The quantification of renal function with enhanced computed tomography

Abstract

The changes with time in renal parenchymal and vascular attenuation following injection of an intravascular contrast medium can be exploited to study renal physiology in several ways. Shortly after injection, both contrast medium clearance and fractional vascular volume per unit volume of kidney can be measured on a regional basis by obtaining sequential CT data from one anatomical level and the application of a graphical analysis to the baseline subtracted CT numbers for tissue and vascular regions of interest: c(t) and b(t), respectively. By plotting the ratio c(t)/b(t) against integral of b(t)dt/b(t), both fractional vascular volume and contrast medium clearance can be estimated graphically. At later time points, a semilogarithmic plot against time of the declining attenuation of vascular or parenchymal regions of interest gives information about overall, as opposed to regional, renal function: the gradient estimates the glomerular filtration rate per unit volume of extracellular fluid. Absolute glomerular filtration rates can also be calculated with blood sampling. Although further experimental evaluation is needed, these techniques have a strong theoretical basis, and experimental work performed so far is encouraging. Possible applications of these techniques are discussed.

A simple method to estimate renal volume from computed tomography

“…On average, the ellipsoid method slightly underestimated 3D volumes, but almost all were accurate within 30%. Given the established relationship between renal volume and function, [4][5][6][7][8][9][10][11][12][13][14][15][16] our findings suggest 3D volume software analysis is not necessary when estimating differential renal function.…”

“…[1][2][3] In addition, renal volume estimated by CT also correlates with renal function [4][5][6][7][8][9][10][11] and permits concurrent evaluation of differential renal function. [12][13][14][15][16] Unfortunately, renal volume estimates using CT are time-consuming or require specialized 3D volumetric software, 12,13,15,17,18 which has rarely been made available for use in comparative studies.…”

Renal Volumetric Analysis: A New Paradigm in Renal Mass Treatment Assessment

“…5,8,[10][11][12] The methodology in obtaining the imaging, slice thickness, timing of contrast, selection of the ROI, and calculation of volume has varied. Earlier articles relied on estimation of the renal volume based on an ellipsoid method that is widely used in the renal ultrasound volume calculations.…”

“…There is accumulating evidence for the use of renal volume as a measure of renal function. [5][6][7][8][9][10][11][12] There are no studies, however, reporting volumetric assessments after renal tumor ablation or partial nephrectomy. Thus, the objective of this study was to assess renal volume before and after treatment of patients with renal masses with either partial nephrectomy or radiofrequency ablation (RFA).…”

Imaging Approaches to the Correlation of Structure and Function in the Kidney

“…A scan from the top of the kidneys to the pubic symphysis can be accomplished in 20 s. With the use of contrast agents one can image not only anatomy but also function. Blomley and Dawson [15]have done some interesting work in developing a method to calculate the glomerular filtration rate (GFR) which is described in more detail later.…”