Noninvasive measurement of concurrent single-kidney perfusion, glomerular filtration, and tubular function

Abstract

To assess the reliability of electron beam computed tomography (EBCT), measurements of single-kidney renal blood flow (RBF), glomerular filtration rate (GFR), and intratubular contrast medium concentration (ITC) of radiographic contrast media were quantified in anesthetized pigs before and after acetylcholine-induced vasodilation and diuresis. EBCT measurements were compared with those obtained with intravascular Doppler and inulin clearance. The capability of EBCT to detect chronic changes in single-kidney function was evaluated in pigs with unilateral renal artery stenosis, and their long-term reproducibility in normal pigs was studied repeatedly at 1-mo intervals. EBCT-RBF (ml/min) correlated with Doppler-RBF as RBF(EBCT) = 45 + 1.07 * RBF(Doppler), r = 0.81. EBCT-GFR (ml/min) correlated with inulin clearance as GFR(EBCT) = 11.7 + 1.02 * GFR(inulin), r = 0.80. During vasodilation, RBF and GFR increased, whereas ITC decreased along the nephron. In renal artery stenosis, single-kidney GFR decreased linearly with the degree of stenosis, and ITC increased along the nephron, indicating increased fluid reabsorption. EBCT-RBF, GFR, and ITC were similar among repeated measurements. This approach might be invaluable for simultaneous quantification of regional hemodynamics and function in the intact kidneys, in a manner potentially applicable to humans.

TGF Expression and Macrophage Accumulation in Atherosclerotic Renal Artery Stenosis

“…On the third day of the protocol, the right internal jugular vein was cannulated with a 6F sheath and blood samples were drawn from the right and left renal veins and infrarenal inferior vena cava with a 5F pigtail Cobra catheter (Cook Inc, Bloomington, IN) for venous oxygen and plasma renin activity. The catheter was then exchanged for 5F pigtail, which was placed into the superior vena cava for central venous injection of contrast for transit time studies using a multidetector computed tomography (MDCT) (15). Additional images were reconstructed at 0.6-mm slice thickness for quantitative vascular stenosis evaluation (16).…”

“…Image analysis was performed using ANALYZE (Biomedical Imaging Resource Center, Mayo Clinic, Rochester, MN). Analysis of MDCT flow studies were undertaken by selecting a ROI in cross-sectional images from the aorta, individual kidney cortex, and medulla (15). Single-kidney blood flows were determined as the sum of medullary and cortical blood flows, defined by medullary and cortical perfusion per cubic centimeter of renal tissue and volumes calculated using the stereology module within ANALYZE.…”

Renal Perfusion and Hemodynamics: Accurate in Vivo Determination at CT with a 10-Fold Decrease in Radiation Dose and HYPR Noise Reduction

“…Each CT study was performed to assess cortical and medullary perfusion, renal blood flow (RBF), and glomerular filtration rate (GFR) (10)(11)(12)(13)(14)(15)(16). One to 2 seconds before scanning, a 0.5-mL bolus of contrast medium (Isovue 370; Bracco Diagnostics, Princeton, NJ) per kilogram of body weight was injected into the right atrium by using a power injector connected to the catheter by a 36-inch contrast medium-filled tube (10)(11)(12)(13)(14)(15)(16). For the routine CT perfusion acquisition, scanning was performed at 80 kV and 160 mAs in the sequential mode, with 24 ϫ 1.2-mm collimation and a 0-mm table feed (17).…”

“…Average tissue attenuation in each image was automatically calculated, and the changes in attenuation over time were plotted as TACs. These TACs were fitted by using extended gamma-variate curve-fitting algorithms and the curve-fitting parameters used to obtain measures of renal function (15). The parameters obtained from the vascular curve in each region of the kidney were used to calculate regional perfusion.…”

“…RBF (in milliliters per minute) was subsequently calculated as the sum of cortical and medullary blood flows, each obtained as the product of the perfusion and volume of the respective region. GFR (in milliliters per minute) was calculated from the right and left cortical TACs by utilizing the slope of the proximal tubular curve, aortic area, and cortical volume (15). Renal volumes were determined by using data from a separate scan during the same study (14).…”