Measurement of single kidney glomerular filtration rate in dogs using dynamic contrast-enhanced magnetic resonance imaging and the Rutland-Patlak plot technique

Abstract

BackgroundNephropathies are among the most common diseases in dogs. Regular examination of the kidney function plays an important role for an adequate treatment scheme. The determination of the glomerular filtration rate (GFR) is seen as the gold standard in assessing the kidney status. Most of the tests have the disadvantage that only the complete glomerular filtration rate of both kidneys can be assessed and not the single kidney glomerular filtration rate. Imaging examination techniques like dynamic contrast-enhanced magnetic resonance imaging have the potential to evaluate the single kidney GFR. There are studies in human medicine describing the determination of the single kidney GFR using this technique. To our knowledge there are no such studies for dogs.ResultsAn exponential fit was found to describe the functional interrelation between signal intensity and contrast medium concentrations. The changes of contrast medium concentrations during the contrast medium bolus propagation were calculated. The extreme values of contrast medium concentrations in the kidneys were reached at nearly the same time in every individual dog (1st maximum aorta 8.5 s, 1st maximum in both kidneys after about 14.5 s; maximum concentration values varied between 17 and 125 µmol/mL in the aorta and between 4 and 15 µmol/mL in the kidneys). The glomerular filtration rate was calculated from the concentration changes of the contrast medium using a modified Rutland-Patlak plot technique. The GFR was 12.7 ± 2.9 mL/min m2 BS for the left kidney and 12.0 ± 2.2 mL/min/m2 BS for the right kidney. The mean values of the coefficient of determination of the regression lines were averagely 0.91 ± 0.08.ConclusionsThe propagation of contrast medium bolus could be depicted well. The contrast medium proceeded in a similar manner for every individual dog. Additionally, the evaluation of the single kidney function of the individual dogs is possible with this method. A standardized examination procedure would be recommended in order to minimize influencing parameters.Electronic supplementary materialThe online version of this article (10.1186/s13028-018-0423-3) contains supplementary material, which is available to authorized users.

Assessment of glomerular filtration rate measurement in dogs using dynamic contrast CT compared to serum iohexol clearance

“…This report agrees with a previous study for GFR estimation by scintigraphy that suggested using 30‐120 s intervals 32 . A study for GFR estimation by MRI suggested the evaluation interval for the Rutland‐Patlak plot technique was 60 sec after the second maximum of contrast media in the aorta (32.2 s) 37 . In our study, the second maximum of the contrast media in the aorta occurred on average after 25.64 ± 5.78 s. Therefore, in this study using an evaluation interval of 30 to 120 sc should be suitable, and this is the equilibrium time perod in healthy dogs.…”

“…32 A study for GFR estimation by MRI suggested the evaluation interval for the Rutland-Patlak plot technique was 60 sec after the second maximum of contrast media in the aorta (32.2 s). 37 In our study, the second maximum of the contrast media in the aorta occurred on average after 25.64 ± 5.78 s. Therefore, in this study using an evaluation interval of 30 to 120 sc should be suitable, and this is the equilibrium time perod in healthy dogs. Unfortunately, the longer time interval of more than 120 sc cannot be tested in our study because the data were only recorded for two min.…”

“…In this period, the slope of the Patlak plot will be equal to the GFR. The time interval should be started after the second maximum of the contrast media concentration in the aorta, 37 and must be ended before the contrast media leaves the renal pelvis and enters the ureter. The longer time limit (at ≥80sec after the contrast media appearance) leads to a greater underestimation of CT‐GFR compared to GFR determined by inulin clearance 18 .…”

Methods for Assessment of the Glomerular Filtration Rate in Laboratory Animals

“…Regarding the specifications of MRI-GFR measurement, some researchers have proposed the demand for standardized procedures, such as the anesthesia protocol, automatic contrast injection, regions of interest location and size, and time interval for RPP integration. Moreover, a cyst/fibrosis segmentation algorithm should be developed to not only separate a cyst from healthy kidney tissue but to also calculate the three-dimensional volume of the kidney to improve the accuracy and reduce the influence of several factors [ 70 , 71 ].…”