Scintigraphic measurement of renal perfusion using 99m-Technetium mercaptoacetyltriglycine-3 (99mTc-MAG3) was performed on nine bottlenose dolphins (Tursiops truncatus) in a case-control study. Animals were transported on foam pads in covered trucks to the University of California San Diego Medical Center. Upon arrival, an intramuscular injection of 0.07–0.09 mg/kg midazolam was given in the epaxial muscle craniolateral to the dorsal fin for the purpose of sedation. Fifteen minutes after the injection, the animals were transferred by stretcher to a specially engineered table and positioned over a gamma scintillation camera. A 30mCi 99mTc-MAG3 injection was made into the caudal peduncle periarterial venous rete. Serial images of the kidneys were captured for a total scan time of 30 min. Animals were transported back to the home institution and, if needed, midazolam was reversed with 0.005 mg/kg of flumazenil IV. The flow and parenchymal phases of the renograms were analyzed by a board-certified radiologist to determine relative renal perfusion, comparing left and right kidneys within each animal. Results showed dolphins with ultrasound evidence of >5 renal calculi and at least one dilated urinary collecting duct were significantly more likely to have a greater difference in renal perfusion between left and right kidneys compared to dolphins with <5 calculi and undetectable urinary collecting ducts (p=0.02). Although the total number of renal calculi per animal was not a significant predictor of renal perfusion (p=0.48), a dilated urinary collecting duct was a reliable predictor of reduced relative renal perfusion (p=0.02).
The authors thank Dr. Sam Ridgway, CPT Stephen Cassle, CPT Nathan Daughenbaugh, and the U.S. Army veterinary technicians for their intellectual and medical support of this project. For animal care and logistical support, we thank our animal behavior specialists, particularly Dr. Mark Xitco, Brit Swenberg, Brian Weisman, Mark Patefield, Braden Duryee, Christian Harris, and Dennis Regan. This work was supported on all levels by the SSC San Diego Biosciences Division and was funded by the In-house Laboratory and Independent Research Program and the Office of Naval Research.