Evaluation of a single injection method, using iohexol, for estimating glomerular filtration rate in cats and dogs

Scott A. Brown From the Department of Physiology and Pharmacology (Brown, Finco, Tarver, Cooper), College of Veterinary Medicine, and Department of Pharmaceutics (Boudinot, Wright), College of Pharmacy, University of Georgia, Athens, GA 30602.

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Delmar R. Finco From the Department of Physiology and Pharmacology (Brown, Finco, Tarver, Cooper), College of Veterinary Medicine, and Department of Pharmaceutics (Boudinot, Wright), College of Pharmacy, University of Georgia, Athens, GA 30602.

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F. Douglas Boudinot From the Department of Physiology and Pharmacology (Brown, Finco, Tarver, Cooper), College of Veterinary Medicine, and Department of Pharmaceutics (Boudinot, Wright), College of Pharmacy, University of Georgia, Athens, GA 30602.

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Jennifer Wright From the Department of Physiology and Pharmacology (Brown, Finco, Tarver, Cooper), College of Veterinary Medicine, and Department of Pharmaceutics (Boudinot, Wright), College of Pharmacy, University of Georgia, Athens, GA 30602.

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Stacy L. Tarver From the Department of Physiology and Pharmacology (Brown, Finco, Tarver, Cooper), College of Veterinary Medicine, and Department of Pharmaceutics (Boudinot, Wright), College of Pharmacy, University of Georgia, Athens, GA 30602.

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Tanya Cooper From the Department of Physiology and Pharmacology (Brown, Finco, Tarver, Cooper), College of Veterinary Medicine, and Department of Pharmaceutics (Boudinot, Wright), College of Pharmacy, University of Georgia, Athens, GA 30602.

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Abstract

Objective

To evaluate the utility of a method for estimating glomerular filtration rate (GFR) after single IV administration of iohexol.

Design

The plasma clearance of iodine (PCI), taken as the quotient of the administered dose of iodine (300 to 600 mg of l/kg of body weight) divided by the area under the plasma iodine concentration versus time curve determined by 4 methods (PCI1–PCI4). The results for PCI were compared with simultaneously obtained values for the urinary clearance of exogenously administered creatinine (CCr), a widely accepted method for the measurement of GFR in cats and dogs.

Animals

Cats and dogs that were renal intact (n = 5 cats; n = 1 dog) or had renal mass reduced by partial nephrectomy (n = 5 cats; n = 7 dogs).

Results

Values for PCI were closely related (R2 values ranged from 0.947 to 0.992; P < 0.0001 in all cases) to CCr. Despite this close correlation between CCr and PCI, the 95% confidence interval for the difference between PCI3 and CCr included values that exceeded 1.4 ml/min/kg, which represents 50% of the mean value for CCr in renal-intact cats.

Conclusions

Determination of PCI provided a reliable estimate of GFR in cats and dogs of this study. However, differences between 1 of the methods (PCI3) and CCr are clinically important, emphasizing the need to use more than simple linear regression analysis and correlation coefficients when attempting to validate new measurement techniques.

Clinical Relevance

The determination of PCI provided a reliable estimate of GFR in cats and dogs of this study. (Am J Vet Res 1996;57:105-110)

Abstract

Objective

To evaluate the utility of a method for estimating glomerular filtration rate (GFR) after single IV administration of iohexol.

Design

The plasma clearance of iodine (PCI), taken as the quotient of the administered dose of iodine (300 to 600 mg of l/kg of body weight) divided by the area under the plasma iodine concentration versus time curve determined by 4 methods (PCI1–PCI4). The results for PCI were compared with simultaneously obtained values for the urinary clearance of exogenously administered creatinine (CCr), a widely accepted method for the measurement of GFR in cats and dogs.

Animals

Cats and dogs that were renal intact (n = 5 cats; n = 1 dog) or had renal mass reduced by partial nephrectomy (n = 5 cats; n = 7 dogs).

Results

Values for PCI were closely related (R2 values ranged from 0.947 to 0.992; P < 0.0001 in all cases) to CCr. Despite this close correlation between CCr and PCI, the 95% confidence interval for the difference between PCI3 and CCr included values that exceeded 1.4 ml/min/kg, which represents 50% of the mean value for CCr in renal-intact cats.

Conclusions

Determination of PCI provided a reliable estimate of GFR in cats and dogs of this study. However, differences between 1 of the methods (PCI3) and CCr are clinically important, emphasizing the need to use more than simple linear regression analysis and correlation coefficients when attempting to validate new measurement techniques.

Clinical Relevance

The determination of PCI provided a reliable estimate of GFR in cats and dogs of this study. (Am J Vet Res 1996;57:105-110)

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