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Renal 131I-hippurate clearance overestimates true renal blood flow in the instrumented conscious dog.

Authors :
Visscher CA
De Zeeuw D
Navis G
Van Zanten AK
De Jong PE
Huisman RM
Source :
The American journal of physiology [Am J Physiol] 1996 Aug; Vol. 271 (2 Pt 2), pp. F269-74.
Publication Year :
1996

Abstract

We evaluated renal 131I-hippurate clearance (ERPFhip) as a measure of renal blood flow (RBF) in chronically instrumented conscious dogs. When adjusted for renal hippurate extraction (Ehip, 0.77 +/- 0.01) and hematocrit (Hct, 39.7 +/- 1%), calculated RBFhip (656 +/- 37 ml/min) markedly exceeded renal blood flow measured with renal artery blood flow probes (RBFprobe, 433 +/- 27 ml/min). The discrepancy could not be explained by flow probe calibration, because in vivo comparison of flow probe values with renal venous outflow showed only a slight underestimation of renal blood flow (slope 0.93, 95% confidence interval 0.89-0.97). Redistribution of hippurate from erythrocytes into renal venous plasma during or shortly after blood sampling led to an underestimation of Ehip by 4 +/- 1% and thus could only explain a small part of the difference. Extrarenal hippurate clearance was excluded, because the amount of 131I-hippurate cleared from plasma equaled that appearing in the urine (303 +/- 17 and 307 +/- 17 ml/min). Applying these corrections, we found that RBFhip still exceeded RBFprobe by 37 +/- 3%. These data indicate that renal blood flow measured by the hippurate clearance technique markedly overestimates true renal blood flow. Because other errors were excluded, a combination of sampling of nonrenal blood and intrarenal hippurate extraction from erythrocytes might play a role.

Details

Language :
English
ISSN :
0002-9513
Volume :
271
Issue :
2 Pt 2
Database :
MEDLINE
Journal :
The American journal of physiology
Publication Type :
Academic Journal
Accession number :
8770157
Full Text :
https://doi.org/10.1152/ajprenal.1996.271.2.F269