Determination of glomerular filtration rate in dogs using contrast-enhanced computed tomography.
The purpose of this project was to establish a procedure and reference values for glomerular filtration rate (GFR) using contrast-enhanced computed tomography (CT) in eight healthy dogs. A single section of the kidney was scanned sequentially after bolus injection (3 ml/s) of iohexol (300 mg/kg). Time-attenuation curves were constructed and the GFR per volume of kidney was calculated using Patlak graphical analysis software. The GFR was then converted from contrast clearance per unit volume (ml/min/ml) to contrast clearance per body weight (ml/min/kg). Individual kidney and global GFR were calculated using both CT and nuclear scintigraphy. Global GFR for each dog was also determined by plasma iohexol clearance. Contrast-enhanced CT underestimated the global GFR compared with the other two methods. The average global GFR was 2.57 +/- 0.33 ml/ min/kg using functional CT and 4.06 +/- 0.37 ml/min/kg using plasma iohexol clearance. There was significant (P < 0.05) interobserver variability of CT GFR of the right kidney and total GFR. There was decreased interobserver variability for the left kidney. There was no difference in the intraobserver variability for CT-determined individual kidney and global GFR. There was no difference between the motion corrected and nonmotion corrected values for individual and global CT GFR. Nuclear scintigraphy produced a slightly higher coefficient of variation than contrast-enhanced CT, 2.9% and 1.0%, respectively. It is hypothesized that altered renal blood flow, hematocrit of the small vessels, and nephrotoxicity play a role in the underestimation of GFR by contrast-enhanced CT.
Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign Urbana, IL, USA. odellk@uiuc.edu
Kristen J
KJ
O'Dell-Anderson
Robert
R
Twardock
Jennifer B
JB
Grimm
Kurt A
KA
Grimm
Peter D
PD
Constable
D000818:Animals; D003287:Contrast Media; D004285:Dogs; D005919:Glomerular Filtration Rate / Q000662:veterinary*; D007472:Iohexol; D007668:Kidney / Q000000981:diagnostic imaging*; D008297:Male; D015588:Observer Variation; D011237:Predictive Value of Tests; D011866:Radioisotope Renography / Q000662:veterinary; D012016:Reference Values; D014057:Tomography, X-Ray Computed / Q000662:veterinary*
D003287:Contrast Media; D007472:Iohexol