Endogenous creatinine clearance measurement of glomerular filtration rate in dogs

Delmar R. Finco From the Department of Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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Hideki Tabaru From the Department of Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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Scott A. Brown From the Department of Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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Jeanne A. Barsanti From the Department of Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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 DVM, MS

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Summary

Renal clearance procedures were performed on adult mixed-breed dogs with a wide range of renal function. Endogenous creatinine clearance was computed after analyzing plasma and urine for creatinine by use of 2 methods, PAP and kinetic Jaffe. For 20-minute clearance procedures, [14C]inulin clearance was measured simultaneously with endogenous creatinine clearance.

For 111 twenty-minute clearance procedures performed on 24 dogs, [14C]inulin clearance was highly correlated with creatinine clearance for both methods of creatinine analysis (R2 = 0.979 for [14C]inulin-PAP; R2 = 0.943 for [14C]inulin-Jaffe). The absolute values for PAP and [14C]inulin clearance were nearly the same (PAP-to-[14C]inulin clearance ratio = 1.03 ± 0.08), but those for Jaffe clearance were substantially less than those for [14C]inulin clearance (Jaffe-to-[14C]inulin clearance ratio = 0.88 ± 0.10).

The Jaffe-to-[14C]inulin clearance ratio was inversely correlated with degree of renal function (R2= 0.464), whereas the PAP-to-[14C]inulin clearance ratio was not correlated with degree of renal function (R2 = 0.060). Thus, Jaffe-determined creatinine clearance varied, in relation to [14C]inulin clearance, depending on degree of renal function.

In 4 clinically normal dogs, 20-minute and 24-hour sample collections analyzed by use of the PAP method gave clearance values significantly greater, for both periods, than did Jaffe analyses. The PAP-determined creatinine clearance values were less than, but not significantly different from 20-minute exogenous creatinine clearance values determined 10 days after 24-hour collections.

For 20-minute and 24-hour collections, the difference in clearance values between the PAP and Jaffe methods was attributable mostly to lower plasma creatinine values for the PAP method (mean ± SEM, plasma PAP-to-Jaffe ratio = 0.798 ± 0.053). However, urine creatinine values also were less by use of the PAP method (urine PAP-to-Jaffe ratio = 0.943 ± 0.103).

We conclude that PAP-determined creatinine clearance reliably measured glomerular filtration rate during 20-minute collections, and probably during 24-hour collections as well. By contrast, Jaffe-determined creatinine clearance underestimated glomerular filtration rate by a variable amount.

Summary

Renal clearance procedures were performed on adult mixed-breed dogs with a wide range of renal function. Endogenous creatinine clearance was computed after analyzing plasma and urine for creatinine by use of 2 methods, PAP and kinetic Jaffe. For 20-minute clearance procedures, [14C]inulin clearance was measured simultaneously with endogenous creatinine clearance.

For 111 twenty-minute clearance procedures performed on 24 dogs, [14C]inulin clearance was highly correlated with creatinine clearance for both methods of creatinine analysis (R2 = 0.979 for [14C]inulin-PAP; R2 = 0.943 for [14C]inulin-Jaffe). The absolute values for PAP and [14C]inulin clearance were nearly the same (PAP-to-[14C]inulin clearance ratio = 1.03 ± 0.08), but those for Jaffe clearance were substantially less than those for [14C]inulin clearance (Jaffe-to-[14C]inulin clearance ratio = 0.88 ± 0.10).

The Jaffe-to-[14C]inulin clearance ratio was inversely correlated with degree of renal function (R2= 0.464), whereas the PAP-to-[14C]inulin clearance ratio was not correlated with degree of renal function (R2 = 0.060). Thus, Jaffe-determined creatinine clearance varied, in relation to [14C]inulin clearance, depending on degree of renal function.

In 4 clinically normal dogs, 20-minute and 24-hour sample collections analyzed by use of the PAP method gave clearance values significantly greater, for both periods, than did Jaffe analyses. The PAP-determined creatinine clearance values were less than, but not significantly different from 20-minute exogenous creatinine clearance values determined 10 days after 24-hour collections.

For 20-minute and 24-hour collections, the difference in clearance values between the PAP and Jaffe methods was attributable mostly to lower plasma creatinine values for the PAP method (mean ± SEM, plasma PAP-to-Jaffe ratio = 0.798 ± 0.053). However, urine creatinine values also were less by use of the PAP method (urine PAP-to-Jaffe ratio = 0.943 ± 0.103).

We conclude that PAP-determined creatinine clearance reliably measured glomerular filtration rate during 20-minute collections, and probably during 24-hour collections as well. By contrast, Jaffe-determined creatinine clearance underestimated glomerular filtration rate by a variable amount.

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