Page 701 - Small Animal Internal Medicine, 6th Edition

CHAPTER 39 Diagnostic Tests for the Urinary System 673

and establishing the response of the patient to therapy or the needle be directed along the long axis of the kidney, solely
progression of previously documented renal disease. Pro- through cortical tissue. Because of the small size of the feline
VetBooks.ir teinuria is a common indication for renal biopsy in dogs and kidney, it is common to obtain relatively large amounts of
medullary tissue, which has been associated with infarction
cats (Video 39.1).
Several techniques for renal biopsy are available; these
After biopsy using the open approach or keyhole tech-
include blind percutaneous, laparoscopic, keyhole, open, and fibrosis.
and ultrasonography-guided approaches. The choice of tech- nique, the kidney should be digitally compressed for 5
nique is dependent largely on the experience and technical minutes and, after release, the abdomen inspected for hem-
skill of the operator, species to be biopsied, and size of sample orrhage. The biopsy sample may be dislodged from the
required. The blind percutaneous technique works well in biopsy instrument using a stream of sterile saline from a
cats because their kidneys can be readily palpated and syringe or, alternatively, the biopsy instrument may be
immobilized. Laparoscopy allows direct visualization of the immersed directly in fixative. For routine histopathology, the
kidney and detection of hemorrhage but requires special sample should be fixed in buffered 10% formalin for at least
equipment and expertise. The keyhole approach occasionally 3 to 4 hours. For immunofluorescence studies, the sample
is used in dogs but is useful only if the operator is experi- can be preserved in Michel’s transport medium. Immunopa-
enced with the technique. Modifications of the keyhole tech- thology studies also may be performed by a peroxidase-
nique and use of laparoscopy do not necessarily improve the antiperoxidase method using formalin-fixed samples without
quality of the biopsy specimen obtained or decrease the com- the need for special preservation of the sample.
plication rate. If the operator is relatively inexperienced with After renal biopsy, a brisk fluid diuresis should be initi-
renal biopsy or a larger sample is required, wedge biopsy via ated to prevent potential clot formation in the renal pelvis.
laparotomy is recommended. Advantages of this procedure The patient’s hematocrit and plasma protein concentration
include the ability to inspect the kidneys and other abdomi- should be monitored at appropriate intervals over the next
nal organs visually, choose the specific biopsy site, take an 12 to 24 hours to detect serious hemorrhage.
adequately sized sample, and observe the kidney for hemor- The most common complication of renal biopsy is hem-
rhage. Ultrasonography-guided techniques can be per- orrhage. Subcapsular hemorrhage may occur at the site of
formed under sedation, allow specific regions of the kidney biopsy, and some patients experience microscopic hematuria
to be selected for biopsy, and allow for the evaluation of during the first 48 hours after biopsy. Macroscopic hematu-
hemorrhage postbiopsy. Some techniques require general ria is less common. In one study, severe hemorrhage occurred
anesthesia to provide adequate patient restraint and analge- after renal biopsy in 10% of dogs and 17% of cats, but gross
sia, but needle biopsies of the kidney can be obtained from hematuria was uncommon (4% of dogs and 3% of cats).
dogs and cats under ultrasound guidance using sedation. Severe hemorrhage into the peritoneal cavity should be
Occasionally, tissue architecture is less important (e.g., renal treated aggressively by compression bandage of the abdomen,
lymphosarcoma, feline infectious peritonitis), and aspiration fresh whole blood transfusion, and exploratory surgery if
of the kidney using a 23- or 25-gauge needle may provide necessary. Rarely, hydronephrosis may complicate renal
useful material for cytology. biopsy. If the renal pelvis is penetrated by the biopsy needle,
Before renal biopsy, an IV catheter should be placed and bleeding may occur and clot formation can lead to obstruc-
clotting ability evaluated (see Chapter 87). The patient’s tion of the kidney and hydronephrosis. This complication
hematocrit and plasma protein concentration should be should be considered if progressive renal enlargement is
determined before biopsy but after adequate rehydration detected after renal biopsy. The risk of this complication is
with parenteral fluids. Hematocrit and plasma protein con- minimized by limiting the biopsy site to the renal cortex and
centration then may be monitored after biopsy to detect instituting a fluid diuresis afterward.
hemorrhage.
The most commonly used biopsy instruments consist of Suggested Readings
modifications of the Franklin-modified Vim Silverman Bland SK, et al. Characterization of kidney injury molecule-1 in
needle and Tru-Cut biopsy needle. Spring-loaded biopsy cats. J Vet Int Med. 2014;28:1454.
units (e.g., Bard Biopty-Cut, Bard Biopsy Systems, Tempe, DeLoor J, et al. Urinary biomarkers for acute kidney injury in dogs.
AZ) allow for the rapid and efficient retrieval of cores of renal J Vet Int Med. 2013;27:998.
tissue for histopathologic evaluation. Excessive penetration Geddes RF, et al. Relationship between plasma fibroblast growth
of the kidney with the outer cannula of the Franklin-modified factor-23 concentration and survival time in cats with chronic
Vim Silverman instrument should be avoided to prevent kidney disease. J Vet Int Med. 2015;29:1494.
retrieval of an insufficient amount of renal cortex. Most Ghys LFE, et al. Evaluation of cystatin C for the detection of chronic
kidney disease in cats. J Vet Int Med. 2016;30:1074.
biopsy needles have an outer cannula that advances 23 to Hall JA, et al. Comparison of serum concentrations of symmetric
25 mm, and caution should be taken when directing the dimethylarginine and creatinine as kidney function biomarkers
angle of the biopsy instrument to avoid the renal hilus and in cats with chronic kidney disease. J Vet Int Med. 1676;28:2014.
major vessels. Samples containing large amounts of medulla Hall JA, et al. Comparison of serum concentrations of symmetric
are more likely to contain large vessels and lead to infarction dimethylarginine and creatinine as kidney function biomarkers
of renal tissue. Therefore it is recommended that the biopsy in healthy geriatric cats fed reduced protein food enriched with