Renal size should be considered when evaluating the risks of needle biopsy of the kidney. Reduction in the thickness of the
renal cortex as a consequence of chronic progressive renal disease increases the likelihood of needle damage to larger intrarenal
vessels such as the arcuate arteries.
Figure 6: A schematic illustration of a biopsy of the renal cortex using a Tru-Cut biopsy needle. Note that the needle has
not traversed the corticomedullary junction.
Because excessive hemorrhage is a potentially serious complication of this procedure, patients with a hemorrhagic tendency
should not be undergo a biopsy unless abnormalities in hemostasis can first be adequately controlled. Likewise, hypertension
has been associated with an increased incidence of hemorrhage and arteriovenous fistulas in humans after renal biopsy. Therefore,
hypertension should be controlled before needle biopsy of the kidney.
How should renal biopsy samples be handled?
If a decision to perform a renal biopsy is deemed to be in the patient's best interest, before performing the procedure, contact
a laboratory familiar with evaluation of kidney biopsy samples, and ask for specific directions on how to process the sample.
For example, request information about how to process samples for standard light, immunofluorescent and electron microscopy,
as well as immunohistochemical techniques.
Figure 7: A photograph illustrating a linear infarct in the renal cortex of a dog's right kidney. A needle biopsy sample taken
from this region one week previously contained only tissue from the renal cortex.
Now what's your opinion?
Key point: Since renal biopsy procedures are associated with significant risks, they should not be performed unless the associated
benefits are likely to outweigh those risks for the patient's welfare. After considering this information, how would you respond
to the question: Are the probable benefits associated with needle biopsy of this cat's kidney likely to outweigh the risks
associated with this procedure?
Figure 8: A photograph illustrating a large, healed infarct in the caudal pole of the right kidney of an adult female miniature
schnauzer. A Tru-Cut biopsy needle was used to obtain a sample containing cortex and medulla from this region six months previously.
In formulating your answer, consider the following:
1. What diagnostic, prognostic or therapeutic goals are likely to be achieved by evaluation of kidney biopsy samples?
2. Will the benefits associated with the technique of ultrasound-guided kidney biopsy be sufficient to justify the associated
risks and costs?
Dr. Osborne, a diplomate of the American College of Veterinary Internal Medicine, is professor of medicine in the Department of Small
Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota.