Determination of extrarenal plasma clearance and hepatic uptake of technetium- 99m-mercaptoacetyltriglycine in cats

William Tod Drost Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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Mary A. McLoughlin Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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John S. Mattoon Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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Phillip Lerche Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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Valerie F. Samii Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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Stephen P. DiBartola Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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Dennis J. Chew Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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Paul Y. Barthez Département Animaux de Companie, École Nationale Vétérinaire de Lyon, 1 Avenue Bourgelat - BP 83 F-69280 Marcy L'Etoile, France.

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Abstract

Objective—To determine maximum extrarenal plasma clearance of technetium-99m-mercaptoacetyltriglycine (99mTc–MAG3) and maximum extrarenal hepatic uptake of 99mTc–MAG3 in cats.

Animals—6 clinically normal adult cats.

Procedure—Simultaneously, baseline plasma clearance and camera-based uptake of 99mTc–MAG3 were determined in anesthetized cats. Double exponential curves were fitted to plasma clearance data. Injected dose was divided by area under the curve and body weight to determine 99mTc–MAG3 clearance. Regions of interest were drawn around kidneys and liver, and percentage dose uptake was determined 1 to 3 minutes after injection. After bilateral nephrectomy, simultaneous extrarenal plasma clearance and camera- based hepatic uptake of 99mTc–MAG3 were evaluated in each cat.

Results—Mean ± SD baseline plasma clearance and extrarenal clearance were 5.29 ± 0.77 and 0.84 ± 0.47 mL/min/kg, respectively. Mean extrarenal clearance (as a percentage of baseline plasma clearance) was 16.06 ± 7.64%. For right, left, and both kidneys, mean percentage dose uptake was 9.42 ± 2.58, 9.37 ± 0.86, and 18.79 ± 2.47%, respectively. Mean hepatic percentage dose uptake before and after nephrectomy was 12.95 ± 0.93 and 21.47 ± 2.00%, respectively. Mean percentage change of hepatic uptake after nephrectomy was 166.89 ± 23.19%.

Conclusions and Clinical Relevance—In cats, extrarenal clearance of 99mTc–MAG3 is higher than that of other species; therefore, 99mTc–MAG3 is not useful for estimation of renal function in felids. Evaluation of renal function in cats may be more accurate via camera- based versus plasma clearance-based methods because camera-based studies can discriminate specific organs. (Am J Vet Res 2003;64:1076–1080)

Abstract

Objective—To determine maximum extrarenal plasma clearance of technetium-99m-mercaptoacetyltriglycine (99mTc–MAG3) and maximum extrarenal hepatic uptake of 99mTc–MAG3 in cats.

Animals—6 clinically normal adult cats.

Procedure—Simultaneously, baseline plasma clearance and camera-based uptake of 99mTc–MAG3 were determined in anesthetized cats. Double exponential curves were fitted to plasma clearance data. Injected dose was divided by area under the curve and body weight to determine 99mTc–MAG3 clearance. Regions of interest were drawn around kidneys and liver, and percentage dose uptake was determined 1 to 3 minutes after injection. After bilateral nephrectomy, simultaneous extrarenal plasma clearance and camera- based hepatic uptake of 99mTc–MAG3 were evaluated in each cat.

Results—Mean ± SD baseline plasma clearance and extrarenal clearance were 5.29 ± 0.77 and 0.84 ± 0.47 mL/min/kg, respectively. Mean extrarenal clearance (as a percentage of baseline plasma clearance) was 16.06 ± 7.64%. For right, left, and both kidneys, mean percentage dose uptake was 9.42 ± 2.58, 9.37 ± 0.86, and 18.79 ± 2.47%, respectively. Mean hepatic percentage dose uptake before and after nephrectomy was 12.95 ± 0.93 and 21.47 ± 2.00%, respectively. Mean percentage change of hepatic uptake after nephrectomy was 166.89 ± 23.19%.

Conclusions and Clinical Relevance—In cats, extrarenal clearance of 99mTc–MAG3 is higher than that of other species; therefore, 99mTc–MAG3 is not useful for estimation of renal function in felids. Evaluation of renal function in cats may be more accurate via camera- based versus plasma clearance-based methods because camera-based studies can discriminate specific organs. (Am J Vet Res 2003;64:1076–1080)

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