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  • Author or Editor: Hideki Tabaru x
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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 (R 2 = 0.979 for [14C]inulin-PAP; R 2 = 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 (R 2= 0.464), whereas the PAP-to-[14C]inulin clearance ratio was not correlated with degree of renal function (R 2 = 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.

Free access
in American Journal of Veterinary Research

Summary

Clinically normal dogs were evaluated in states of dehydration, euhydration, and after fluid administration to determine effects of hydration state on renal clearance values. Endogenous creatinine, exogenous creatinine, and [14C]inulin clearances, were determined to measure glomerular filtration rate (gfr); in some experiments p-aminohippurate clearance was determined to measure renal plasma flow.

Dehydration caused significant (P < 0.05) decrease in clearance values, compared with euhydration, and clearance values during euhydration were significantly (P < 0.05) less than values obtained after a single gavage with water (30 ml/kg of body weight).

Sustained administration of 3 fluid regimens was evaluated for effects on clearance values (treatment A = 30 ml of lactated Ringer’s solution/kg/h; treatment B = 30 ml of water/kg by gavage hourly; treatment C = 10 ml of glucose:lactated Ringer’s solution/kg/h). All regimens of fluid therapy caused significant P < 0.05), progressive increases in gfr, but treatment C resulted in the most stable gfr values. Increases in clearance values were associated with positive fluid balance; the rate of fluid administration was greater than the rate of urine formation.

Data from 285 gfr determinations on 85 dogs were evaluated retrospectively. For each determination, three 20-minute urine collections were made beginning 40 minutes after 30 ml of water/kg was given by gavage. Values between collections were significantly (P < 0.05) different, but varied by < 3%.

Comparison of methods for measurement of gfr indicated that endogenous creatinine clearance and [14C]inulin clearance were highly correlated (R 2 = 0.82), but mean clearance values were markedly different (mean ± sem, 28.70 ± 0.01 and 37.07 ± 1.29 ml/min, respectively).

Exogenous creatinine clearance and [14C]inulin clearance were highly correlated (R 2 = 0.95), and mean values were 40.54 ± 0.70 and 41.02 ± 0.70 ml/min respectively.

We conclude that: state of hydration has a marked effect on gfr; rate of fluid administration that exceeds rate of urine production results in progressive increases in gfr; a single water gavage of 30 ml/kg gives stable gfr values for three 20-minute collection periods, may avoid subclinical states of dehydration, and facilitates accurate urine collections; and endogenous creatinine clearance, as conducted in this study, does not accurately measure gfr.

Free access
in American Journal of Veterinary Research