Radiolabeled marker clearance (i.e. renal scintigraphy) can measure the GFR of each kidney individually, which is important if nephrectomy is being considered.
This test requires referral to a facility with the necessary equipment and quarantine facilities (i.e. most veterinary schools and some larger specialty practices with a veterinary radiologist on staff). The radioisotope technetium
99m diethylenetriamine pentaacetic acid (Tc-99m-DTPA) is administered intravenously, and radioisotope uptake in the kidney
is quantified with a gamma camera over three minutes.6 Patients are quarantined for 24 hours afterward to allow the radioactive marker to be cleared.
Case example: Renal scintigraphy in a senior cat with a renal mass
Lobelia, a 13-year-old spayed female domestic shorthaired cat, was presented for evaluation of polycythemia (PCV 61%) and
was found to have a right renal mass. She was not azotemic. Renal scintigraphy was performed. The global GFR of 2.3 ml/min/kg
was within the reference range, and function was almost equally split between the two kidneys. The GFR of the left kidney
was 1.3 ml/kg/min, which was deemed insufficient to maintain normal homeostasis. Chronic kidney failure seemed a likely outcome
if the right kidney was removed. So a subcutaneous vascular access port was placed to facilitate phlebotomy every one to two
months. Lobelia lived for another three years before she succumbed to an abrupt cerebrovascular event.
Cathy E. Langston, DVM, DACVIM
Animal Medical Center
510 East 62nd St.
New York, NY
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