Development and autoregulation of kidney function in children: a retrospective study using 99mTc-MAG3 renography

BACKGROUND

Both the development of kidney function in healthy children and autoregulation ability of kidney function in patients with asymmetric kidneys are important in clinical diagnosis and treatment of kidney-related diseases, but there are however only limited studies. This study aimed to investigate development of kidney function in normal children with healthy symmetric kidneys and autoregulation of the healthy kidney compensating the functional loss of a diseased one in children with asymmetric kidneys.

METHODS

Two hundred thirty-seven children (156 male, 81 female) from 0 to 20y (average 4.6y ± 5.1) undergoing ^99mTc-MAG3 renography were included, comprising 134 with healthy symmetrically functioning kidneys and 103 with asymmetric kidneys. Clearance was calculated from kidney uptakes at 1-2 min. A developmental model between MAG3 clearance (CL) and patient age in normal group was identified (CL = 84.39Age^0.395 ml/min, r = 0.957, p < 0.001). The clearance autoregulation rate in abnormal group with asymmetric kidneys was defined as the ratio of the measured MAG3 clearance and the normal value predicted from the renal developmental model of normal group.

RESULTS

No significant difference of MAG3 clearance (p = 0.723) was found between independent abnormal group and normal group. The autoregulation rate of kidney clearance in abnormal group was 94.2% on average, and no significant differences were found between two age groups (p = 0.49), male and female (p = 0.39), and left kidney and right kidney (p = 0.92) but two different grades of asymmetric kidneys (p = 0.02).

CONCLUSIONS

The healthy kidney of two asymmetric kidneys can automatically regulate total kidney function up to 94% of two symmetric kidneys in normal children.

Assessment of Individual Renal Function Using 99mTc-MAG3 Renography

BACKGROUND/AIM

This study performed ^99mTc-MAG₃ renal scintigraphy on rabbit kidneys and evaluated its ability to identify obstructive or non-obstructive kidneys.

MATERIALS AND METHODS

Renal function was assessed during a four-week post-obstruction period by obtaining planar images of ^99mTc-MAG₃ activity following an ear vein injection. The individual renal function was evaluated by renal scintigraphy in conjunction with histopathological and morphological examinations.

RESULTS

The renal perfusion of ^99mTc-MAG₃ in the right kidney with a ureteral obstruction decreased with time. The width, height, and cortical thickness of the obstructed right kidney were significantly larger than those of the left kidney. A histopathological examination four weeks after the ureteral obstruction revealed a typical pattern of urinary tract obstruction, including multiple tubules, enlargement of the interstitial area, and cytoplasmic vacuoles.

CONCLUSION

^99mTc-MAG₃ renal scintigraphy provides the kidney shape and size and can identify potential obstructive and non-obstructive kidneys in rabbits.

Head to head comparison of [99mTc]Tc(CO)3(NTA) and [99mTc]Tc-MAG3 in patients with suspected obstruction

PURPOSE

^99mTc-tricarbonyl-nitrilotriacetic acid, [^99mTc]Tc(CO)₃(NTA), is a new ^99mTc-renal radiopharmaceutical with a clearance equal to that of ¹³¹I-ortho-iodohippuran, [¹³¹I]I-OIH. Our purpose was to compare the performance of [^99mTc]Tc(CO)₃(NTA) and [^99mTc]Tc-MAG3 in patients with suspected obstruction.

METHODS

[^99mTc]Tc(CO)₃(NTA) was prepared with commercially available NTA ligand and CRS Isolink kit, and isolated by HPLC. Eighteen adult patients referred for diuretic renography received an intravenous injection of approximately 40 mg of furosemide 15 min prior to either [^99mTc]Tc(CO)₃(NTA) or [^99mTc]Tc-MAG3 (mean activity of 47 ± 4.4 MBq). Data were acquired for 24 min followed by an anterior image of the liver and gall bladder and a measure of voided volume. Patients received a second furosemide injection equal to one third of the original dose followed fifteen minutes later by administration of the alternate tracer, mean activity of 320 ± 34 MBq. Clearances were measured using a camera-based technique.

RESULTS

The clearance of NTA was greater than that of MAG3, 331 ± 146 versus 271 ± 105 mL/min/1.73 m², respectively, p < 0.0001. The kidney to background ratio for NTA was greater than that of MAG3 for both left and right kidneys, p < 0.001; the 20 min/maximum count ratio was significantly less, p < 0.0001. There was no significant difference in the voiding volumes following NTA and MAG3 administration, 598 ± 237 mL versus 498 ± 170 mL, respectively, p = 0.07. Gall bladder activity was not observed with NTA but was present in 6/17 MAG3 studies. Images and renogram curves were comparable except for two patients where the NTA study excluded obstruction but the MAG3 study suggested an indeterminate or obstructed kidney.

CONCLUSIONS

Unlike MAG3, NTA is not eliminated via the hepatobiliary track. Moreover, NTA has a higher kidney to background ratio and more rapid clearance than MAG3. These advantages should allow more robust camera-based clearance measurements and may lead to better discrimination between obstructed and non-obstructed kidneys.

U.S. Diagnostic Reference Levels and Achievable Administered Activities for Adult Renal Scintigraphy: An Analysis of the Intersocietal Accreditation Committee Nuclear Laboratories

The goal of this work was to determine U.S. diagnostic reference levels (DRLs) and achievable administered activities (AAAs) for adult renal scintigraphy. Methods: Under an Institutional Review Board-approved protocol, data were collected from the Intersocietal Accreditation Commission during one 3-y accreditation cycle encompassing 110 facilities. Elements included radiopharmaceutical, administered activity, practice type, and examination volume. DRLs and AAAs were calculated and compared with non-U.S. values and societal recommendations as available. Results: Ninety-three facilities provided data on ^99mTc-mercaptoacetyltriglycine (^99mTc-MAG3), and 15 provided data on ^99mTc-diethylenetriaminepentaacetic acid (^99mTc-DTPA) for adult renal scintigraphy exams. Analysis demonstrated a DRL of 392.2 MBq (10.6 mCi) for ^99mTc-MAG3 and 531.7 MBq (14.4 mCi) for ^99mTc-DTPA, with an AAA of 370 MBq (10 mCi) for ^99mTc-MAG3 and 445.9 MBq (12.1 mCi) for ^99mTc-DTPA. Conclusion: The resultant calculated novel U.S. DRLs and AAAs may serve as benchmarks that nuclear medicine facilities may use to refine renal scintigraphy protocols, reduce patient doses, and potentially guide future societal guideline recommendations.

99mTc-MAG3 Diuretic Renography: Intra- and Inter-Observer Repeatability in the Assessment of Renal Function

The aim of the present study is to evaluate the intra- and inter-observer agreement in assessing the renal function by means of ^99mTc-MAG3 diuretic renography. One hundred and twenty adults were enrolled in the study. One experienced and one junior radiographer processed the renograms twice by assigning manual and semi-automated regions of interest. The differential renal function (DRF, %), time to maximum counts for the right and left kidney (T_maxR-T_maxL, min) and time to half-peak counts (T_1/2, min) were calculated. The Bland–Altman analysis (bias±95% limits of agreement), Lin’s concordance correlation coefficient and weighted Fleiss’ kappa coefficient were used to assess agreement. Based on the Bland–Altman analysis, the intra-observer repeatability results for the experienced radiographer using the manual and the semi-automated techniques were 0.2 ± 2.6% and 0.3 ± 6.4% (DRF), respectively, −0.01 ± 0.24 and 0.00 ± 0.34 (T_maxR), respectively, and 0.00 ± 0.26 and 0.00 ± 0.33 (T_maxL), respectively. For the junior radiographer, the respective results were 0.5 ± 5.0% and 0.8 ± 9.4% (DRF), 0.00 ± 0.44 and 0.01 ± 0.28 (T_maxR), and 0.01 ± 0.28 and −0.02 ± 0.44 (T_maxL). The inter-observer repeatability for the manual method was 0.6 ± 5.0% (DRF), −0.10 ± 0.42 (T_maxR) and −0.05 ± 0.38 (T_maxL), and for the semi-automated method −0.2 ± 9.1% (DRF), 0.00 ± 0.31 (T_maxR) and −0.05 ± 0.40 (T_maxL). The weighted Fleiss’ kappa coefficient for the T_1/2 assessments ranged between 0.85–0.97 for both intra- and inter-observer repeatability with both methods. These findings suggest a very good repeatability in DRF assessment with the manual method—especially for the experienced observer—but a less good repeatability with the semi-automated approach. The calculation of T_max was also operator-dependent. We conclude that reader experience is important in the calculation of renal parameters. We therefore encourage reader training in renal scintigraphy. Moreover, the manual tool seems to perform better than the semi-automated tool. Thus, we encourage cautious use of automated tools and adjunct validation by manual methods where possible.

COMPARATIVE RENAL DISPOSITION OF CREATINE, AND TECHNETIUM DIAGNOSTIC CONTRAST AGENTS IN THE PIGEON (COLUMBA LIVIA)

Clinical assessment of renal function in avian species often involves the measurement of plasma uric acid and blood urea nitrogen, relatively insensitive markers of renal dysfunction and dehydration. In mammals, endogenous creatinine is widely used as an indicator of renal glomerular dysfunction. However, avian species produce primarily creatine. Here, renal creatine, ^99mTc99-DTPA (diethylenepentaacetic acid, DTPA) and 99mTc-MAG3 (mercaptoacetyl triglycine, MAG₃) renal clearances are characterized in the pigeon avian model by infusing DTPA with inulin and creatine with each tracer and examining the slope of their blood disappearance curves. Clearance curves for inulin and DTPA were parallel, suggesting DTPA is cleared by renal filtration. MAG₃ clearance (slope: -2.74 × 10⁵, r² = 0.97) had a slope almost 10-fold steeper than for DTPA (slope: -6.29 × 10⁴, r² = 0.90), and orders of magnitude steeper than for creatine (slope: -1.4, r² = 1.0). These results suggest that DTPA is cleared by glomerular filtration like inulin, while MAG3 is filtered and actively excreted in a manner similar to mammals. In contrast, creatine is filtered and resorbed, has a larger volume of distribution (V_d), or exhibits a greater blood protein binding, making it more complex as a renal marker, when compared with creatinine handling in mammals. The two radiotracers can be readily adapted for use in birds, inviting both qualitative and semiquantitative functional evaluation of avian renal function for research and clinical purposes. The elimination of creatine appears to be more complex requiring further study.

Simplified Dynamic Phantom for Pediatric Renography: A Description of Instrument and its Performance

Objective(s):

Renography is used for the diagnostic evaluation of pediatric patients with a suspected obstruction of urinary tract or impaired renal function. The recommended dose for children have been released by the European Association of Nuclear Medicine, Society of Nuclear Medicine and Molecular Imaging, and Japanese Society of Nuclear Medicine. Since acquisition counts in dynamic scintigraphy are affected by the administered doses and sensitivity of the scintillation camera, the scan procedure should be determined independently.

In this study, we constructed simplified dynamic phantom imitating pediatric renography and tested its performance.

Methods:

Simplified dynamic phantom consisted of three components (i.e., infusion, imitated kidney, and drainage sections). The infusion rates (mL/min) were determined by comparing the time activity curves obtained from patients with normal renal function. The time-points of the maximum counts (T_max), as well as the two-thirds and one-half of the maximum counts (T_2/3 and T_1/2) were measured in different doses using the phantom with the best-match infusion rate and duration, and low-energy general-purpose (LEGP) or low-energy high-resolution (LEHR) collimators and applying different attenuations.

Results:

The best-match infusion rates of the phantom to imitate the time activity curve of the normal renal function were 42.0, 1.0, 0.6, and 0.3 mL/min in the arterial, secretory, early-excretory, and late-excretory phases, respectively. When 30 MBq, LEHR collimator and non-water-equivalent phantom were applied, T_max, T_2/3, and T_1/2 were 242±15.3, 220±10.0 and 317±25.2 seconds, respectively. Using LEGP collimator and (3 MBq of activity) 5-cm water-equivalent phantom, T_max, T_2/3, and T_1/2 values were estimated as 242±5.8, 213±11.5, and 310±17.3 sec, respectively.

Conclusion:

Our simplified dynamic phantom for pediatric renography could imitate the time activity curves obtained from patients with normal renal function. T_max, T_2/3, and T_1/2 could be measured under various settings of dose, collimator, and tissue attenuation.

A new two-strip TLC method for the quality control of technetium-99m mercaptoacetyl-triglycine (99mTc-MAG3)

Background

^99mTc-mercaptoacetyl-triglycine (^99mTc-MAG3) has been used for dynamic renal imaging since about 30 years. Free pertechnetate (^99mTcO₄), colloidal ^99mTc ((^99mTcO₂)_n), ^99mTc-tartrate (precursor), precomplexes (^99mTc-(MAG3)_x) and lipophilic ^99mTc-MAG2 are the main radiochemical impurities that may occur in the preparation. The total amount of these impurities has to be identified before release of the product for patient administration to guarantee patient safety and good image quality. The European Pharmacopoeia suggests a method based on high-pressure liquid chromatography analysis in combination with a paper chromatography. This analytical method is time consuming, expensive and requires specially trained technicians. As a consequence, it is not widely applied in nuclear medicine radiopharmacies.

Results

We developed a simple method for radiochemical purity testing of ^99mTc-MAG3. The method is based on thin layer chromatography with two strips to be developed in parallel. Method validation was carried out in comparison to the official methods of the companies and to the European Pharmacopoeia method. It was tested on specificity, accuracy, robustness and precision.

Conclusion

The proposed method is able to identify and quantify the sum of all impurities occurring in the preparation, respecting the acceptance criteria for the radiochemical purity defined by the official methods. Hydrophilic and lipophilic compounds are identified separately and results are obtained within less than 20 minutes. Our method is simple, cost effective, fast and is suitable for employing dose calibrators or radiometric scanners.

Electronic supplementary material

The online version of this article (10.1186/s41181-018-0040-5) contains supplementary material, which is available to authorized users.

Biokinetics, dosimetry, and radiation risk in infants after 99mTc-MAG3 scans

BACKGROUND

Renal scans are among the most frequent exams performed on infants and toddlers. Due to the young age, this patient group can be classified as a high-risk group with a higher probability for developing stochastic radiation effects compared to adults. As there are only limited data on biokinetics and dosimetry in this patient group, the aim of this study was to reassess the dosimetry and the associated radiation risk for infants undergoing 99mTc-MAG3 renal scans based on a retrospective analysis of existing patient data. Consecutive data were collected from 20 patients younger than 20 months (14 males; 6 females) with normal renal function undergoing 99mTc-MAG3 scans. To estimate the patient-specific organ activity, a retrospective calibration was performed based on a set of two 3D-printed infant kidneys filled with known activities. Both phantoms were scanned at different positions along the anteroposterior axis inside a water phantom, providing depth- and size-dependent attenuation correction factors for planar imaging. Time-activity curves were determined by drawing kidney, bladder, and whole-body regions-of-interest for each patient, and subsequently applying the calibration factor for conversion of counts to activity. Patient-specific time-integrated activity coefficients were obtained by integrating the organ-specific time-activity curves. Absorbed and effective dose coefficients for each patient were assessed with OLINDA/EXM for the provided newborn and 1-year-old model. The risk estimation was performed individually for each of the 20 patients with the NCI Radiation Risk Assessment Tool.

RESULTS

The mean age of the patients was 7.0 ± 4.5 months, with a weight between 5 and 12 kg and a body size between 60 and 89 cm. The injected activities ranged from 12 to 24 MBq of 99mTc-MAG3. The patients' organ-specific mean absorbed dose coefficients were 0.04 ± 0.03 mGy/MBq for the kidneys and 0.27 ± 0.24 mGy/MBq for the bladder. The mean effective dose coefficient was 0.02 ± 0.02 mSv/MBq. Based on the dosimetry results, an evaluation of the excess lifetime risk for the development of radiation-induced cancer showed that the group of newborns has a risk of 16.8 per 100,000 persons, which is about 12% higher in comparison with the 1-year-old group with 14.7 per 100,000 persons (all values are given as mean plus/minus one standard deviation except otherwise specified).

CONCLUSION

In this study, we retrospectively derived new data on biokinetics and dosimetry for infants with normal kidney function after undergoing renal scans with 99mTc-MAG3. In addition, we analyzed the associated age- and gender-specific excess lifetime risk due to ionizing radiation. The radiation-associated stochastic risk increases with the organ doses, taking age- and gender-specific influences into account. Overall, the lifetime radiation risk associated with the 99mTc-MAG3 scans is very low in comparison to the general population risk for developing cancer.

Radionuclides in nephrourology, part 1: Radiopharmaceuticals, quality control, and quantitative indices

Radionuclide renal scintigraphy provides important functional data to assist in the diagnosis and management of patients with a variety of suspected genitourinary tract problems, but the procedures are underutilized. Maximizing the utility of the available studies (as well as the perception of utility by referring physicians) requires a clear understanding of the clinical question, attention to quality control, acquisition of the essential elements necessary to produce an informed interpretation, and production of a report that presents a coherent impression that specifically addresses the clinical question and is supported by data contained in the report. To help achieve these goals, part 1 of this review covers information that should be provided to the patient before the scan, describes the advantages and limitations of the available radiopharmaceuticals, discusses quality control elements needed to optimize the study, summarizes approaches to the measurements of renal function, and focuses on recommended quantitative indices and their diagnostic applications. Although the primary focus is the adult patient, aspects of the review also apply to the pediatric population.

Efficacy of retroperitoneal laparoscopic ureterolithotomy for the treatment of large proximal ureteric stones and its impact on renal function. Springerplus. 2013;2:600. [PMID: 24294547 PMCID: PMC3833921 DOI: 10.1186/2193-1801-2-600]

PURPOSE

The purpose of this study was to evaluate the efficacy of retroperitoneal laparoscopic ureterolithotomy for the management of large proximal ureteric stones and the impact of this treatment on postoperative renal function.

METHODS

The data of 12 patients (7 men and 5 women; mean age, 68.5 ± 8.9 years) with large pyeloureteral junction (2 cases) and upper ureteral (10 cases) stones (25.3 ± 7.4 mm) that had undergone retroperitoneal laparoscopic ureterolithotomy were reviewed. Renal function was analyzed by the estimated glomerular filtration rate (eGFR) and renal scintigraphy using 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) before and 3 months after surgery.

RESULTS

The mean operative time was 129.5 ± 21.4 minutes, with a mean blood loss of 64.4 ± 78.2 mL. The mean duration of hospital stay after surgery was 6.4 ± 2.7 days, and the mean duration of stenting was 7.2 ± 1.7 weeks. A stone clearance rate of 100% was achieved, and no patient developed ureteric stricture. 99mTc-MAG3 scintigraphy showed that laparoscopic removal of calculi did not affect renal function, but did improve ureteral occlusion.

CONCLUSIONS

Retroperitoneal laparoscopic ureterolithotomy is a safe and effective treatment option for reducing ureteral obstruction in select patients with large proximal ureteric stones.

Effect of the NSAID diclofenac on 99mTc-MAG3 and 99mTc-DTPA renography

Renal function and disease are commonly evaluated by radionuclide studies. The choice of radiopharmaceutical agent for various studies is crucial for proper interpretation. (99m)Tc-mercaptoacetyltriglycine ((99m)Tc-MAG3) is excreted almost exclusively by the renal tubules, whereas (99m)Tc-diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) is predominantly excreted by glomerular filtration. The present study compared the effect of the nonsteroidal antiinflammatory drug (NSAID) diclofenac, which is the most commonly used drug to relieve kidney pain, on the kinetic behavior of administered (99m)Tc-MAG3 and (99m)Tc-DTPA in experimental animals.

METHODS

Two groups of 12 New Zealand White rabbits ((99m)Tc-MAG3 and (99m)Tc-DTPA) were used for the renography. Each rabbit served as its own control. The animals were given 60 mL of saline intravenously 30 min before each renographic study. A baseline study (control) was done by injecting 48 MBq (1.3 mCi) of (99m)Tc-MAG3, and renography was performed. Two days later, a single intravenous dose of diclofenac (2 mg/kg) (treated animals) was given, and after 20 min, (99m)Tc-MAG3 renography was performed. This procedure was repeated for the (99m)Tc-DTPA group after administration of 96 MBq (2.6 mCi) of the tracer. Dynamic images (as 2-s frames for the first minute and 30-s frames for the next 30 min on a 64 × 64 matrix) were acquired using a γ-camera equipped with a low-energy high-resolution collimator interfaced with a computer. Regions of interest were drawn over the whole kidneys. Time-activity curves were generated from the region of interest. Time to peak activity (T(max)), time from peak to 50% activity (T(1/2)), and the uptake slope of each kidney were calculated from the renograms for control and treated rabbits.

RESULTS

Administration of diclofenac shifted the experimental renogram curves to the right, compared with the control curves, indicating that there was a delayed renal uptake of the 2 tracers and clearance of the radioactivity. The calculated average values of T(max) for control and treated rabbits using (99m)Tc-MAG3 were 1.8 ± 0.5 and 6.35 ± 0.4 min, respectively, whereas those of (99m)Tc-DTPA were 3.4 ± 0.4 and 18.2 ± 2 min, respectively. The T1/2 for control and treated rabbits for (99m)Tc-MAG3 were 3.2 ± 0.07 and 6.6 ± 0.07 min, respectively, whereas those for (99m)Tc-DTPA were 10.1 ± 1 and 35 ± 4 min, respectively. The differences were statistically significant (P < 0.05).

CONCLUSION

This study showed that diclofenac delayed both T(max) and T1/2. The NSAID-induced kinetic changes were considerably greater for (99m)Tc-DTPA than for (99m)Tc-MAG3. On the basis of these findings, it is suggested that (99m)Tc-MAG3 be used to perform renography for studies involving the use of NSAID administration to decrease any change that may occur due to the type of tracer and not to the condition of the kidney.

The diagnosis of yo-yo reflux with dynamic renal scintigraphy in a patient with incomplete ureteral duplication

The diagnosis of yo-yo reflux in patients with incomplete upper collecting system duplications is difficult. We report a case with recurrent urinary tract infections and ultrasonographically detected duplication in the left collecting system in which the presence of yo-yo reflux is demonstrated with dynamic renal scintigraphy.

Conflict of interest:None declared.