Abstract
This study evaluates the usefulness of parameters allowing assessment of renal function in absolute values in dynamic renal scintigraphy (DRS) with 99mTc-ethylenedicysteine (99mTc-EC) uptake constant (K), mean transit time (MTT), and parenchymal transit time (PTT) in the diagnosis of obstructive uro/nephropathy. The study included 226 people: 20 healthy volunteers, for whom normative values of assessed parameters were determined, and 206 patients. Reproducibility of results obtained by two independent operators, specificity, correlation with estimated GFR (eGFR), and Cohen’s kappa were used to evaluate reliability of assessed parameters. Normative values were as follows: K ≥ 1.6, MTT ≤ 250 s, and PTT ≤ 225 s. Reproducibility of determination of K (rs = 0.99) and MTT (rs = 0.98) was significantly higher than that of PTT (rs = 0.95) (p = 0.001). Specificity was 100% for K, 81% for MTT, and 91% for PTT. Correlation of eGFR with K (rs = 0.89) was significantly higher than with PTT (rs = 0.53) and with split function (SF) (rs = 0.66) (p < 0.0001). Cohen’s kappa was κ = 0.89 for K, κ = 0.88 for MTT, and κ = 0.77 for PTT. In a group of patients where standard DRS parameters are unreliable (bilateral obstructive uro/nephropathy or single functioning kidney), the use of K (the most effective among assessed parameters) changed the classification of 23/79 kidneys (29%). K enables reproducible assessment of absolute, individual kidney function without modifying routine DRS protocol. Diagnostic value of MTT and PTT is limited.
Highlights
One of the primary indications for dynamic renal scintigraphy (DRS) is the diagnosis of obstructive uro/nephropathy
In order to assess reproducibility of K, mean transit time (MTT), and parenchymal transit time (PTT), susceptibility of the method of their determination to errors resulting from the subjective factor was analyzed
The results of the research carried out in this study clearly indicate that the original uptake constant K is a better and more practical parameter for the assessment of renal function in DRS
Summary
One of the primary indications for dynamic renal scintigraphy (DRS) is the diagnosis of obstructive uro/nephropathy. Processing units of modern gamma cameras usually have software allowing determination of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) clearance for the determination of glomerular filtration rate (GFR) or 99mTc-mercaptoacetyltriglycine (99mTcMAG3) clearance for the determination of tubular extraction rate (TER) based on DRS study (camera-based clearance) These procedures were developed by Schlegel et al for 131I-orthoidohippurate (131I-OIH) [2] and by Gates for 99mTc-DTPA [3] and were later adapted for 99mTc-MAG3. These methods are more accessible than the most accurate and precise radioisotope technique for determining GFR based on a multisample clearance of 99mTc-DTPA Their accuracy is being questioned and they require taking into account additional information, such as precise measurement of the activity of radiopharmaceutical administered to the patient or measuring depth of kidneys in order to correct the attenuation of radiation by tissues located between the camera detector and the kidney [4]. Protocol for the calculation of 99mTc-ethylenedicysteine (99mTc-EC) camera-based clearance was not developed yet
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