Effects of Renal Scintigraphy Processing with and without Kidney Depth Measurement

Introduction: At our facility, we utilize technetium-99m mercaptuacetylglycine (MAG3) to obtain images. Using the GE Xeleris Renal Analysis Program, we process nuclear medicine renograms to assess the uptake of the radiotracer over time. The processing protocol provides the technologist an opportunity to quantify the depth of each kidney. Currently, our written protocol titled, "Renograms Using Tc-99m MAG3," does not require a kidney depth unless otherwise instructed by the radiologist. One value that our radiologists evaluate when reading a renogram study is the uptake percent, which correlates to differential kidney function. According to our protocol, the normal uptake percent falls between 45-55%. It is unknown if the inclusion of a measured kidney depth from the posterior, significantly affects the uptake percent. This research investigates whether or not our protocol should require the technologist to enter the kidney depth for each patient.

Methods: Retrospectively, 64 patients’ data who had a MAG3 renogram done in 2023 was gathered. Only the data of patients with two native kidneys were reviewed. Utilizing Picture Archiving and Communication System (PACS), prior CT scans for each patient were pulled, and one of our radiologists measured each kidney's depth, in centimeters, from the posterior. These depths were then entered into each patient’s previously processed study on the GE Xeleris Renal Analysis Program and the uptake percent was recorded for the right and left kidneys. The uptake percent was also recorded for each kidney before kidney depths were entered. The percent difference in uptake percentages between each kidney, with and without kidney depth, was also recorded.

Results: Of the 64 renogram studies that were analyzed, four of them were omitted from the study due to anatomical anomalies. Through statistical analysis, a p-value of 2.00 was calculated for both the right and left kidneys, when comparing the percent difference in uptake percent for each kidney with and without a manually entered depth.

Conclusions: In conclusion, a p-value greater than 0.05 indicates that it is not statistically significant to include or exclude a kidney depth of each kidney measured from the posterior only, while processing a renogram. There is no correlation between uptake percent indicating differential kidney function and the depth of each kidney. To further my research, I would measure kidney depth from both the anterior and the posterior in order to get a summation of the two views. A summation would be a more accurate measurement of kidney depth, allowing a radiologist time to assess any overlying tissue present on a CT scan. Any overlying tissue, that is considered being an anatomical anomaly, could alter the position and depth of a kidney. Measuring kidney depth anteriorly and posteriorly would account for any anatomical variances found. This addition of a summation would be especially important for the four studies that were omitted due to incidental findings of masses on the kidneys, which ultimately created inaccurate uptake percentages. To conclude, if an indication on an exam suggests a mass, malignancy, or is for a presurgical workup, it may be advantageous to consider using a summation for special cases.