The Importance of Obtaining Conjugate Views on Renographic Evaluation of Large Hydronephrotic Kidneys: An In Vitro and Ex Vivo Analysis

Determining Split Renal Function in Children With Ureteropelvic Junction Stenosis: Technetium-99m Mercaptoacetyltriglycine (Tc-99m MAG-3) or Technetium-99m Dimercaptosuccinic Acid (Tc-99m DMSA)?

Background Ureteropelvic junction stenosis (UPJS) is the most common cause of clinically significant antenatal hydronephrosis. We compared separate renal function results obtained using technetium-99m-mercaptoacetyltriglycine (Tc-99m MAG-3) and technetium-99m-dimercaptosuccinic acid (Tc-99m DMSA) in pediatric patients with UPJS to evaluate the adequacy of Tc-99m MAG-3 scintigraphy and the necessity of additional Tc-99m DMSA scintigraphy during follow-up. Methodology Patients diagnosed with hydronephrosis in the Pediatric Nephrology Department of Pamukkale University Faculty of Medicine over a period of 10 years (2012-2022) were evaluated retrospectively. Patients who had been diagnosed with UPJS and underwent both Tc-99m MAG-3 and Tc-99m DMSA scintigraphy during follow-up were included in the study. Technetium-99m-labeled MAG-3 and DMSA scans were re-evaluated for all patients by the Department of Nuclear Medicine. Results The study included 52 children with unilateral UPJS (12 girls and 40 boys) with a mean age of 6.34 ± 4.81 years (range: 2.97-9.79 years). Thirty-six patients (69.2%) were diagnosed antenatally. Differential renal function in Tc-99m DMSA was 46.94 ± 10.64 and in Tc-99m MAG-3 was 43.08 ± 11.18; the functions were lower in Tc-99m MAG-3, but the values were within normal limits for both groups (p=0.0001, z=-3.893). When differential renal functions were compared between Tc-99m DMSA and Tc-99m MAG-3 results, a statistically significant positive and strong correlation was found in the kidney with ureteropelvic junction obstruction (UPJO) (p=0.0001, r=0.752). When classifying the Tc-99m MAG-3 and Tc-99m DMSA results in the kidney with UPJO (supranormal, normal, low function) for the determination of differential renal functions, there was a consistency of 76%, and it was correlated (p=0.0001, k=0.456). While two patients had supranormal function and 13 patients had low function in Tc-99m MAG-3, five patients had supranormal function, and eight patients had low function in Tc-99m DMSA. Conclusions Some studies in the literature have reported that Tc-99m MAG-3 causes supranormal function measurements in patients with UPJS; our results showed that Tc-99m DMSA resulted in a higher rate of supranormal values for affected kidneys. We believe that Tc-99m DMSA should not be performed in addition to Tc-99m MAG-3 scintigraphy in the follow-up of every patient with UPJS but can be utilized in select cases, such as patients with surgical indications and those suspected before surgery.

Ureteropelvic junction obstruction with polyps in children: clinical manifestations and supranormal preoperative differential renal function

OBJECTIVE

To describe and analyze the clinical manifestation and pre-DRF of UPJO children with polyps and explore the possible influencing factors of supranormal pre-DRF.

PATIENTS AND METHODS

All patients undergoing primary Anderson-Hynes pyeloplasty for UPJO due to polyp were retrospectively reviewed. Patients' characteristics, parameters of ultrasound and dynamic renograms (DR) were recorded in elaborate. Pre-DRF in groups of different age, weight, gender, pain, grade of hydronephrosis, anterio-posterior pelvic diameter (APD), length of kidney and postoperative ultrasonic parameters were compared.

RESULTS

A total of 18 UPJO children with polyps were included. Five (27.78%) patients had SFU III grade of hydronephrosis. Seven (38.89%) patients were supranormal pre-DRF. All patients had pre-DRF > 40%. Drainage curve was delayed excretion in 12 (66.67%) patients and T1/2 < 20 min was in 4 (22.22%) patients. Among the 16 patients who underwent preoperative IVP examination, 15 (93.75%) patients had concentration of intrarenal pelvis contrast agent within 10 min. No significant difference in post-APD reduction rate and post-minPT increased was found between supranormal pre-DRF and non-supranormal pre-DRF groups. The supranormal pre-DRF was more likely to occur in young and low-weight children.

CONCLUSION

The preoperative renal function of UPJO patients with polyps was well preserved, and 38.89% of them had supranormal pre-DRF. Patients with supranormal pre-DRF can be managed with the same strategies as those with normal renal function.

Supranormal differential renal function on MAG3 scan in children with ureteropelvic junction obstruction - Prevalence and pyeloplasty during follow-up

BACKGROUND

Children with suspected ureteropelvic junction obstruction (UPJO) may present with a paradoxical ipsilateral supranormal differential renal function (snDRF) on 99mTechnetium mercaptoacetyltriglycine scintigraphy (MAG3 scan).

OBJECTIVE

The aim was to investigate the prevalence of snDRF, the risk of pyeloplasty among children with UPJO and snDRF, and to explore the experience of snDRF among international pediatric urologists.

METHODS

A retrospective cohort study of children with suspected unilateral UPJO who underwent MAG3 scan at four hospitals in Sweden between 2005 and 2020. SnDRF was defined as DRF ≥55%. Normal DRF was defined as DRF 45-54%. Primary outcome was risk of pyeloplasty. Indications for pyeloplasty were loss of >10%-points of differential renal function (DRF), ipsilateral DRF <40%, or symptomatic UPJO. Logistic and cox regressions were performed in univariate and multivariable analyses, adjusting for age, gender, year, laterality, antenatal hydronephrosis, anterior-posterior diameter (APD), and kidney size. An international questionnaire regarding the management of snDRF was developed and distributed to pediatric urologists.

RESULTS

The prevalence of snDRF was 19%. SnDRF was more common in boys, children with antenatal hydronephrosis, children undergoing their first MAG3 scan at a younger age, and in the left kidney. After further exclusion of 70 children with DRF <45%, a total of 264 were included for longitudinal follow-up of median 6.6 (IQR 2.5-11.5) years. SnDRF was not associated with increased risk of pyeloplasty (adjusted OR 0.98 (95% CI 0.41-2.33), p = 0.96, and adjusted HR 1.00 (95% CI 0.53-1.91), p = 0.99) or time to pyeloplasty (1.1 years vs. 1.6 years, p = 0.40). Among the 79 surveyed pediatric urologists, a majority would not change clinical UPJO-management based on the presence or absence of ipsilateral snDRF.

DISCUSSION

There are only a few studies considering the need of pyeloplasty based on the presence of snDRF and this is the first survey among pediatric urologists on its management. With more included patients than previous studies, this study showed a snDRF prevalence of 19%, congruent with the findings of others. The underlying cause of snDRF is debated, but it cannot solely be explained as an artifact of hydronephrotic kidneys. Further studies on the clinical implications of snDRF are warranted, since DRF influences the decision to operate.

CONCLUSION

A fifth of all children with suspected UPJO presented with ipsilateral snDRF on initial MAG3 scan, and snDRF was not associated with a greater risk of pyeloplasty. Supported by a large group of international pediatric urology colleagues, this study concludes that the same clinical follow-up and management apply, regardless of presence of snDRF.

Association of the Hydronephrosis Severity Score With Likelihood of Pyeloplasty: A Large Prospective Database Analysis

OBJECTIVE

To apply and reproduce this scoring system in our prenatal hydronephrosis population with ureteropelvic junction obstruction (UPJO)-like hydronephrosis (HN), specifically looking at determining better HHS cutoffs that would allow for stratification into three risk categories: spontaneous HN resolution, observation, and surgery.

METHODS

A prospectively collected prenatal hydronephrosis database was reviewed to extract UPJO-like HN patients. Children with vesicoureteral reflux, primary megaureter, bilateral HN, and other associated anomalies were excluded. Only patients who had an ultrasound and mercaptoacetyltriglycine renal scan at a minimum of 2-time points were included. Hydronephrosis Severity Score was calculated at the initial, interim, and last follow-up clinic visits. Scores were analyzed regarding its usefulness to determine which patients would have been more likely to undergo pyeloplasty.

RESULTS

Of 167 patients, 131 (78%) were male, 119 (71%) had left UPJO-like, and 113 (67%) had a pyeloplasty. The median age at baseline was 2months (interquartile range 1-4). According to initial (first clinic visit) Hydronephrosis Severity Score, 5/36 (14%) patients with a 0-4 score, 93/116 (80%) with a 5-8 score, and 15/15 (100%) with a 9-12 score underwent pyeloplasty, respectively (P < .01).

CONCLUSION

The proposed HHS system for UPJO-like HN patients is reproducible, however, cut-off values need to be reassessed to accurately reflect true risk categories, as the purpose of this system is to differentiate those who have HN severe enough to require intervention from those who can be managed nonsurgically. Changing risk groups to mild (0-3), moderate (4-6), and severe (7-12) allowed for better discrimination between patients who underwent surgical intervention from those who did not in our dataset.

The sequence of intervention determines the risk of early postoperative acute kidney injury in infants with bilateral ureteropelvic junction obstruction

INTRODUCTION AND OBJECTIVES

The management of bilateral ureteropelvic junction obstruction (UPJO) is greatly debated. We aim to identify the risk of early postoperative acute kidney injury (AKI) in relation to the sequence of intervention in children with bilateral UPJO managed in a sequential manner.

METHODS

A single center database was retrospectively reviewed for children ≤2 years who underwent bilateral pyeloplasty. According to the differential renal function on the preoperative renograms, patients were categorized into group A: pyeloplasty on the poorer functioning kidney first and group B: pyeloplasty on the better functioning side first. Serum creatinine and eGFR, using the modified Schwartz formula, were evaluated at four time points (I): before the first intervention (II): within 48 h of the first intervention (III): before the second intervention and (IV): within 48 h of the second intervention. Preoperative and postoperative values were compared. The incidence of early postoperative AKI in both groups was defined according to the Acute Kidney Injury Network (AKIN) criteria.

RESULTS

The study comprised 46 children treated by staged pyeloplasty, 28 of them underwent pyeloplasty on the poorer functioning side first. Baseline serum creatinine and eGFR were not significantly different between both groups. Patients who underwent pyeloplasty on the poorer functioning side first, had a significant decline of eGFR after the first intervention (p = 0.006). Conversely, no significant eGFR changes were observed after the first or second interventions in the other group (figure). Overall, 64.3% and 33.3% of patients developed some degrees of AKI when intervention was started on the poorer and better functioning renal units, respectively (p = 0.04).

DISCUSSION

Bilaterality is seen in approximately ¼ of patients with UPJO. Oftentimes, both renal units are asymmetrically affected with little data to guide surgeons on the optimal sequence of intervention. Following pyeloplasty, 52.2% of the evaluated children with bilateral UPJO had early postoperative AKI, mostly of low stage. Our data suggest that intervening first on the better functioning side allows for better recovery of the renal functional reserve and lowers the risk of postoperative AKI.

CONCLUSION

In children with bilateral UPJO, starting intervention on the poorer functioning kidney is associated with increased risk of postoperative AKI. Long-term prospective studies are needed to confirm our findings.

Functional recoverability post-pyeloplasty in children with ureteropelvic junction obstruction and poorly functioning kidneys: Systematic review

BACKGROUND

The management of poorly functioning kidneys (PFK) associated with ureteropelvic junction obstruction (UPJO) is controversial. There is contradictory information about how to best manage these cases: pyeloplasty or nephrectomy?

OBJECTIVE

To systematically summarize the available evidence concerning the effects of pyeloplasty on the differential renal function of PFK in children with unilateral UPJO, highlighting the ongoing challenges in their definition, management, and long-term follow-up. In addition, we aim to verify potential predictors of renal functional recoverability that could help clinicians choose candidates for pyeloplasty.

METHODS

We searched several databases including PubMed, Embase, and Cochrane Library CENTRAL until August 20, 2021, according to the PRISMA guidelines. The following concepts were searched: pediatric, ureteropelvic junction obstruction, UPJO, pyeloplasty, recovery, split renal function, and differential renal function. We enrolled studies where the PFK was defined as preoperative differential renal function (DRF) ≤30% by renal scintigraphy. Potential predictors of renal functional recoverability were assessed and compared among studies. The quality of the included studies was evaluated using a modified version of the Newcastle-Ottawa scale (NOS).

RESULTS

1499 citations perceived as relevant to screening were retrieved. After screening, 20 studies were included, comprising a total of 625 cases. The number of patients in each study varied between 5 and 84, while the average post-surgical follow-up duration ranged between 3 months and 180 months. The most significant preoperative predictive factor for postoperative functional recoverability was the baseline DRF, especially when antenatally diagnosed. The quality was considered average in a significant portion of included studies.

CONCLUSION

A significant proportion of PFK showed an increase of DRF post-pyeloplasty. However, no consistent predictive factors for functional recoverability have yet been determined apart from preoperative DRF. Until further evidence appears, pyeloplasty should be considered a valid option in the armamentarium of UPJO management in PFK.

Factors predicting improvement of differential renal function after pyeloplasty in children of ureteropelvic junction obstruction

INTRODUCTION

To evaluate differential renal function (DRF) in unilateral ureteropelvic junction obstruction (UPJO) patients under 18 years old after pyeloplasty and to identify factors predicting postoperative improvement.

MATERIAL AND METHODS

A total of 95 patients with unilateral UPJO treated by pyeloplasty between March 2019 to March 2020 were prospective enrolled. All patients had preoperative dynamic renal scintigraphy and were required to review after surgery 6 months. We defined DRF improvement as postoperative DRF increased ≥5% (If preoperative DRF less than 55%) or postoperative DRF reduced ≥5% and reached a normal range (45-55%) (preoperative DRF more than 55%) with drainage improvement. Drainage improvement indications were defined as a resolution of symptoms; decrease in hydronephrosis without requiring additional procedures and T_1/2＜20min in dynamic renal scintigraphy. All parameters were statistically compared.

RESULTS

In the study, 28 (29.5%) patients showed improvement in postoperative DRF, and 67 (70.5%) patients maintained stable postoperative DRF. Gender, age, baseline DRF, anteroposterior pelvic diameters (APD), minimum and maximum renal parenchymal thickness (PT), and anterior-posterior diameter/maximum renal parenchymal thickness (APD/PT) were correlated with postoperative DRF improvement in univariable analysis. In the multivariable analyses, maximum PT and APD/PT were predictors of improvement in postoperative DRF.

DISCUSSION

In our study, the maximum PT was associated with the improvement of renal function in patients with UPJO, and when the thickest part of the renal parenchyma was measured, APD/PT can predict the improvement of renal function. We infer that the compression of the thickest part of the renal parenchyma may be the reason for the impaired renal function in some patients, and when the obstruction was relieved, the compressed parenchyma function can be significantly improved.

CONCLUSIONS

Postoperative DRF of UPJO patients can be effectively improved and preserved through pyeloplasty. Maximum PT and APD/PT can predict improvement of renal function in patients with UPJO after pyeloplasty.

Urinary biomarkers can identify the need for pyeloplasty in presence of supranormal differential renal function in antenatally diagnosed unilateral hydronephrosis

INTRODUCTION

Decision for surgery can be challenging in children with AH (Antenatal Hydronephrosis) especially in the setting of supranormal differential renal function (SnDRF).

OBJECTIVE

Aim of this study is to investigate whether IP-10 (interferon gamma-induced protein 10), MCP-1 (monocyte chemotactic protein-1), NGAL (neutrophil gelatinase-associated lipocalin), CA 19-9 (carbohydrate antigen 19-9), and KIM-1 (kidney injury molecule-1) can identify the need for pyeloplasty in presence of SnDRF in antenatally diagnosed unilateral hydronephrosis.

STUDY DESIGN

A prospectively collected urinary biomarker database was used for the study. There was a total of 53 patients in the AH group. Nineteen children with no history of AH and a normal urinary ultrasonography were taken as controls. Patients with initial ipsilateral DRF (Differential Renal Function) over 50% were included in the SnDRF group while the remaining were named as non-SnDRF. Patients that didn't undergo surgery were classified as non-obstructive dilation (NOD) in both groups.

RESULTS

Pyeloplasty was performed in 6/20 patients in SnDRF group, and in 19/33 patients in non-SnDRF group. Biomarker levels in the pyeloplasty and NOD groups were not affected by the presence or absence of SnDRF (p = 1.00, for both). Urinary NGAL, and CA 19-9 could determine the need for surgery in SnDRF group with 83% and 100% sensitivity, 86% and 79% specificity, respectively whereas urinary IP-10 and KIM-1 could with 84% and 83% sensitivity, 57% and 71% specificity, respectively. Urinary MCP-1 could differentiate patients who underwent surgery with 83% sensitivity and 50% specificity in SnDRF groups.

CONCLUSION

Our results showed that biomarker levels were not affected whether the kidney has SnDRF. Furthermore, in patients with SnDRF, NGAL and CA 19-9 appear to better estimate requirement for surgical correction before deterioration of renal function.

Supranormal differential renal function in adults with ureteropelvic junction obstruction: Does it really exist?

Introduction

Some patients with ureteropelvic junction obstruction (UPJO) have supranormal differential renal function (snDRF). We aimed to study the outcomes of pyeloplasty in adult patients with UPJO and either snDRF or normal differential renal function (nDRF) and to identify preoperative factors responsible for the snDRF phenomenon.

Materials and Methods

We retrospectively retrieved data for all patients who underwent pyeloplasty and had snDRF (differential renal function [DRF] ≥55%) and nDRF (DRF between 45 and 55%) preoperatively. Preoperative radiological data using computed tomography or magnetic resonance imaging were correlated with the presence of snDRF phenomenon. In addition, scintigraphic findings pre- and post-operatively were also assessed to evaluate the functional outcomes.

Results

Of a total of 856 patients, 31 had snDRF (group 1) and 42 had nDRF (group 2). After a mean of 37 months' follow-up in Group 1, 22 patients developed DRF reduction with non-obstructive pattern. Mean DRF % decreased from 59 ± 2.8 to 48 ± 13 (P < 0.0001). However, in Group 2, five patients had DRF decrease. Four patients developed snDRF phenomenon postoperatively. Increased renal pelvis volume ≥50 mm³ and increased anteroposterior pelvic diameter (APD) ≥37 mm were found to predict snDRF phenomenon. The same findings, in addition to preoperative snDRF, correlated with postoperative DRF decrease.

Conclusion

SnDRF function could be expected in patients with increased renal pelvis volume and APD. The absolute value or changes in DRF are not reliable to judge treatment failure.

Ultrasound-Based Scoring System for Indication of Pyeloplasty in Patients With UPJO-Like Hydronephrosis

Background: Previous scoring systems have used renal scan parameters to assess severity of ureteropelvic junction obstruction-like hydronephrosis (UPJO-like HN), however this information is not always reliable due to protocol variation across centers and renogram limitations. Therefore, we sought to evaluate the Pyeloplasty Prediction Score (PPS), which utilizes only baseline ultrasound measurements to predict the likelihood of pyeloplasty in infants with UPJO-like. Methods: PPS was developed using three ultrasound parameters, Society of Fetal Urology (SFU) grade, transverse anteroposterior (APD), and the absolute percentage difference of ipsilateral and contralateral renal lengths at baseline. PPS was evaluated using prospectively collected prenatal hydronephrosis data (n = 928) of patients with UPJO-HN. Children with vesicoureteral reflux. primary megaureter, other associated anomalies, bilateral HN and <3 months of follow-up were excluded. Scores were analyzed regarding its usefulness in predicting which patients would be more likely to undergo pyeloplasty. Sensitivity, specificity, likelihood ratios (LR) and receiver operating characteristic (ROC) curve were determined. Results: Of 353 patients, 275 (78%) were male, 268 (76%) had left UPJO-like HN, and 81 (23%) had a pyeloplasty. The median age at baseline was 3 months (IQR 1-5). The PPS system was highly accurate in distinguishing patients who underwent pyeloplasty using baseline ultrasound measurements (AUC: 0.902). PPS of 7 and 8 were found to have a sensitivity of 85 and 78%, and specificity of 81 and 90%, respectively. PPS of 8 was associated with a LR of 7.8, indicating that these patients were eight times more likely to undergo pyeloplasty. Conclusion: Overall, PPS could detect patients more likely to undergo pyeloplasty using baseline ultrasound measurements. Those with a PPS of eight or higher were eight times more likely to undergo pyeloplasty.

Comparative Outcome Analysis of Children Who Underwent Pyeloplasty for Ureteropelvic Junction Obstruction Associated With or Without Supranormal Differential Renal Function

OBJECTIVE

To compare pyeloplasty outcomes in children with and without "supra-normal" differential renal function (SNDRF) defined as >55% differential renal function (DRF) in children with ureteropelvic junction obstruction.

METHODS

Our prospectively collected pyeloplasty database (2008-2015) was reviewed (n = 151). A total of 140/151 (93%) patients had preoperative renograms and 26/140 (19%) were found to have SNDRF (DRF ≥ 55%). Of 151 patients, 51 (34%) had pre- and postoperative renograms allowing determination of change ≥5% in function. After excluding 2 patients with solitary kidneys, a total of 49 patients defined the study group.

RESULTS

Of 49 patients, 12 had SNDRF and 37 did not. Baseline characteristics were similar including mean age at surgery (47.3 months vs 45.4 months) and time to surgery (8.7 months vs 9.8 months). Mean preoperative anteroposterior diameter was significantly different between groups (23.2 mm vs 31.0 mm; P = .04), but postoperative was similar (9.0 mm vs 12.1 mm; P = .14). Mean preoperative DRF was 60.2% in the SNDRF group vs 44.3% in the non-SNDRF. Mean postoperative DRF was 52.4% and 45.3%, respectively (P = .04). There were 9/12 (75%) SNDRF patients who experienced ≥5% loss in function compared to 2/37 (5%) in the non-SNDRF group (P < .01).

CONCLUSION

Three-quarters of SNDRF patients demonstrated a decline of ≥5%DRF postoperatively when compared to non-SNDRF. This finding may not reflect true elevated renal function, but rather hyperfiltration in the setting of obstruction, which-if unrecognized as such-could result in postponing an otherwise beneficial surgical intervention.