The conundrum of high-grade hydronephrosis with non-obstructive drainage on diuretic renography.

BACKGROUND: Patients with high grade hydronephrosis (HN) and non-obstructive drainage on mercaptoacetyltriglycine (MAG-3) diuretic renography (renal scans) can pose a dilemma for clinicians. Some patients may progress and require pyeloplasty; however, more clarity is needed on outcomes among these patients. OBJECTIVE: Our primary objective was to predict which patients with high-grade HN and non-obstructive renal scan, (defined as T ½ time <20 min) would experience resolution of HN. Our secondary objective was to determine predictors for surgical intervention. STUDY DESIGN: Patients with prenatally detected HN were prospectively enrolled from 7 centers from 2007 to 2022. Included patients had a renal scan with T ½<20 min and Society for Fetal Urology (SFU) grade 3 or 4 at last ultrasound (RBUS) prior to renal scan. Primary outcome was resolution of HN defined as SFU grade 1 and anterior posterior diameter of the renal pelvis (APD) < 10 mm on follow-up RBUS. Secondary outcome was pyeloplasty, comparing patients undergoing pyeloplasty with patients followed with serial imaging without resolution. Multivariable logistic regression was used for analysis. RESULTS: Of the total 2228 patients, 1311 had isolated HN, 338 patients had a renal scan and 129 met inclusion criteria. Median age at renal scan was 3.1 months, 77% were male and median follow-up was 35 months (IQR 20-49). We found that 22% (29/129) resolved, 42% of patients had pyeloplasty (54/129) and 36% had persistent HN that required follow-up (46/129). Univariate predictors of resolution were age≥3 months at time of renal scan (p = 0.05), T ½ time≤5 min (p = 0.09), SFU grade 3 (p = 0.0009), and APD<20 mm (p = 0.005). Upon multivariable analysis, SFU grade 3 (OR = 4.14, 95% CI: 1.30-13.4, p = 0.02) and APD<20 mm (OR = 6.62, 95% CI: 1.41-31.0, p = 0.02) were significant predictors of resolution. In the analysis of decision for pyeloplasty, SFU grade 4 (OR = 2.40, 95% CI: 1.01-5.71, p = 0.04) and T ½ time on subsequent renal scan of ≥20 min (OR = 5.14, 95% CI: 1.54-17.1, p = 0.008) were the significant predictors. CONCLUSIONS: Patients with high grade HN and reassuring renal scan can pose a significant challenge to clinical management. Our results help identify a specific candidate for observation with little risk for progression: the patient with SFU grade 3, APD under 20 mm, T ½ of 5 min or less who was 3 months or older at the time of renal scan. However, many patients may progress to surgery or do not fully resolve and require continued follow-up.

99m Tc-DTPA dynamic SPECT/CT renogram in adults: feasibility and diagnostic benefit.

OBJECTIVE: The objective of this study is to investigate the feasibility and potential advantages of 99m Tc-DTPA dynamic single photon emission computed tomography/computed tomography (SPECT/CT) renogram in adults. METHODS: Fifty-five patients aged 19-80 years (mean 56.3) were enrolled. The imaging protocol included: day 1: 99m Tc-DTPA planar renogram, followed by planar 99m Tc-DMSA scan. Day 3: attenuation-corrected dynamic 99m Tc-DTPA SPECT renogram [DSPECT(AC)] and Cr-51 ethylenediamine tetraacetic acid (EDTA) glomerular filtration rate (GFR) calculation. DSPECT(AC) included an initial CT scan followed by 12 consecutive SPECT sessions acquired via continuous-mode acquisition for a total of 24 min. Fast SPECT sequences (1-2 s/projection, 60 projections, every 6°) were obtained for the first 8 min, followed by slower acquisitions (3-4 s/projection) during the rest of the study. Renal activity was measured in the total kidney volume by regions of interest drawn on consecutive transaxial slices of the third SPECT, which were then copied on the whole 12-SPECT series. Corresponding time-activity curves were created. DSPECT(AC) parameters were compared with those of planar renogram. The reference method for split renal function was 99m Tc-DMSA (geometrical mean of anterior and posterior projection counts) and for GFR the Cr-51 EDTA 2-blood sample clearance method. RESULTS: DSPECT(AC) images were of good quality. There was good correlation between renogram parameters (time to peak activity and NORA20) comparing the two techniques ( r  = 0.959 and 0.933, respectively). In 21 cases with >30% absolute difference between the two kidneys, spilt renal function calculation by DSPECT(AC) correlated perfectly ( r  = 0.968) with the reference method, whereas planar renogram was less accurate ( r  = 0.843). Anatomic information provided by nonenhanced CT offered an integrated structural-functional view valuable for final diagnosis. DSPECT(AC) early kidney uptake as a fraction of injected dose correlated better with reference GFR ( r  = 0.789) than the Gates' method ( r  = 0.642). CONCLUSION: 99m Tc-DTPA dynamic SPECT/CT renogram is feasible with conventional SPECT/CT systems. It allows accurate split renal function measurement, offers additional anatomical information and can be used for closer approximation of GFR compared with Gates' method.

Noninvasive measurement of tracer extraction efficiency in tissue, illustrated with Tc-99m-MAG3.

OBJECTIVE: The aim of this study is to develop a noninvasive technique for measuring tissue tracer extraction efficiency ( E ) and illustrate it for Tc-99m-mercaptoacetyltriglycine (MAG3) and kidney. METHODS: E was measured in 10 patients with normal MAG3 renography. E is the ratio of tissue clearance-to-blood flow ( Ki/F ). For single-photon tracers, attenuation constants are unknown, so Ki and F cannot be separately measured. However, by deriving attenuation-uncorrected Ki' and F' from the same regions of interests (ROIs), these constants cancel out, giving E . Using a lung ROI for blood activity, F was measured from first-pass and Ki' from Gjedde-Patlak-Rutland (GPR) analysis up to 130 s. Because of interference from right ventricle, a left ventricular ROI (LV) is unsuitable for F' but was used in GPR analysis, making an adjustment for the ratio of respective blood pool signals arising from lung and LV ROIs in early frames (60-90 s). RESULTS: A lung ROI underestimates F' by 4% at normal LV function. Chest wall interstitial activity ( I ), which does not affect F' , amounted to 53 and 30% of the lung and LV signals at 20 min, and 12 and 6% at 130 s, resulting in underestimations of Ki of 4 and 2%, respectively. Ignoring these opposing errors, E based on lung ROI for left and right kidneys was 43.5 (SD 8)% and 47.3 (9)%, and based on LV ROI for GPR analysis was 44.5 (10.9)% and 48.3 (10.6)%. CONCLUSION: E can be measured by combining blood flow from first-pass with clearance from GPR analysis, and has potential value both clinically and in clinical research.

Integrated Diffusion Tensor Imaging and Renal Parenchymal Volume for Early Detection and Grading of Split Renal Functional Impairment in Lupus Nephritis.

RATIONALE AND OBJECTIVES: To investigate the effectiveness of combining split diffusion tensor imaging (DTI) measurements with split renal parenchymal volume (RPV) for assessing split renal functional impairment in patients with lupus nephritis (LN). MATERIALS AND METHODS: Seventy-four participants [48 LN patients and 26 healthy volunteers (HV)] were included in the study. All participant underwent conventional MR and DTI (b = 0, 400, and 600 s/mm2) examinations using a 3.0 T MRI scanner to determine the split renal DTI measurements and split RPV. In LN patients, renography glomerular filtration rate (rGFR) was measured using 99mTc-DTPA scintigraphy based on Gates' method, serving as the reference standard to categorize all split kidneys of LN patients into LN with mild impairment (LNm, n = 65 kidneys) and LN with moderate to severe (LNms, n = 31 kidneys) groups according to the threshold of 30 ml/min in spilt rGFR. All statistical analyses were performed using SPSS 25.0 and MedCalc 20.0 software packages. RESULTS: Only split medullary fractional anisotropy (FA) and the product of split medullary FA and RPV could distinguish pairwise subgroups among the HV and each LN subgroup (all p < 0.05). ROC curve analysis demonstrated that split medullary FA (AUC = 0.866) significantly outperformed other parameters in differentiating HV from LNm groups, while the product of split medullary FA and split RPV was superior in distinguishing LNm and LNms groups (AUC = 0.793) than other parameters. The combination of split medullary FA and split RPV showed best correlation with split rGFR (r = 0.534, p < 0.001). CONCLUSION: Split medullary FA, and its combination with split RPV, are valuable biomarkers for detecting early functional changes in renal alterations and predicting disease progression in patients with LN.

CT volumetry performs better than nuclear renography in predicting estimated renal function one year after living donation.

The evaluation of split renal function (SRF) is a critical issue in living kidney donations and can be evaluated using nuclear renography (NR) or computerized tomography (CT), with unclear comparative advantages. We conducted this retrospective study in 193 donors to examine the correlation of SRF assessed by NR and CT volumetry and compared their ability to predict remaining donor renal function at 1 year, through multiple approaches. A weak correlation between imaging techniques for evaluating the percentage of the remaining kidney volume was found in the global cohort, with an R2 = 0.15. However, the Bland-Altman plot showed an acceptable agreement (95% of the difference between techniques falling within - 8.51 to 6.11%). The predicted and observed eGFR one year after donation were calculated using the CKD-EPI, and CG/BSA equations. CT volume showed a better correlation than NR for both formulas (adjusted R2 of 0.42. and 0.61 vs 0.37 and 0.61 for CKD-EPI and CG/ BSA equations, respectively). In non-nested modeling tests, CT volumetry was significantly superior to NR for both equations. CT volumetry performed better than NR in predicting the estimated renal function of living donors at 1-year, independently from the eGFR equation.

Clues for the early loss of renal function in congenital hydronephrosis: Analysis of renal pelvis collagen ratio, diuresis renography and upper urinary tract morphology.

INTRODUCTION: Diagnosing real urinary obstruction and surgical decision making for the operative correction of urinary obstruction, are still problematic in congenital hydronephrosis (CH). Compliance of the renal pelvis is one of the important defense mechanisms of renal parenchyma against urinary obstruction. We observed early loss of function in some cases of CH with low and moderate anteroposterior diameter of the renal pelvis (APDRP). OBJECTIVE: To evaluate structural properties of the renal pelvic tissue of patients with CH and the relation of these structural properties with renal function and Anteroposterior diameter of the renal pelvis. STUDY DESIGN: Ureteropelvic junction (UPJ) excised during UPJ obstruction operations from 2013 to 2019 were evaluated histopathologically. The patients were divided into the two groups according to initial renal function, i.e. group with initial preoperative differential renal function (DRF) less than 35% and group with initial DRF greater than 35%. The percentage of collagen to whole tissue area were analyzed using image processing program. The relationship between DRF and tissue collagen ratio, SFU and APDRP was evaluated. RESULTS: There were 5 patients in the DRF <35% group and 16 patients in the DRF >35% group. However, APDRP's of the DRF <35% group were also significantly lower than the DRF >35% group. The collagen distribution in the muscle layer was more prominent in the DRF <35% group. Proportionally, percentage of collagen stained surface was significantly higher in DRF <35% group. DISCUSSION: There are numerous histopathological studies evaluating the cause of UPJ obstruction. Besides these studies that are oriented to etiology, there are many studies comparing the histopathological changes at UPJ with surgical outcome and prognosis. In the present study, we found that renal pelvis collagen ratio was significantly increased in patients with lower APDRP and with severe renal function loss. This increase in the collagen content in the renal pelvis have been shown to affect the compliance negatively and decrease APDRP, which leads to a faster loss of renal function. Thus, pelvic structural changes accompanying UPJ obstruction may aggravate urinary obstructive process. CONCLUSION: Increased renal pelvis collagen ratio negatively affects the expansion of the renal pelvis, which is one of the protective mechanisms of the renal parenchyma, and may be one of the triggering mechanisms of early loss of renal function.

Deep regression using 99mTc-DTPA dynamic renal imaging for automatic calculation of the glomerular filtration rate.

OBJECTIVES: To develop and evaluate an artificial intelligence (AI) system that can automatically calculate the glomerular filtration rate (GFR) from dynamic renal imaging without manually delineating the regions of interest (ROIs) of kidneys and the corresponding background. METHODS: This study was a single-center retrospective analysis of the data of 14,634 patients who underwent 99mTc-DTPA dynamic renal imaging. Two systems based on convolutional neural networks (CNN) were developed and evaluated: sGFRa predicts the radioactive counts of ROIs and calculates GFR using the Gates equation and sGFRb directly predicts GFR from dynamic renal imaging without using other information. The root-mean-square error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), and R2 were used to evaluate the performance of our approach. RESULTS: sGFRa achieved an RMSE of 5.05, MAE of 4.03, MAPE of 6.07%, and R2 of 0.93 for total GFR while sGFRb achieved an RMSE of 7.61, MAE of 5.92, MAPE of 8.92%, and R2 of 0.85 for total GFR. The accuracy of sGFRa and sGFRb in determining the stage of chronic kidney disease was 87.41% and 82.44%, respectively. CONCLUSIONS: The findings of sGFRa show that automatic GFR calculation based on CNN and using dynamic renal imaging is feasible and efficient and, additionally, can aid clinical diagnosis. Furthermore, the promising results of sGFRb demonstrate that CNN can predict GFR from dynamic renal imaging without additional information. KEY POINTS: • Our CNN-based AI systems can automatically calculate GFR from dynamic renal imaging without manually delineating the ROIs of kidneys and the corresponding background. • sGFRa accurately predicted the radioactive counts of ROIs and calculated GFR using the Gates method. • sGFRb-predicted GFR directly without any parameters related to the Gates equation.

Initial observational management of hydronephrosis in infants with reduced differential renal function and non-obstructive drainage parameters.

INTRODUCTION: Hydronephrosis secondary to ureteropelvic junction (UPJ) obstruction is a common finding in infants with prenatally-diagnosed hydronephrosis and often results in pyeloplasty due to obstructive drainage parameters and/or renal function compromise. However, little is known regarding the natural history of hydronephrosis with reduced differential renal function (DRF) but non-obstructive drainage. OBJECTIVE: We sought to explore our experience with initial observational management of these patients. STUDY DESIGN: A retrospective review of our institutional database of all diuretic MAG-3 renal scans obtained between 2000 and 2016 was performed. We included patients with antenatally-detected unilateral hydronephrosis ≥ SFU grade 2, first MAG-3 scan prior to 18months of age, DRF <40% and post-furosemide half-time (T1/2) <20 min. Exclusion criteria were: hydroureter, VUR, solitary kidney, duplication anomalies. Outcomes of interest were a progression of T1/2 ≥ 20 min and/or further decline in DRF >5%. RESULTS: Of 704 patients with unilateral hydronephrosis, 91 had DRF≤40%, of which 29 (18 boys, 11 girls) met our inclusion criteria and were followed for a mean of 2.8 years (1.4 months-6.6 years). Mean age at first sonogram was 2.3 months. 2 patients had SFU grade 2, 16 had grade 3, and 9 had grade 4 hydronephrosis, and 2 unknown grade. Median half-time on initial MAG-3 scan across all patients was 10 min (3-20 min). Initial MAG3 scan was performed at a median of 2.3 months of age (0.3-17 months). 22/29 patients had >1 MAG3 scan. Of the 7 remaining, 5 were lost to follow-up and 2 demonstrated improvement in hydronephrosis. Worsening drainage occurred in 10/22(45%), median final T1/2 was 45.5 min 8 of these underwent pyeloplasty and 2 were lost to follow up. 4/22 patients (18%) had progressive decline in DRF (mean 8.3%, range 6-10%). 3/4 maintained non-obstructive drainage patterns and stable/improved hydronephrosis, and 1 underwent pyeloplasty. 13/18 remaining patients had stable DRF and 5 had improvement in DRF. 7(39%) of these underwent surgery for worsening drainage (Summary Figure). Overall, 7/29(24%) patients had sufficient resolution of hydronephrosis to be discharged from our care, 8(28%) are under continued observation, 9(31%) underwent pyeloplasty, and 5(17%) were lost to follow-up. In the observational group [median follow-up 4.5 years (3.7-6.6 years)], all 8 demonstrated improved non-obstructive drainage (T1/2 <20 minutes) and/or improvement in hydronephrosis. 4/10(40%) with DRF <35% underwent pyeloplasty versus 5/19(26%) with DRF 35-40%(p=0.67). CONCLUSION: Initial observational management of unilateral hydronephrosis with reduced DRF and nonobstructive drainage is recommended as most kidneys maintain nonobstructive drainage and do not demonstrate further decline in DRF. Even when DRF decreases, the majority remain non-obstructive. Worsening drainage over time more often leads to the decision for pyeloplasty rather than change in DRF.

Comparison of CT volumetry versus nuclear renography for predicting remaining kidney function after uninephrectomy in living kidney donors.

Computed tomography (CT) and nuclear renography are used to determine kidney procurement in living kidney donors (LKDs). The present study investigated which modality better predicts kidney function after donation. This study included 835 LKDs and they were divided into two subgroups based on whether the left-right dominance of kidney volume was concordant with kidney function (concordant group) or not (discordant group). The predictive value for post-donation kidney function between the two imaging modalities was compared at 1 month, 6 months, and > 1 year in total cohort, concordant, and discordant groups. Split kidney function (SKF) measured by both modalities showed significant correlation with each other at baseline. SKFs of remaining kidney measured using both modalities before donation showed significant correlation with eGFR (estimated glomerular filtration rate) after donation in the total cohort group and two subgroups, respectively. CT volumetry was superior to nuclear renography for predicting post-donation kidney function in the total cohort group and both subgroups. In the discordant subgroup, a higher tendency of kidney function recovery was observed when kidney procurement was determined based on CT volumetry. In conclusion, CT volumetry is preferred when determining procurement strategy especially when discordance is found between the two imaging modalities.

Pediatric Nephro-Urology: Overview and Updates in Diuretic Renal Scans and Renal Cortical Scintigraphy.

Nuclear medicine offers several diagnostic scans for the evaluation of congenital and acquired conditions of the kidneys and urinary track in children. Tc-99m-MAG 3 diuretic renal scans are most commonly used in the evaluation and follow up of urinary track dilatations. They provide functional information on the differential renal function and on drainage quality which is allows distinction between obstructed and non-obstructed kidneys and the need for surgical correction vs conservative management in kidneys with impaired drainage. Standardized imaging and processing protocols are essential for correct interpretation and for meaningful comparisons between follow up scans. Different approaches and conceptions led to some contradicting recommendations between SNMMI and EANM guidelines on diuretic renography in children which caused confusion and to the emergence of self-made institutional protocols. In Late 2018 the two societies published joint procedural guidelines on diuretic renography in infants and children which hopefully will end the confusion. Tc-99m DMSA scans provide important information about the function of the renal cortex allowing detection of acute pyelonephritis, renal scars dysplasia and ectopy as well as accurate determination of the differential renal function. They are commonly used in the evaluation of children with urinary tract infections and affect clinical management. A standardized imaging and processing protocol improves the diagnostic accuracy of these studies. SPECT or pinhole images should be a routine part of the imaging protocol. This is one of the recommendations in the new EANM and SNMMI procedural guidelines for renal cortical scintigraphy in children available online on the SNMMI website and is under publication. This article provides an overview on the clinical role of diuretic renography and cortical scintigraphy in children and describes the imaging protocols focusing on the new recommendations in the procedural guidelines.

Diuretic Renal Scintigraphy in Adults: Practical Aspects and Reporting.

Diuretic renal scintigraphy (DRS) is used worldwide for evaluation of kidney functions, diagnosis of pelvic or ureteric obstruction and documentation of the effectiveness of surgical interventions. Although it is a basic imaging procedure of nuclear medicine, there is a wide range of variability in acquisition procedures. Nuclear medicine physicians have the opportunity to modify DRS imaging protocols according to specific clinical problem or question. This plasticity requires readers experience. Interpretation of dynamic images and the quantitative parameters entails knowledge of physiology and pathophysiology of kidneys and collective system. Standardization of patient preparation, imaging protocols and reporting not only would increase the readers' confidence but also would increase the reliability of DRS.

Renography with a semiautomated algorithm for diuretic decision 7 min postradiopharmaceutical administration: a feasibility study.

OBJECTIVE: The F+10 method for diuretic renography (diuretics given 10 min after the radiopharmaceutical) could be a time-conserving method. This method involves a 30-min dynamic acquisition where diuretics are administered only when necessary by the Nuclear Medicine technologist performing the examination. The purpose of this study was to assess the method's performance and to discover the optimal threshold of residual activity for a diuretic administration 7 min into the F+10 renography by reprocessing raw data from prior performed examinations with 20-min acquisitions without diuretics. METHODS: Retrospectively, raw data from 320 original examinations of adult patients performed from 2013 to 2015 were reprocessed into 7-min series and categorized as requiring diuretic or not. The diuretic decisions made by an expert panel were used as a reference. A receiver-operating characteristic curve was drawn to assess the optimal cutoff value for the residual renal activity. Sensitivity, specificity, positive and negative predictive values, as well as the Youden J index were calculated. RESULT: The experts classified 50% (160 examinations) as in need of diuretics. The receiver-operating characteristic curve demonstrated the theoretical optimal cutoff value at 7 min to be 94% of maximum activity (sensitivity 0.93, specificity 0.81, Youden J index 0.73). A clinically acceptable threshold is suggested to be 85% (sensitivity 0.99, specificity 0.59, Youden J index 0.58). CONCLUSION: Tc-mercaptoacetyltriglycine renography with the F+10 method and the threshold 85% for diuretic decision 7 min into the renography is a feasible and acceptable method in clinical practice.

99mTc-mercaptoacetyltriglycine Cortical Renography Predicts Outcomes in Adult Living Donor Renal Transplant Recipients.

BACKGROUND: The clinical utility of 99mTc-mercaptoacetyltriglycine cortical renography for the prediction of graft function in kidney transplant recipients has been unknown. METHODS: We retrospectively reviewed post-transplant cortical renograms in 40 kidney transplant recipients. We analyzed the correlation between T1/2 (elimination half-life) and graft function (measured-to-expected glomerular filtration rate [GFR]) 1 week, and 1, 3, and 6 months post operation compared with whole-kidney renograms. RESULTS: Delayed drainage (T1/2 > 11 minutes) was observed in 22 recipients (55%). T1/2 and postoperative GFR ratio were inversely correlated (1 week: R2 = 0.317, P = .0002; 1 month: R2 = 0.206, P = .003; 3 months: R2 = 0.117, P = .031; 6 months: R2 = 0.161, P = .010). Recipients with delayed drainage had a significantly lower GFR ratio than those with normal drainage 1 week (median, 0.93 vs 1.32; P = .001), 1 month (median, 1.65 vs 2.23; P = .0010), 3 months (median, 1.55 vs 2.17; P = .041), and 6 months (median, 1.67 vs 2.34; P = .018) post operation, respectively. Whole-kidney renograms failed to discriminate recipients with lower GFR ratio at 1, 3, and 6 months. CONCLUSIONS: T1/2 in post-transplant cortical renography was inversely correlated with early graft function and may predict early post-transplant graft function.

Glomerular filtration rate: comparison of simultaneous plasma clearance of 99mTc-DTPA and 51Cr-EDTA revisited.

The issue of whether 99mTc-DTPA can replace 51Cr-EDTA for measurement of plasma clearance as a surrogate for glomerular filtration rate (GFR) is of great relevance to daily clinical practice. Prompted by the shortage of 51Cr-EDTA we conducted a head-to-head comparison in patients attending our department for GFR determination. The two tracers (3.7 MBq of 51Cr-EDTA and 8 MBq of 99mTc-DTPA) were administered intravenously immediately after each other, and the standard number of blood samples were drawn. Fifty-four patients were enrolled. In 51 of these, single-sample measurement was performed with the following results: GFREDTA was 84.6 ± 23.3 mL/min, GFRDTPA was 84.2 ± 24.7 mL/min. The mean difference was 0.4 ± 2.8 mL/min, p = 0.32, and results based on the two tracers were highly correlated (r = 0.995). GFRDTPA exceeded GFREDTA at high GFR values (difference < 0 at GFREDTA >91.4 mL/min) and vice versa (difference > 0 at GFREDTA < 91.4 mL/min). However, differences fell within few GFR units that most often will have no clinical consequence. We therefore conclude that 99mTc-DTPA can replace 51Cr-EDTA for single-sample determination of GFR in a clinical setting.

Ureterocolic fistula detected by mercaptoacetyltriglycine (MAG-3) diuretic renography including single photon emission CT and low-dose CT (SPECT-CT).

We describe the case of a 60-year-old man with a ureterocolic fistula following laparoscopic sigmoid resection. The fistulous tract between the left ureter and sigmoid colon was detected by mercaptoacetyltriglycine diuretic renography including single photon emission CT with low-dose CT. Ureteroneocystostomy was successfully performed.

Comparison of simultaneous plasma clearance of 99mTc-DTPA and 51Cr-EDTA: can one tracer replace the other?

Both 99mTc-DTPA and 51Cr-EDTA are widely used to determine glomerular filtration rate (GFR), but few direct comparative studies exist. The shortage of 51Cr-EDTA makes a direct comparison highly relevant. The aim of the study was to investigate if there is any clinically relevant difference between plasma clearance of 99mTc-DTPA and 51Cr-EDTA. Patients ≥18 years of age referred for routine GFR measurement by 51Cr-EDTA were prospectively enrolled. The two tracers (10 MBq 99mTc-DTPA (CaNa3-DTPA) and 2.5 MBq 51Cr-EDTA) were intravenously injected at time zero. A standard 4-sample technique was applied with samples collected at 180, 200, 220 and 240 min, if the estimated GFR (eGFR) was ≥30 mL/min. A comparison of single-sample GFR based on the 200 min sample was also conducted. Fifty-six patients were enrolled in the study. All patients had an estimated GFR >30 mL/min/1.73 m2. No patients suffered from ascites or significant oedema. The mean 51Cr-EDTA plasma clearance was 82 mL/min (range 16-226). The plasma clearances determined by the two methods were highly correlated (r = 0.993). The plasma clearance was significantly higher when measured by 99mTc-DTPA than by 51Cr-EDTA (p = 0.01), but the numerical difference was minimal (mean difference 1.4 mL/min; 95% limits of agreement (LOA) -6.6 to 9.4). The difference between the two methods was independent of the level of renal function. Similar results were found for one-sample GFR. No clinically relevant differences were found between the plasma clearance of 99mTc-DTPA and that of 51Cr-EDTA. Therefore, 99mTc-DTPA can replace 51Cr-EDTA when needed.

Successful paediatric renography does not require sedation.

INTRODUCTION: Sedation is often used to optimise ren-ography in children < 3 years, but it requires continuous monitoring. METHODS: We discontinued routine use of chloral hydrate sedation of patients undergoing renography, and introduced that children < 2 years were placed in a child immobiliser for nuclear examinations at the Department of Paediatrics before being transported for renography. In addition, children < 3 years were offered melatonin, which is not a sedative. Chloral hydrate was given only if parents wanted sedation. We analysed the results from a consecutive series of patients undergoing renography from August 2010 to December 2015 and compared data from those who had been administered choral hydrate sedation with those who had received no sedation. RESULTS: Renography was unaccomplished in 10% (3/30) of the choral hydrated sedated children and in 11% (54/512) of the non-sedated children (p = 0.83). Uncooperative children resulted in failed renography in 0% (0/3) and 39% (21/54) of cases, respectively (p = 0.46). Patients placed in a child immobiliser at the Department of Paediatrics had the greatest probability of achieving successful renography (p = 0.0013), the shortest renography procedure duration irrespective of melatonin use (p = 0.0001) and the lowest risk of a procedure duration > 60 minutes (p = 0.0004). CONCLUSIONS: Renography can be performed without sedation. We recommend that children < 2 years be placed in a child immobiliser at the Department of Paediatrics before being transported for renography. Additional studies are needed to investigate the effects of melatonin. FUNDING: none. TRIAL REGISTRATION: not relevant.

Diuresis renography in the evaluation and management of pediatric hydronephrosis: What have we learned?

Diuresis renography (DR) is widely used in the evaluation of hydronephrosis and hydroureter in infants and children. The goal of this provocative nuclear imaging examination should be to detect the hydronephrotic kidneys at risk for loss of function and development of pain, hematuria, and urinary tract infection. The reliability of DR is dependent on the acquisition and processing of the data as well as interpretation and utilization of the results. In this review, the key concepts of standardized DR and pitfalls to avoid are highlighted.

Effect of Verapamil on Kidney Function Using Radionuclide Imaging.

BACKGROUND AND OBJECTIVE: Calcium channel blockers (CCBs) are among the most widely used prescribed drugs for the treatment of cardiovascular diseases. The present study investigates the effect of verapamil, which is most commonly used as a CCB, on kidney function using radionuclide imaging. METHODS: Ten New Zealand white rabbits were used in vitro (4) and in vivo (6) studies. Isometric tensions were recorded for isolated renal artery ring segments, while renographic studies were performed using Technetium-99m mercaptoacetyltriglycine and Gamma camera. Time to peak activity (Tmax) and time from peak to 50% activity (T1/2), were calculated from the renograms for control and treated rabbits with verapamil. RESULTS: In vitro, verapamil shifted the curve of phenylephrine concentration-dependent contraction on renal artery to the right, and decrease the highest contraction by 30 ± 3%. In vivo, the average values of Tmax for control and treated rabbits were 2.8 ± 0.1 and 2.2 ± 0.2 min respectively. The T1/2 for control and treated rabbits were 4.7 ± 0.05 and 4.2 ± 0.08 min respectively. The differences were statistically significant: p < 0.05. There is 30 ± 4% decrease in the 2 values. This indicates that there is a rapid renal uptake of the tracer and clearance of the radioactivity after verapamil. CONCLUSION: Verapamil dilates the renal artery and accelerates both the Tmax and T1/2 in the renogram. It increases renal blood perfusion and protects kidney function and therefore improves its work. However, verapamil should not be used while performing renograms to avoid misleading results.