Assessment of glomerular filtration rate with dynamic computed tomography in normal Beagle dogs

Abstract

The objective of our study was to determine individual and global glomerular filtration rates (GFRs) using dynamic renal computed tomography (CT) in Beagle dogs. Twenty-four healthy Beagle dogs were included in the experiment. Anesthesia was induced in all dogs by using propofol and isoflurane prior to CT examination. A single slice of the kidney was sequentially scanned after a bolus intravenous injection of contrast material (iohexol, 1 mL/kg, 300 mgI/mL). Time attenuation curves were created and contrast clearance per unit volume was calculated using a Patlak plot analysis. The CT-GFR was then determined based on the conversion of contrast clearance per unit volume to contrast clearance per body weight. At the renal hilum, CT-GFR values per unit renal volume (mL/min/mL) of the right and left kidneys were 0.69 ± 0.04 and 0.57 ± 0.05, respectively. No significant differences were found between the weight-adjusted CT-GFRs in either kidney at the same renal hilum (p = 0.747). The average global GFR was 4.21 ± 0.25 mL/min/kg and the whole kidney GFR was 33.43 ± 9.20 mL/min. CT-GFR techniques could be a practical way to separately measure GFR in each kidney for clinical and research purposes.

Fig. 1

Dynamic CT images centered in the left renal hilum obtained at maximal aortic enhancement with iohexol. The black circle indicates the aorta, the black line indicates the left kidney, and the dotted line indicates the right kidney. Regions of interest (ROI) are drawn around the aorta as well as left and right kidneys. Vessels and fatty tissue are excluded from the ROIs. LK: left kidney, RK: right kidney, AO: aorta.

Fig. 2

Time attenuation curves (TACs) showing iohexol concentrations in the aortic blood (A) and left kidney (B) of a dog. The threshold (arrow) is the background Hounsfield unit (HU) value of the aortic (A) and renal (B) ROIs. The initial postcontrast aortic and renal peak enhancements and their times are shown (cross mark).

Fig. 3

Patlak plots of the right (A) and left (B) kidneys of a Beagle dog. The slope represents the blood clearance (mL/min/unit volume), and the y-intercept indicates the fractional vascular volume (%). Components c(t) and b(t) are the CT values from which the baseline has been subtracted of the renal ROI and the aorta.