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.

Troubled but in good hands: A qualitative study on patient experiences in diuresis renography examinations.

INTRODUCTION: Diuresis renography is a nuclear medicine examination that can distinguish between obstructive and non-obstructive uropathy. Renography has been investigated before, but not from a patient perspective. The aim of this study was to gain knowledge and understanding of patient experiences with the diuresis renography process. METHODS: The study had a qualitative descriptive design; data was collected through semi-structured interviews with 17 adult patients that had recently undergone diuresis renography. The transcripts were analysed using inductive qualitative content analysis to identify their manifest and latent content. RESULTS: One main theme was identified: 'Not smooth all the way through, but still in good hands'. The participants understood the necessity of the performed renography and endured the examination despite its worrying elements. They were bothered by diuretic effects, worried about radioactivity and felt isolated during the imaging. The technologists' caring and informative approach eased their experience. The main theme was identified from three subthemes: 'I experienced inconvenience', 'I was worried' and 'I felt safe'. CONCLUSION: The participants experienced worry throughout the renography process but were still satisfied with the examination, mostly because of the technologists being involved. Communication and interaction between patient and technologist are important for creating a good experience. Improved knowledge of patient experiences during renographies could be used to develop patient information and increase technologists' awareness of factors patients may experience as troubling. IMPLICATIONS FOR PRACTICE: This study describes issues that contribute to both negative and positive experiences. Improved professional awareness and knowledge about these issues can contribute to the development of patient information and professional encounters, and may improve patients' compliance and overall experience.

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.

Nondiagnostic 99m Tc-MAG3 Diuresis Renography Studies Caused by Propofol Sedation : A Case Series.

ABSTRACT: 99m Tc-MAG3 diuresis renography is a noninvasive functional imaging technique used to assess clearance of radiotracer in a dilated urinary tract under high diuresis. It is commonly performed in patients to diagnose functionally significant urinary tract obstruction. In some pediatric patients, sedation is required to enable imaging. However, propofol, a commonly used IV sedative agent, is associated with altered renal hemodynamics. We report a case series of 3 pediatric patients at our institution who received propofol sedation to enable 99m Tc-MAG3 diuresis renography using a F+0 protocol, outlining that some "abnormal" studies were in fact assessed to be nondiagnostic.

Differential renal length index: useful measure in management of isolated unilateral hydronephrosis?

OBJECTIVE: To explore the usefulness of the 'differential renal length index' (iDRL) before and after pyeloplasty, as the anteroposterior diameter is commonly used to quantify hydronephrosis but inaccuracies arise due to interobserver variability, hydration status and pure intra-renal dilatation. PATIENTS AND METHODS: Prospectively collected data, from two centres, of all children undergoing pyeloplasty for isolated unilateral pelvi-ureteric junction obstruction (PUJO) (2015-2021) were analysed. Subgroup analysis was undertaken: Group A - differential renal function (DRF) ≥40%, Group B - subnormal DRF (20-39%), and Group C - symptomatic. Children with structural anomalies of upper and lower urinary tract, bilateral involvement, and subnormal DRF (<20%) were excluded. All the children had a pre- and postoperative ultrasound scan and Tc99m mercapto-acetyltriglycine (MAG3) renograms. The iDRL was calculated as follows: iDRL = ([a - b]/b) × 100, where 'a' is the length of hydronephrotic kidney (cm) and 'b' is the length of contralateral normal kidney (cm). The mean difference and standard error of mean (SEM) between the pre- and postoperative iDRL was evaluated using the paired Student's t-test, with P < 0.05 considered statistically significant. RESULTS: A total of 119 children with 1-year follow-up were included. For the entire cohort, the mean (SEM) preoperative iDRL was 27.7 (1.4) and postoperatively was 12.5 (1.1), with a mean (range) DRF improvement of 54% (44-66%) (P < 0.001). In Group A (n = 97), the mean (SEM) preoperative iDRL was 26.6 (1.5) and postoperatively was 13.1 (1.2), with a mean (range) DRF improvement of 50% (38-63%) (P < 0.001). In Group B (n = 22), the mean (SEM) preoperative iDRL was 32.6 (3.5) and postoperatively was 10.0 (2.8), with a mean (range) DRF improvement of 69% (49-89%) (P < 0.001). In Group C (n = 28), the mean (SEM) preoperative iDRL was 19.9 (2.3) and postoperatively was 7.7 (1.9), with a mean (range) DRF improvement of 61% (38-85%) (P < 0.001). CONCLUSION: Our study identifies the iDRL as a useful measure of improvement following successful pyeloplasty. In the subgroup with DRF of >39% minimum improvement was >37%. Similar minimum DRF improvement was also noted (>37%) in hypo-functioning kidneys and symptomatic PUJO.

Utility of F-15 diuretic MAG3 renography in assessment of paediatric hydronephrosis.

INTRODUCTION: Diuretic renography is crucial in evaluation of paediatric hydronephrosis. Furosemide is conventionally given 15-20 min after radiolabelled tracer (F+15/F+20 protocol), however this is equivocal in around 15% of patients. Giving furosemide 15 min prior to tracer (F-15 MAG3 protocol) has been suggested as an additional tool in the investigation of patients with suspected upper urinary tract obstruction. However, the role of this method in assessment and management of paediatric hydronephrosis is not widely reported. OBJECTIVE: To investigate utility of F-15 renograms in children with hydronephrosis being assessed for Pelvi-Ureteric Junction Obstruction (PUJO). STUDY DESIGN: Retrospective review of patients <16 years old undergoing F-15 MAG3 renogram between 2018 and 2021 in our tertiary paediatric surgical centre. Data collected included patient demographics, mode of presentation, investigations, management and outcomes. RESULTS: Eighteen patients were included. Median age at F-15 renogram was 7.3 years. Eleven patients presented with antenatal hydronephrosis, 5 with symptoms in childhood and 2 with incidental hydronephrosis on trauma imaging. Fourteen patients were symptomatic. Ten had a prior non-obstructed F+20 renogram but persisting symptoms suggestive of PUJO. Seven had previous equivocal F+20 renograms. One symptomatic patient directly underwent an F-15 renogram. A conclusive result was obtained in 16/18 (89%); 11 patients had obstructed curves and 5 non-obstructed. Two asymptomatic patients' scans were inconclusive. All symptomatic patients had conclusive scans. Of 11 patients with an obstructed F-15, 9 have undergone pyeloplasty to date. All have had post-operative resolution in symptoms and static or improved post-operative ultrasound. One patient with an inconclusive scan underwent pyeloplasty due to persisting hydronephrosis and parent preference. Three patients with non-obstructed F-15 renograms have been discharged. One symptomatic patient with a non-obstructive F-15 had a ureteric stent inserted due to persistent flank pain; 1 continues under surveillance. DISCUSSION: It is known that conventional F+20 MAG3 renograms can give equivocal results. Published experience suggests that F-15 renograms are conclusive in the majority of patients. Routine primary use is, however, discouraged as they can 'over diagnose' obstruction and limit the study of tracer transit under physiological flow rates. This study indicates that the F-15 renogram is a useful adjunct in the assessment of patients with symptoms suggestive of PUJO who have previously had an equivocal or a non-obstructed F+20 renogram. CONCLUSION: F-15 renogram was conclusive in 89% of patients. We recommend using F-15 renograms to aid surgical decision-making in children with equivocal F+20 renograms, especially in the presence of symptoms.

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.

Hydronephrotic lower moiety of duplex systems: Observations using diuresis renography.

PURPOSE: The purpose of this study is to characterize the prevalence and behavior of hydronephrosis of non-refluxing lower moiety of duplex kidneys using MAG-3 diuresis renography. We compare our data to previous case series and ureteropelvic junction obstruction of single systems. MATERIALS AND METHODS: An IRB-approved database of over 5000 diuresis renograms performed in 2025 patients was queried to identify cases of hydronephrosis of lower moiety of duplex kidneys suspicious for ureteropelvic obstruction, excluding those with hydroureter or reflux. Kidney function and post-furosemide drainage parameters on initial and follow-up diuresis renograms were recorded. Medical records and patient outcomes were reviewed. RESULTS: In total, 19 renal units were identified in 18 patients (11 male, 7 female), age range 0.5 months to 17.8 years, including one patient with bilateral lower moiety hydronephrosis. Initial diuresis renograms in 12 asymptomatic patients (13 renal units) with antenatal hydronephrosis demonstrated varying drainage patterns from normal to obstructed. Follow-up studies showed worsening drainage in 3 patients, who all underwent surgery. Drainage improved in 4 patients and remained unchanged in 5 patients (6 renal units). Of the 6 patients presenting with Dietl's crisis, 5 showed obstructive drainage on initial diuresis renogram, 2/5 with decreased function. All 5 obstructed patients underwent surgery. CONCLUSION: Hydronephrosis of the lower moiety of a duplex system is rare and behaves similarly to single systems. The majority are diagnosed antenatally, display a dynamic nature, and may present with acute obstruction. Diuresis renography is a valuable tool in its evaluation and management.

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.

Clearance While Upright on Initial Diuretic Renography Predicts the Need for Surgery in Children With Congenital Hydronephrosis.

OBJECTIVE: To improve the predictive ability of diuretic renography (DR) for surgical intervention in children with congenital hydronephrosis (CH) and concern for ureteropelvic junction obstruction. METHODS: Children with CH born between 2007 and 2021 who underwent initial DR prior to 6months of life, had both clearance while upright (CUP) and T ½ reported, and did not have immediate surgical intervention after the first DR were retrospectively evaluated for surgical intervention during the period of clinical observation. Once the optimal cut-points were identified for CUP and T ½, they were used to calculate the sensitivity, specificity, positive predictive value, and negative predictive value. RESULTS: In total 65 patients were included in the final analysis with 33 (50.8%) undergoing surgical intervention (pyeloplasty) and 32 (49.2%) still on observation at last follow-up. The optimal cut-points for predicting surgical intervention were 28.1 minutes for T ½ and 22.4% for CUP. Applying the CUP cut-point of 22.4% we achieved a sensitivity of 60.6% (95% CI: 43.9-77.3), specificity of 96.9% (95% CI: 90.1-100.0), positive predictive value of 95.2% (95% CI: 86.1-100.0), and negative predictive value of 70.5% (95% CI: 57.0-83.9). CONCLUSION: A low CUP accurately predicts surgical intervention in children with CH who are initially observed. Although there is no singular measure on DR that can with absolute certainty predict future clinical course, our data do suggest there is utility in incorporating CUP (if <22.4%) into the decision process. Further research is necessary to help guide the management of children with intermediate CUP values.

Predicting obstruction risk using common ultrasonography parameters in paediatric hydronephrosis with machine learning.

OBJECTIVE: To sensitively predict the risk of renal obstruction on diuretic renography using routine reported ultrasonography (US) findings, coupled with machine learning approaches, and determine safe criteria for deferral of diuretic renography. PATIENTS AND METHODS: Patients from two institutions with isolated hydronephrosis who underwent a diuretic renogram within 3 months following renal US were included. Age, sex, and routinely reported US findings (laterality, kidney length, anteroposterior diameter, Society for Fetal Urology [SFU] grade) were abstracted. The drainage half-times were collected from renography and stratified as low risk (<20 min, primary outcome), intermediate risk (20-60 min), and high risk of obstruction (>60 min). A random Forest model was trained to classify obstruction risk, here named the 'Artificial intelligence Evaluation of Renogram Obstruction' (AERO). Model performance was determined by measuring area under the receiver-operating-characteristic curve (AUROC) and decision curve analysis. RESULTS: A total of 304 patients met the inclusion criteria, with a median (interquartile range) age of diuretic renogram at 4 (2-7) months. Of all patients, 48 (16%) were low risk, 102 (33%) were intermediate risk, 156 (51%) were high risk of obstruction based on diuretic renogram. The AERO achieved a binary AUROC of 0.84, multi-class AUROC of 0.74 that was superior to the SFU grade, and external validation (n = 64) binary AUROC of 0.76. The most important features for prediction included age, anteroposterior diameter, and SFU grade. We deployed our application in an easy-to-use application (https://sickkidsurology.shinyapps.io/AERO/). At a threshold probability of 30%, the AERO would allow 66 more patients per 1000 to safely avoid a renogram without missing significant obstruction compared to a strategy in which a renogram is routinely performed for SFU Grade ≥3. CONCLUSIONS: Coupled with machine learning, routine US findings can improve the criteria to determine in which children with isolated hydronephrosis a diuretic renogram can be safely avoided. Further optimisation and validation are required prior to implementation into clinical practice.

Determination of tissue tracer transit of Technetium-99m-mercaptoacetyltriglycine diuretic renography in infants with suspected ureteropelvic junction obstruction - A multicenter prospective observational study.

INTRODUCTION: There is an ongoing controversy regarding management of ureteropelvic junction obstruction in infants, with a shift towards a non-operative approach. However, precise predictors of outcome are lacking. Recent studies postulated a high prognostic value of Technetium-99m-mercaptoacetyltriglycine tissue tracer transit with regard to the development of an impaired differential renal function and its potential improvement following pyeloplasty. OBJECTIVE: To evaluate the prognostic value of Technetium-99m-mercaptoacetyltriglycine tissue tracer transit for the occurrence of changes in differential renal function in infants with suspected unilateral ureteropelvic junction obstruction in a prospective observational multicenter study. STUDY DESIGN: Infants below 3 months of age with a unilateral isolated hydronephrosis ≥ grade 3 received ultrasound and Technetium-99m-mercaptoacetyltriglycine diuretic renography at two different time points (timepoint 1 and timepoint 2). Data were analyzed at local centers and at the study center and were collected in an internet-based database system. Tissue tracer transit was determined for each diuretic renography, inter-observer variation for tissue tracer transit and standard parameters for judgement of differential renal function development were assessed. RESULTS: Thirty-seven patients were analyzed. Median age was 11 weeks (7-15) at timepoint 1 and 26 weeks (19-33) at timepoint 2. A delayed tissue tracer transit at timepoint 1 was not associated with deterioration of differential renal function at timepoint 2 in both, locally (10/37 cases) and centrally (4/37) analyzed cases. However, sensitivity and specificity were poor. The intraclass correlation coefficient comparing local and central findings of tissue tracer transit and renal drainage demonstrated poor or fair agreement. Analysis of standard parameters for differential renal function development revealed a prognostic value only for the dichotomized anteroposterior renal pelvic diameter (APD, p = 0.03, 95%-CI 1.2-22.2). DISCUSSION: Regarding the primary endpoint of our study, we could not confirm the hypothesis that delayed tissue tracer transit reliably predicts a subsequent decline in differential renal function in the cohort of patients studied. Whether the low age of the patients, technical problems in the correct assessment of tissue tracer transit by the investigator in early infancy, the study design, or the parameter itself played a role is debated. CONCLUSION: In the presented setting tissue tracer transit was not useful as a predictive parameter for deterioration of differential renal function in infants with suspected unilateral ureteropelvic junction obstruction. Sensitivity and specificity of tissue tracer transit were not sufficient for risk stratification. Improved utility of tissue tracer transit as a marker might be achieved using a different study setting.

Computer assisted interpretation of Tc-99m mercaptoacetyltriglycine diuretic scintigraphy enhances resident performance.

OBJECTIVE: iRENEX is a software module that incorporates scintigraphic and clinical data to interpret 99m Tc- mercaptoacetyltriglycine (MAG3) diuretic studies and provide reasons for their conclusions. Our objectives were to compare iRENEX interpretations with those of expert physicians, use iRENEX to evaluate resident performance and determine if iRENEX could improve the diagnostic accuracy of experienced residents. METHODS: Baseline and furosemide 99m Tc-MAG3 acquisitions of 50 patients with suspected obstruction (mean age ± SD, 58.7 ±â€…15.8 years, 60% female) were randomly selected from an archived database and independently interpreted by iRENEX, three expert readers and four nuclear medicine residents with one full year of residency. All raters had access to scintigraphic data and a text file containing clinical information and scored each kidney on a scale from +1.0 to -1.0. Scores ≥0.20 represented obstruction with higher scores indicating greater confidence. Scores +0.19 to -0.19 were indeterminate; scores ≤-0.20 indicated no obstruction. Several months later, residents reinterpreted the studies with access to iRENEX. Receiver operating characteristic (ROC) analysis and concordance correlation coefficient (CCC) quantified agreement. RESULTS: The CCC among experts was higher than that among residents, 0.84, versus 0.39, respectively, P  < 0.001. When residents reinterpreted the studies with iRENEX, their CCC improved from 0.39 to 0.73, P  < 0.001. ROC analysis showed significant improvement in the ability of residents to distinguish between obstructed and non-obstructed kidneys using iRENEX ( P  = 0.036). CONCLUSION: iRENEX interpretations were comparable to those of experts. iRENEX reduced interobserver variability among experienced residents and led to better agreement between resident and expert interpretations.

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.

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.

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.

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.

Evaluation of N-(6-[18F]Fluoropyridin-3-yl)glycine PET renography to detect renal function progression in a rat model of diabetic nephropathy.

OBJECTIVE: Given the limitation of biomarkers to predict the renal function progression in diabetic nephropathy, N-(6-[18F]Fluoropyridin-3-yl)glycine (6-[18F]FPyGly) was used to evaluate renal function progression in a rat model of diabetic nephropathy. METHODS: Twenty male Sprague-Dawley rats were randomly divided into four groups, including the healthy control group (HC group), diabetic nephropathy group (DNM group), routine diet treated diabetic nephropathy group (RDNM group), and high fat/high sucrose -diet-fed diabetic nephropathy group (HDNM group). All renal function parameters were determined from animal PET renograms. P and Tmax represent the curve peak counts and the time to the curve peak counts of 6-[18F]FPyGly in kidneys after injection, C1/2 and the 15 min/Peak ratio represent the time from peak to 1/2 peak in the clearance phase, and the ratio of the curve counts at 15 min to the curve peak counts. RESULTS: P, Tmax, C1/2, and 15 min/peak ratio of each rat were significantly correlated with S-Cr, BUN. There were significant differences in Tmax, P, serum creatinine (SCr), and blood urea nitrogen (BUN) levels between HC and DNM groups. P and the 15 min/Peak ratio were significantly different among DNM, RDNM, and HDNM groups, while Tmax and C1/2 were only significantly different between DNM and RDNM or HDNM groups. There only was a significant difference in BUN between the DNM and HDNM groups. CONCLUSION: The renal function parameters P, Tmax, C1/2 and 15 min/peak value obtained by dynamic renal imaging based on 6-[18F]FPyGly could reflect changes of renal function in rats, which had a good correlation with SCr and BUN, and showed more efficient in the diagnosis of diabetic nephropathy and renal function classification than SCr and BUN.