palpation technique - Better suited for cats; rarely performed in dogs
   Keyhole technique - Used in dogs when ultrasound guidance not available
   Laparoscopy - Requires specialized equipment and expertise; preferred method of some clinicians
   Surgical
   Wedge biopsy - Preferred method for dogs <5kg; animals with isolated areas of kidney that need to be avoided; or animals undergo- ing laparotomy for another reason.
 When a specimen is to be used for evaluation of glomerular disease, only cortical tissue should be obtained; biopsy of the medulla is not needed and is associated with a greater risk of hemorrhage, infarction, and fibrosis. The use of general anesthesia is associated with an ability to obtain better-quality specimens and reduces the risk of severe hemorrhage. An adequate sample of cortex has a minimum of five glomeruli when examined by light microscopy, although one glomerulus may be all that is needed to make a definitive diagnosis in animals in which the disease is diffuse (i.e., one in which most glomeruli are involved) and easily recognizable (i.e., amyloidosis).
If a percutaneous method is used to obtain a renal biopsy specimen from a patient with glomerular disease, at least two quality samples of renal cortex (i.e., each >10 mm long) should be obtained, using either a 16-
or 18-gauge needle. A dissecting microscope can be used to verify that adequate biopsy samples have been obtained. One sample should be placed in formalin,
and the other should be divided into two smaller pieces containing glomeruli. One piece is put into a fixative suitable for transmission electron microscopy (TEM) (e.g., 4% formalin plus 1% glutaraldehyde in sodium phosphate buffer), and the other piece is frozen for immunofluorescent microscopy (IFM). An alternative to freezing is to immerse the tissue in ammonium sulfate-N- ethylmaleimide (i.e., Michel’s solution), which preserves tissue-fixed immunoglobulins. Wedge biopsies should
be divided in a similar fashion; tissue for TEM should be minced appropriately. Tissue for TEM should be put into the fixative within 5 minutes of biopsy.
References
1. IRIS Canine GN Study Group Diagnosis Subgroup et al: Consensus recommendations for the diagnostic investigation of dogs with suspected glomerular disease. J Vet Intern Med 27:S19-S26, 2013.
2. Vaden SL et al: Renal biopsy. In Elliot J and Grauer G (eds) Manual of Canine and Feline Nephrology and Urology. Fourth ed. British Small Animal Veterinary Association. In press.
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