Glomerular filtration rate is an index of renal function that indicates blood plasma volume filtered at the glomeruli expressed per unit of time. Estimated GFR, which is calculated from serum creatinine concentration, is used for the classification of chronic renal disease.1 The CT-GFR method was developed to calculate GFR of each kidney as part of preoperative planning for renal transplantation or nephrectomy. In this method, an iodinated contrast medium is used as a tracer and, similar to inulin, is not metabolized in the body and is not reabsorbed nor excreted at the renal tubules.2–4 Because this method uses CT scan data, renal volume and assessment of vascular anatomy (eg, evaluation for malformation of the renal artery) can be performed for surgical planning in addition to estimation of single-kidney GFR.5 Moreover, the results can be obtained on the same day as the evaluation.
However, because of the lack of a standardized methodology, CT-GFR can overestimate or underestimate the GFR, compared with that assessed by inulin clearance. Some previous studies have included evaluation of the whole kidney (renal cortex and medulla) for CT-GFR estimation,6,7 whereas others have included the renal cortex only.8 However, it has been recommended that CT-GFR analysis should be based on evaluation of the renal cortex alone, because glomerular filtration occurs in the renal cortex.8 Anesthesia is required when performing CT scans of animals, and GFR may also be underestimated as a consequence of reduced blood pressure during anesthesia. To extrapolate CT-GFR data obtained from experimental studies to clinical trials, data on CT-GFR measurements under anesthesia adequate for this purpose are needed. Moreover, iodinated contrast media with different osmolalities may have different contrast effects in kidneys9; however, to the authors’ knowledge, no published studies comparing the effects of such media on estimates of CT-GFR have been published.
The purpose of the study reported here was to investigate the effects of ROI (whole kidney [renal cortex and medulla] vs cortex alone), analysis time, analytic procedures, and iodinated contrast medium type (higher vs lower osmolality) on values of CT-GFR in healthy anesthetized dogs and to compare these values with GFR estimated by inulin clearance as a means to identify potential causes for overestimation or underestimation of GFR by the CT method.
The authors had no external financial support for the study and no conflicts of interest to declare.
Area under the curve
Glomerular filtration rate estimated by CT
Glomerular filtration rate
Region of interest
FUJIFILM Monolith Co Ltd, Tokyo, Japan.
Inulead, Fuji Yakuhin Co Ltd, Saitama, Japan
Atropine sulfate injection 0.5 mg, Mitsubishi Tanabe Pharmaceutical Co Ltd, Osaka, Japan.
Vetorphale, Meiji Seika Pharma Co Ltd, Tokyo, Japan.
Propofol intravenous injection 1%, Fresenius Kabi Japan, Tokyo, Japan.
KVS-2100, Kohken Medical Co Ltd, Tokyo, Japan.
Visipaque 320, Daiichi-Sankyo Co Ltd, Tokyo, Japan.
Omnipaque 300, Daiichi-Sankyo Co Ltd, Tokyo, Japan.
Autoenhance A-800, Nemoto Kyorindo, Tokyo, Japan.
Aquilion CXL, Toshiba, Tochigi, Japan.
VirtualPlace Fujin, AZE, Tokyo, Japan.
Dynamic study, Toshiba, Tochigi, Japan.
Microsoft Excel for Mac 2011, version 14.7.1, Microsoft Corp, Redmond, Wash.
Body perfusion, Toshiba, Tochigi, Japan.
SPSS, version 22.0, SPSS Inc, Chicago, Ill.
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