A novel rotation method with variable-angle anterior probe for correcting the depth of the kidney to optimize renal dynamic imaging.

PURPOSE: We aimed to investigate the effect and significance of the rotation method with variable-angle anterior probe corrected for the depth of two kidneys on the determination of glomerular filtration rate (GFR) in total and single kidneys by the renal dynamic imaging Gates method. METHODS: Seventy-two patients who underwent dynamic renal imaging by the rotation method and abdominal CT in our hospital were collected in the present study. CT scanning, rotation method, Tonnesen's formula, and Li-Qian's formula were compared in terms of the depth of two kidneys, the depth difference between the two kidneys, and the total renal and single GFR obtained by substituting the renal depth values into Gates' formula. RESULTS: ①The depth of kidneys and GFR: Compared to CT, Tonnesen's formula significantly underestimated the depth of both kidneys and the total and single renal GFR (P < 0.05). No significant differences were found in the depth of both kidneys and the total and single renal GFR between Li-Qian's formula and the rotation method (P > 0.05), with a strong agreement and with the least bias in the values measured by the rotation method. ②Renal depth difference: Compared to CT, Tonnesen's formula and Li-Qian's formula underestimated the difference in depth between the two kidneys (P < 0.05). None of the differences were statistically significant based on the rotation method (P > 0.05). The depth difference was positively correlated with the resulting changes in single renal function (|R(CT)-R(Li-Qian)|) and (|R(Rotation)-R(Li-Qian)|) (r = 0.881, 0.641, P < 0.001). As the depth difference increased, Li-Qian's formula could not visualize changes in single renal function accurately. In contrast, the accuracy of the rotation method in assessing single renal function remains unaffected. CONCLUSION: The rotation method obtains an accurate depth and depth difference between the two kidneys without additional CT radiation, enhancing the accuracy of the Gates method for determining total and single renal GFR. Trial registration Medical Ethics Committee of First Hospital of Shanxi Medical University, 2021BAL0146. Registered 12 January 2021.

Establishment of a formula for the estimation of kidney depth in adults and its effect on glomerular filtration rate assessment.

Background: Gates' analysis method for kidney depth (KD) calculation is the only way to determine the glomerular filtration rate (GFR) of the kidney in clinical practice, which posits that the influence of KD on the GFR is more important than other factors. Computed tomography (CT) measurement of the donor KD can improve the accuracy of GFR measurement by Gates' method but will also increase the radiation exposure of kidney transplantation donors. Thus, it is particularly important to establish an accurate empirical formula for KD measurement that is more consistent with the real KD. Methods: In total, 326 potential renal transplantation donors were enrolled in this study. Among these, 167 donors were assigned to the training set to estimate the regression formula of KD measured by CT. The remaining 159 donors were included in the validation set to verify the regression formula. The KD measured by CT and its corresponding GFR was taken as the reference standard. The performances of formulas were then compared. Results: There was no significant statistical difference between the CT-measured KD and the current fitting, Li Q, and Xue JJ formulas (P>0.05). However, significant differences were observed between the KDs calculated using the Taylor, Ma G, and Uchiyama formulas and the CT-measured reference standard KD (P<0.05). Furthermore, there was no notable difference in the GFRL and GFRR corresponding to the CT-measured KD with that of the fitting, Ma G, and Xue JJ formulas (P>0.05). There were also marked differences in the GFRR corresponding to the Li Q's formula (P<0.05), and in the GFR between other estimation methods and the CT measurement (P<0.05). Conclusions: The fitting formula established in this study can play a more important role if an accurate measurement method of the body thickness at the level of the hilum on the body surface can be found.

Feasibility of gamma camera-based GFR measurement using renal depth evaluated by lateral scan of 99mTc-DTPA renography.

OBJECTIVE: Gamma camera-based measurement of glomerular filtration rate (GFR) with 99mTc-diethylenetriaminepentaacetic acid (DTPA) is an established non-invasive measurement of split renal function; however, it is not as accurate as the plasma sample method. Therefore, study into improving the accuracy of such method is clinically relevant. The aim of this study was to elucidate the feasibility of gamma camera-based GFR measurement using renal depth evaluated by lateral scan of 99mTc-DTPA renography and comparing the results with those of GFR using renal depth measured by CT, and three representative formulas. METHODS: The study population comprised 38 patients (median, 69 years; male 28, female 10; median estimated GFR, 67.4 ml/min) with renourinary disorders. Scintigraphy was performed after intravenous injection of 370 MBq 99mTc-DTPA by dynamic data acquisition for 20 min, followed by a bilateral static scan of the abdomen for 3 min. All patients underwent computed tomography (CT) within 2 months from renography. GFR was calculated by renography using renal depth determined in five ways; lateral scan of 99mTc-DTPA, CT, and three formulas previously created with using weight, height and age. GFRs were compared with estimated GFR (eGFR). The depth of both kidneys measured as described above was compared and evaluated the laterality of the renal depth. RESULTS: The median values of GFR calculated with renal depth determined by 99mTc-DTPA renography, CT, and the three formulas were 87.3, 83.9, 67.8, 68.3, and 71.5 ml/min, respectively. All of them correlated significantly with eGFR (r = 0.734, r = 0.687, r = 0.728, r = 0.726, and r = 0.686, respectively), however, no significant difference was observed among five correlation coefficients. Bland-Altman plot revealed that eGFR had error and fixed bias when compared with GFRs calculated using renal depth determined by renography, CT, and Taylor's formula. The depth of both kidneys measured by 99mTc-DTPA renography was equivalent to that measured by CT, however, those measured by the three formulas were significantly smaller than that measured by 99mTc-DTPA renography. The depth of the right kidney was larger than that of the left kidney using all three formulas in all patients. However, CT detected only 66% of patients to have a deeper right kidney than left kidney. CONCLUSION: Lateral scanning is a feasible procedure to measure renal depth for accurate and reasonable split GFR measurements using 99mTc-DTPA renography.