Interpretation of the renogram: problems and pitfalls in hydronephrosis in children

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.

Can pyeloplasty restore normal renal function in patients with severe unilateral ureteropelvic junction obstruction and DRF < 35

PURPOSE

To assess the outcome of successful pyeloplasty in infants with Ureteropelvic Junction Obstruction (UPJO) and a differential renal function of (DRF) < 35% whether they can attain normal postoperative renal function or not.

METHODS

All children who were diagnosed with antenatal hydronephrosis due to UPJO were presented to our institutions and were prospectively followed up. Pyeloplasty was performed based on predefined indications such as: initial DRF ≤40%, progression of hydronephrosis, and febrile urinary tract infection (UTI). A total of 173 children, who had successful surgical intervention due to impaired DFR, were divided according to their pre-intervention DRF value as follows: DRF <35% (group I) and DRF 35-40% (group II). The renal morphology and function changes were recorded and used for comparison between both groups.

RESULTS

Group I was comprised of 79 patients, and group II included 94 patients. Pyeloplasty achieved significant improvement in the anatomical and functional indices in both groups (p-value <0.001). The degree of improvement in Anteroposterior diameter (APD) and cortical thickness was comparable in both groups (P-value, 0.64 and 0.44 respectively). While the improvement in the DRF was significantly higher in group I (16.06 ± 6.6) than in group II (6.25 ± 2.66) (P-value <0.001). Despite that, a significantly higher percentage of infants in group II (61.7%) achieved normal final DRF compared with only (10.1%) in group I (Figure).

CONCLUSION

Even in severely impaired renal function (<35%), successful pyeloplasty can recover a significant part of lost renal function. However, most of these patients do not achieve normal postoperative renal function.

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.

Normative values for ureteral diameter in children

BACKGROUND

Assessment of the ureter is a fundamental part of the radiologic evaluation of the urinary tract. Abnormal ureteral dilation warrants further investigation to assess the etiology, which includes obstruction and/or reflux. Despite this fundamental need, there are no established normative values in children based on imaging.

OBJECTIVE

To provide normative values for ureteral diameter in pediatric patients with age-related ranges.

MATERIALS AND METHODS

We retrospectively reviewed all magnetic resonance (MR) urography studies and chose only normal ureters for assessment. The images were analyzed on commercially available software to assess maximum internal diameter. Manual measurements were done in cases where the images were below the resolution for automated assessment. Maximum intraluminal ureteral diameters were measured in upper, mid and lower thirds and the average of the three maximum ureteral diameters was used to obtain the average widest internal ureteral diameter. Multivariable linear regression was performed to test the association between the calculated diameter and gender. Differences in sizes between the left and right ureter were assessed using paired Wilcoxon signed rank test.

RESULTS

One hundred twenty-one MR urography studies were selected, which included 160 ureter units. The diameter increases progressively with age, ranging from 3.2 mm during infancy to 5.0 mm in patients older than 16 years of age. After 9 years of age, the average widest internal ureteral diameter is slightly larger in males compared to females (odds ratio [OR]=1.91, 95% confidence interval [CI] [1.63, 2.25], P<0.0001). The right ureter was slightly larger than the left (3.9 mm vs. 3.7 mm, P=0.004) among 39 patients in whom both right and left ureter units were included. The average mid ureteral diameter is widest, followed by the distal third then proximal third.

CONCLUSION

We present the normative values for the average widest internal ureteral diameter based on laterality and different segments. In the pediatric population, 3.8 mm should be considered the average widest internal ureteral diameter.

Diuretic Renal Scintigraphy Protocol Considerations

Diuretic renal scintigraphy plays a critical diagnostic role by providing a physiologic means for differentiating between obstructive and nonobstructive hydronephrosis as well as assessing the function of the affected kidney. The exam accuracy is highly dependent upon and benefits from close attention to the protocol. This article reviews kidney anatomy and physiology, patient preparation, available radiopharmaceuticals, diuretic administration, acquisition, processing, quantification, and interpretation criteria.

Quantitative assessment of renal perfusion in children with UPJO by contrast enhanced ultrasound: A pilot study

BACKGROUND

Contrast-enhanced ultrasound (CEUS) is a new potential modality for the quantitative evaluation of the microvascular perfusion of a parenchymal organ.

OBJECTIVE

To prospectively and quantitatively analyse the role of CEUS in evaluating renal perfusion for assessing renal function in children with ureteropelvic junction obstruction (UPJO).

METHODS

The study protocol was approved by the local ethics committee, and written informed consent was obtained from the patients' parents or guardians. Ultrasonography, CEUS, and radioisotope renography were performed for 51 children (42 boys, 9 girls; mean age, 6.75 ± 4.14 years) with unilateral UPJO. The slope of the ascending curve (A), time to peak (TTP), peak intensity (PI), and area under the curve (AUC) were recorded during CEUS; quantitative data were calculated by QLab system (semiautomated border tracking, Philips Healthcare) software. Sensitivity and specificity values were determined for CEUS with respect to radioisotope renography.

RESULTS

CEUS was used to evaluate 102 kidneys in 51 patients, for which the perfusion time-intensity curve (TIC) was determined. The TIC of renal cortical perfusion in all groups showed an asymmetrical single-peak curve, which could be clearly distinguished between the experimental group and the control group. Compared with the control group, the experimental group showed a markedly prolonged TTP but a significantly decreased A (P < 0.05). There was no significant correlation between the AUC, PI and differential renal function (DRF), but the correlation coefficient between TTP, A and DRF remained significant (p < 0.001).The receiver operating characteristic (ROC) curves drawn to differentiate DRF using the TTP value yielded an area under the ROC curve (AUROC) of 0.86. For a quantitative assessment of DRF less than 40% by CEUS, the sensitivity and specificity values were 92.86% and 76.14%, respectively.

DISCUSSION

Unlike in previous studies, no significant difference in the AUC or PI was found between the control group and the experimental group in this study (P > 0.05). Renal blood perfusion could not be evaluated overall by CEUS. Parenchymal thinning may be considered a limitation to CEUS.

CONCLUSIONS

This preliminary experience represents the first report of evaluating the diagnostic value of CEUS in assessing renal function in children with UPJO. CEUS is a highly sensitive, rapid, and cost-effective diagnostic imaging modality for detecting and monitoring renal function noninvasively.

Renogram image characteristics and the reproducibility of differential renal function measurement

PURPOSE

Patient factors such as age and glomerular filtration rate (GFR), have been implicated as causes for poor reproducibility of differential renal function (DRF) estimates on 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) renography. This study aims to investigate factors associated with the reproducibility of DRF measurements.

METHODS

The association between age, GFR and imaged derived image characteristics and reproducibility of repeated DRF estimates calculated using the area under the curve method and the Rutland Patlak method was analysed for cohort 1 (n = 127). The association between these variables and reproducibility of DRF was tested with univariate linear regression. The univariate linear regression results were used to plan the multiple linear regression combinations.The associations between variables identified and reproducibility of DRF values were then tested in a second cohort (n = 227).

RESULTS

The R2 values for goodness-to-fit for the multiple regression models ranged from 0.33 to 0.49 for cohort 1 and from 0.17 to 0.22 for cohort 2. Left kidney to background ratio (LKTBR) was significant in all the multiple linear regression combinations (P < 0.05). Right kidney to background ratio (RKTBR), right renal margins well defined, right renal margins poorly visualised, time visualisation right calyces and age were significant in most combinations. The reproducibility of DRF measurement was decreased when the kidney to background ratio (KTBR) was ≤2.

CONCLUSION

Only LKTBR, RKTBR, right renal margins well defined, time visualisation right calyces and age predicted reproducibility for the measurement of DRF on 99mTc-MAG3 renograms. The KTBR should be incorporated into the renal processing software as a quality control step. The DRF values should be interpreted with caution if the KTBR is ≤2.0.

Advantages of gravity-assisted diuretic renogram: F + 10 (seated position) method

INTRODUCTION

In 1978, O'Reilly introduced the diuretic renogram using the F + 20 method. Initially, the patient was examined in the seated position. A dose of 40 mg furosemide was injected intravenously 20 min following tracer injection and dynamic acquisition was prolonged for 15-20 min. In 1992, the guidelines suggested to study patients in the supine position to avoid risk of diuretic-induced hypotension and reduce patient movement. Unfortunately, equivocal findings were reported in 15-30% of cases. Side effects such as bladder fullness and disruption because of voiding were reported. Several methods had been proposed in the supine position, such as the well-tempered diuretic renogram F + 20, F - 15, F0 and F + 2, with different time in minute of diuretic administration in relation to tracer injection. However, as confirmed by many studies, there was no clear evidence suggesting superiority among these methods. We suggest using the diuretic renogram with the F ± 10(sp) method for the diagnosis of obstruction in adult patients with hydronephrosis and for the follow-up in patients who underwent a surgical treatment of the urinary tract.

METHODS

We searched all international guidelines and articles of most influential authors published from 1978 to October 2020 on diuretic renogram.

RESULTS

We selected 60 articles.

DISCUSSION

F + 10(sp) method improves patient compliance avoiding bladder fullness-related problems, without need of catheterization. It allows for a more reliable quantification of the renal output, thanks to outflow indices that are favored by gravity effects.

Renal cortical transit time in the evaluation of prenatally detected presumed pelvi ureteric junction like obstruction: A systematic review

Introduction

Differentiating nonobstructive from obstructive dilatation of the kidney is a clinical dilemma in prenatally detected hydronephrosis. Many radionuclide renogram parameters have been used to differentiate obstructed from non-obstructed units, including cortical transit time (CTT). We evaluate the role of CTT in identifying obstruction through a systematic review.

Methods

A literature search of the MEDLINE, MEDLINE In-Process, and MEDLINE Epub Ahead of Print, EMBASE, Google scholar, Pub Med, and Cochrane Library was done using key words - radionuclide renogram, CTT, parenchymal transit time, cortical transit, renography to identify articles on the subject. The identified articles were assessed for appropriateness and reviewed.

Results

The initial search yielded a total of 1583 articles, after adding the articles from references and applying the inclusion and exclusion criteria a total of 28 articles were selected. CTT showed good inter observer agreement in identifying obstruction. The use of CTT as a single parameter for determining the need for surgery and to identify those kidneys which will have functional improvement after surgery has been evaluated and has been found to be useful. CTT is best used in conjunction with ultrasonography to make clinical decisions.

Conclusion

The commonly used visual method of estimating the CTT, is a promising parameter for the evaluation of prenatally detected pelviureteric junction obstruction. Further well-designed multicenter prospective studies are needed to establish it as the most specific parameter to differentiate obstructive from nonobstructive dilatation of the pelvicalyceal system.

Comparing predictive values of carbohydrate antigen 19-9, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1 in 161 patients with ureteropelvic junction obstruction

BACKGROUND

To evaluate and compare the efficacy of urinary carbohydrate antigen 19-9 (CA19-9), neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule-1 (KIM-1) biomarkers as predictive factors to determine the surgery requirement in patients with ureteropelvic junction obstruction.

METHODS

We obtained urine samples from 161 patients at diagnosis and evaluated their levels of the three biomarkers. The patients were under observation for 2 years; subsequently, they were divided into two groups based on their requirement of pyeloplasty. We determined the correlation between the urinary concentration of the biomarkers and surgical interventions, as well as the kidney function deterioration and sonography outcomes.

RESULTS

The non-surgery group included 60 male and 22 female patients with mean age of 21 months. The surgery group comprised 58 boys and 21 girls with mean age of 26.9 months with no significant difference of age and gender between the two groups. The outcomes were indicative of higher efficacy of CA19-9 level with a sensitivity and specificity of 84.2% and 73.2% at the cutoff point of 59.09 U/ml. Also, a significant negative correlation was detected between the kidney function and the concentrations of CA19-9 and NGAL.

CONCLUSIONS

Our evaluations demonstrate the higher efficacy of CA19-9 to predict the requirement of surgical intervention in comparison with the other biomarkers, as well as a significant correlation between kidney function deterioration and urinary CA19-9 and NGAL. The outcomes of this investigation could pave the way for more extensive clinical application of these urinary biomarkers, besides future research determining the association between markers and kidney fibrosis.

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

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

Assessing alignment between functional markers and ordinal outcomes based on broad sense agreement

Functional markers and their quantitative features (eg, maximum value, time to maximum, area under the curve [AUC], etc) are increasingly being used in clinical studies to diagnose diseases. It is thus of interest to assess the diagnostic utility of functional markers by assessing alignment between their quantitative features and an ordinal gold standard test that reflects the severity of disease. The concept of broad sense agreement (BSA) has recently been introduced for studying the relationship between continuous and ordinal measurements, and provides a promising tool to address such a question. Our strategy is to adopt a general class of summary functionals (SFs), each of which flexibly captures a different quantitative feature of a functional marker, and study its alignment according to an ordinal outcome via BSA. We further illustrate the proposed framework using three special classes of SFs (AUC-type, magnitude-specific, and time-specific) that are widely used in clinical settings. The proposed BSA estimator is proven to be consistent and asymptotically normal given a consistent estimator for the SF. We further provide an inferential framework for comparing a pair of candidate SFs in terms of their importance on the ordinal outcome. Our simulation results demonstrate satisfactory finite-sample performance of the proposed framework. We demonstrate the application of our methods using a renal study.

99mTc-DTPA Diuretic Renography with 3 hours late output fraction in the evaluation of hydronephrosis in children

Objective:

Dynamic renal scintigraphy complemented by late gravity assisted postvoid images to 60 minutes is a frequently used diagnostic test in the evaluation of hydrone- phrosis. The objective of this study is to evaluate the effectiveness in acquiring images at 180 minutes to calculate the late output fraction (LOF) of ^99mTc-DTPA in the diagno- sis of ureteropelvic junction obstruction (UPJO).

Materials and Methods:

A retrospective study of 177 patients (196 renal units) of sus- pected cases of clinical UPJO was conducted. The patients were submitted to at least two dynamic renal scintigraphies of ^99mTc-DTPA, with the addition of furosemide (F0), with a mean age of 4.3±3.8 years for the first study, and a follow-up of 2.7±2.5 years.

Results:

For diagnosis based on renal curves, a 100% sensitivity, 82.2% specificity, positive predictive value (PPV) of 10.4% and negative predictive value (NPV) of 100% were estimated. For diagnosis based on LOF, a 100% sensitivity, 96.3% specificity, PPV of 35.7% and NPV of 100% were estimated.

Conclusion:

A LOF <10% is indicative of UPJO, and a LOF ≥15% is indicative of no UPJO. The data demonstrate that LOF presents equivalent sensitivity and NPV, and higher specificity and PPV in comparison to diagnosis based on renal curves, and is useful in the evaluation and follow-up of suspected cases of UPJO.

Diuretic renography in hydronephrosis: a retrospective single-center study

PURPOSE

Ureteropelvic junction obstruction (UPJO) is one of the most common causes of hydronephrosis other than transient hydronephrosis. In children with unilateral hydronephrosis, mercaptoacetyltriglycine-3 diuretic renography (MAG₃) is used to calculate differential renal function and to assess drainage. The aim of our study is to examine whether anteroposterior pelvic diameter on renal ultrasound (US) scan can predict both differential renal function (DFR) and obstruction in pediatric patients, and whether an US adequately identifies those patients who need further investigation. We also aimed to design a study with a larger sample size than previous studies investigating the relationship between MAG₃ and US.

METHODS

We retrospectively reviewed the MAG₃, US, dimercaptosuccinic acid scan (DMSA) findings, and medical records of pediatric patients with hydronephrosis and/or atrophy who were at follow-up between January 2013 and December 2016 in our center which is located in the south-east region of Turkey.

RESULTS

Two hundred and twenty-five pediatric patients (M/F = 156/69) with unilateral hydronephrosis but without VUR were enrolled in this study. The mean age of the children was 45.4 ± 48.3 months (range 2-173 months). Sixty-nine patients had obstructive pattern on ^99mTc-MAG₃. With respect to obstructive pattern, there was a significant difference between the hydronephrosis groups both with 15 and 20 mm border. An APD of greater than 20 mm had 15.8 times (95% CI 5.72-43.69) higher likelihood of having obstruction MAG3 findings. On the other hand, an APD of greater than 15 cm had 9.2 times (95% CI 3.01-28.57) higher likelihood of having obstruction MAG₃ findings. The incidence of urinary tract infections was lower than in the obstructive group than the other groups. The regression analysis showed that an APD of greater than 20 mm was a risk factor for low DRF (OR = 5.208, 95% CI 1.529-17.743, p = 0.008). However, the regression analysis showed that an APD of greater than 15 mm was not a risk factor low DRF.

CONCLUSIONS

The combination of ultrasound and MAG₃ provides the necessary anatomical and functional information to follow the degree of obstruction and to decide between surgical intervention and conservative follow-up. Our study supports a threshold of 20 mm rather than 15 mm for severe obstruction and a low DRF. An APD threshold greater than 15 mm did not have a predictive value in DRF estimation.

Holding Water: Congenital Anomalies of the Kidney and Urinary Tract, CKD, and the Ongoing Role of Excellence in Plumbing

Congenital anomalies of the kidneys and urinary tracts can result in diminished natal kidney function, possibly through common embryologic pathway disruption or as a result of development taking place in the face of disordered 'post-renal' drainage. Impaired conduit and reservoir function present potential for an ongoing assault leading to further deterioration and progression of chronic kidney disease, a risk that extends to adults with these conditions, even after "correction". The drainage and storage aspects of the urinary system that can impact kidney function are reviewed with attention to correctable or manageable problems including: Bladder dysfunction wherein the low pressure storage of urine is compromised requiring the kidney to work against a pressure gradient, the classic post renal failure problem. The kidney in the aftermath of obstruction which may have lost concentrating capacity leading to a tendency to dehydration ('pre-renal' failure) and through polyuria which exacerbates bladder pressure problems. Further there is an added challenge in evaluation for ongoing or reemergent obstruction in a significantly dilated system where the capacious system leads to slow turnover of urine often requiring a ureteral stent or nephrostomy to clearly establish clinical significance of delayed drainage. Stasis where slow urine flow leads to buildup of debris (stone) or potentiates infection. Vessicoureteral reflux which allows for introduction of lower urinary tract bacteria to the kidney and can lead to pyelonephritis. Conditions which combine problems such as posterior urethral valves where the bladder outlet obstruction compromises kidney function potentially impairing concentrating ability, creates bladder compromise often reducing emptying efficiency or elevating bladder storage pressures, as well as dilating the system potentially promoting stasis. Cognizance of the potential for plumbing problems to further kidney deterioration as patients with congenital urinary tract anomalies, even after they have been repaired is incumbent on those caring for these patients as they age. Thoughtful evaluation of those patients in whom kidney compromise maybe aggravated by drainage and storage disorder will optimize native renal function.

Influence of bladder fullness on the detection of urinary tract obstruction by dynamic renal scintigraphy

Objective

To investigate the influence of bladder fullness on the diagnosis of urinary tract obstruction during dynamic renal scintigraphy with a diuretic stimulator.

Materials and methods

We studied 82 kidneys in 82 patients submitted to dynamic renal scintigraphy with a diuretic stimulator. We compared the proportional elimination of the radiopharmaceutical ^99mTc-DTPA from the kidneys before and after bladder emptying in post-diuretic images, classifying each image as representing an obstructed, indeterminate, or unobstructed kidney.

Results

The overall elimination of ^99mTc-DTPA from the kidneys was 10.4% greater after bladder emptying than before. When the analysis was performed with a full bladder, we classified 40 kidneys as obstructed, 16 as indeterminate, and 26 as unobstructed. When the 40 kidneys classified as obstructed were analyzed after voiding, 11 were reclassified as indeterminate and 3 were reclassified as unobstructed. Of the 16 kidneys classified as indeterminate on the full-bladder images, 13 were reclassified as unobstructed after voiding.

Conclusion

In dynamic renal scintigraphy with a diuretic stimulator, it is important to obtain images after voiding, in order to perform a reliable analysis of the proportional excretion of ^99mTc-DTPA from the kidneys, avoiding possible false-positive results for urinary tract obstruction.

Primary non-refluxive megaureter in children: single-center experience and follow-up of 212 patients

PURPOSE

Primary non-refluxing megaureter (pMU) is a multifaceted and challenging congenital pathology of the urinary tract. We report our 23-year experience with this anomaly in terms of presentation, diagnostic work-up and management.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 212 children diagnosed with pMU between 1986 and 2009 at our institution. Mean follow-up was 45.17 (0-192) months.

RESULTS

Of the total, 168 (79 %) children presented with upper urinary tract dilation on perinatal ultrasound screening. In 44 (21 %) patients, the diagnosis was made following diagnostic work-up of a urinary tract infection (UTI, 18 %) or flank pain (3 %). In total, 203 of 254 pMUs (79.9 %) were successfully treated conservatively during the 23-year observation period. Forty-eight children (23 %) underwent ureteric reimplantation. UTIs occurred in 91 of 212 children (43 %). Of these, 41 (45 %) occurred despite antibacterial infection prophylaxis. Within the past three decades, there has been a marked shift from surgical toward conservative therapy at our institution.

CONCLUSION

Neonatal renal ultrasound is the method of choice to timely identify children with pMU and, alongside dynamic renography, to monitor the clinical course. Nowadays, only a minor subset of children with asymptomatic course requires surgical correction. Antibacterial prophylaxis has the potential to reduce the risk of febrile UTIs. Prospective randomized studies are warranted to provide evidence of the beneficial effect of antibacterial prophylaxis.

[Pitfalls for renogram interpretation in pediatric urology]

Renograms are currently used for functional assessment by pediatric urologists. The aim of the present work was to focus on the potential pitfalls concerning renography. Potential confounding factors are described in reference to concrete cases. The main types of pitfalls concern venous or urinary catheters and background area definition. Protocols and renogram interpretation are critiqued in a bibliographic review. We propose a technical update and original data on the potential pitfalls in renography interpretation. Multidisciplinary discussion between nuclear medicine, pediatrics and pediatric surgery departments is required before drawing conclusions.

Therapeutic approach to Candida bezoar in children

INTRODUCTION

Candida bezoar (CB) is a rare finding in neonates and infants with candiduria, presenting as necrotic debris with proliferating mycelia in the collecting system of the kidney. If initial antifungal medical treatment does not result in clearance of candiduria and disappearance of CB on ultrasound in dilated kidneys, invasive interventions like insertion of nephrostomy tubes (NT) or surgical interventions to drain the kidney are sometimes advocated(.). However, NT placement can be a technical challenge, especially in pre- and dysmature neonates, and NT displacement or obstruction by the CB can lead to suboptimal treatment. Identification of those children who will benefit from invasive renal drainage is important.

OBJECTIVE

This study evaluates the management of patients with CB in three tertiary referral hospitals to determine criteria for intervention.

MATERIALS AND METHODS

A retrospective multicenter chart analysis was conducted of children with candiduria and ultrasonographic demonstration of CB (diagnosed between March 1995 and August 2012). The indication for invasive renal drainage (if performed) and subsequent clinical outcome, serum creatinine levels and ultrasound findings were assessed.

RESULTS

A total of 12 children were included, two of which were premature neonates. Eight children had congenital urogenital anomalies. One older child with acute myeloid leukemia had CB during chemotherapy and one ex-premature developed CB following cerebral candidiasis. All children received systemic antifungal medication; in seven children invasive treatment was added. Indications for invasive treatment were clinical deterioration, progressive renal dilation, pyonephrosis, rising creatinine levels and persistence of CB. Two underwent a Y-cutaneous ureterostomy and nephrostomy tubes were inserted in five children. Percutaneous renal drainage by nephrostomy led to complications in 3 of 6 procedures. In all patients, irrespective of therapeutic modality, follow-up ultrasound demonstrated no de novo changes. No additional parenchymal defects or deterioration of split renal function were seen on DMSA or MAG-3 scan.

DISCUSSION

In the literature renal drainage is suggested in case of complete obstruction. However dilatation is a frequent finding in children as part of the congenital renal anomaly and does not necessarily mean that there is obstruction of the urinary tract. Even in children without candida infections the diagnosis of obstruction is not straightforward, while the results of a MAG 3 scan can be obscured by compromised kidney function, parenchymal bacterial infiltration and neonatal immaturity of the kidney. If candiduria and CB persist despite intensive medical treatment, intensive consultation is required before renal drainage, because NT insertion might be a surgical challenge. Complications such as displacement of the NT, urinoma development, or NT obstruction can occur and was seen in three of six procedures. Premature neonates seem to be more prone to complications due to their small anatomical proportions, requiring medical equipment with small diameters prone to displacement and obstruction. Some studies describe successful pharmaceutical management in the majority of patients with CB. Other studies describe unilateral surgical intervention in children with bilateral CB where unilateral drainage did not influence overall renal outcome. This is in line with our results. A limitation of the present study is its retrospective design. In this population, the motivation for invasive renal drainage or conservative management was not well documented in all cases, and was mainly based on clinical and diagnostic parameters like creatinine levels and radiographic findings.

CONCLUSION

Renal drainage should be considered in selected cases after failure of systemic antifungal treatment. Inserting and maintaining a nephrostomy tube in young children is associated with a high rate of complications; conservative treatment is likely to be sufficient in the majority of patients with candiduria and CB.

Revised guidelines on management of antenatal hydronephrosis

Widespread antenatal screening has resulted in increased detection of anomalies of the kidneys and urinary tract. The present guidelines update the recommendations published in 2000. Antenatal hydronephrosis (ANH) is transient and resolves by the third trimester in almost one-half cases. The presence of oligohydramnios and additional renal or extrarenal anomalies suggests significant pathology. All patients with ANH should undergo postnatal ultrasonography; the intensity of subsequent evaluation depends on anteroposterior diameter (APD) of the renal pelvis and/or Society for Fetal Urology (SFU) grading. Patients with postnatal APD exceeding 10 mm and/or SFU grade 3-4 should be screened for upper or lower urinary tract obstruction and vesicoureteric reflux (VUR). Infants with VUR should receive antibiotic prophylaxis through the first year of life, and their parents counseled regarding the risk of urinary tract infections. The management of patients with pelviureteric junction or vesicoureteric junction obstruction depends on clinical features and results of sequential ultrasonography and radionuclide renography. Surgery is considered in patients with increasing renal pelvic APD and/or an obstructed renogram with differential renal function <35-40% or its subsequent decline. Further studies are necessary to clarify the role of prenatal intervention, frequency of follow-up investigations and indications for surgery in these patients.

The reproducibility of measurements of differential renal function in paediatric 99mTc-MAG3 renography

OBJECTIVES

The aims of this study were to establish the reproducibility of estimates of differential renal function (DRF) obtained using the software supplied by different vendors, assess the effects of age, glomerular filtration rate (GFR) and degree of asymmetry of renal function on reproducibility and ascertain whether the software gives the same estimates of DRF.

METHODS

A stratified sample of 172 renograms covering a wide range of DRF estimates, age and renal function was drawn from an electronic archive containing raw data from 1416 renograms. The renograms were processed by one operator using seven different methods, five times for each method. For each renogram and each method the DRF for the left kidney and difference between the maximum and minimum of the five estimates of DRF were calculated.

RESULTS

There were differences in reproducibility among the seven methods [Friedman analysis of variance, χ(2)(N=172, d.f.=6)=367.0, P=0.0001]. Reproducibility was good with all methods in most children. The appreciable minority in whom reproducibility was not as good tended to be less than 6 months old or had GFRs below 90 ml/min/1.73 m(2) or both. The median of the DRF estimates of the left kidney obtained using the seven methods differed [Friedman analysis of variance, χ(2)(N=172, d.f.=6)=284.7, P<0.0001]. The largest difference between any two methods was 5%.

CONCLUSION

Although reproducibility was good in the majority of children, an appreciable minority showed poor reproducibility, which could impact clinical decision making. It is essential that these studies be identified. This can be done by processing each renogram several times, ideally using different methods. Those with poorer reproducibility tended to be less than 6 months old or to have a low GFR.

iRENEX: a clinically informed decision support system for the interpretation of ⁹⁹mTc-MAG3 scans to detect renal obstruction

PURPOSE

Decision support systems for imaging analysis and interpretation are rapidly being developed and will have an increasing impact on the practice of medicine. RENEX is a renal expert system to assist physicians evaluate suspected obstruction in patients undergoing mercaptoacetyltriglycine (MAG3) renography. RENEX uses quantitative parameters extracted from the dynamic renal scan data using QuantEM™II and heuristic rules in the form of a knowledge base gleaned from experts to determine if a kidney is obstructed; however, RENEX does not have access to and could not consider the clinical information available to diagnosticians interpreting these studies. We designed and implemented a methodology to incorporate clinical information into RENEX, implemented motion detection and evaluated this new comprehensive system (iRENEX) in a pilot group of 51 renal patients.

METHODS

To reach a conclusion as to whether a kidney is obstructed, 56 new clinical rules were added to the previously reported 60 rules used to interpret quantitative MAG3 parameters. All the clinical rules were implemented after iRENEX reached a conclusion on obstruction based on the quantitative MAG3 parameters, and the evidence of obstruction was then modified by the new clinical rules. iRENEX consisted of a library to translate parameter values to certainty factors, a knowledge base with 116 heuristic interpretation rules, a forward chaining inference engine to determine obstruction and a justification engine. A clinical database was developed containing patient histories and imaging report data obtained from the hospital information system associated with the pertinent MAG3 studies. The system was fine-tuned and tested using a pilot group of 51 patients (21 men, mean age 58.2 ± 17.1 years, 100 kidneys) deemed by an expert panel to have 61 unobstructed and 39 obstructed kidneys.

RESULTS

iRENEX, using only quantitative MAG3 data agreed with the expert panel in 87 % (34/39) of obstructed and 90 % (55/61) of unobstructed kidneys. iRENEX, using both quantitative and clinical data agreed with the expert panel in 95 % (37/39) of obstructed and 92 % (56/61) of unobstructed kidneys. The clinical information significantly (p < 0.001) increased iRENEX certainty in detecting obstruction over using the quantitative data alone.

CONCLUSION

Our renal expert system for detecting renal obstruction has been substantially expanded to incorporate the clinical information available to physicians as well as advanced quality control features and was shown to interpret renal studies in a pilot group at a standardized expert level. These encouraging results warrant a prospective study in a large population of patients with and without renal obstruction to establish the diagnostic performance of iRENEX.

Guidelines for standard and diuretic renogram in children

Special consideration needs to be given to children who undergo dynamic renography. The Paediatric Committee of the European Association of Nuclear Medicine has updated the previous guidelines. Details are provided on how to manage the child, the equipment, and the acquisition and processing protocols. The pitfalls, difficulties and controversies that are encountered are also discussed, as well as the interpretation of the results.

The International Atomic Energy Agency software package for the analysis of scintigraphic renal dynamic studies: a tool for the clinician, teacher, and researcher

Under the auspices of the International Atomic Energy Agency, a new-generation, platform-independent, and x86-compatible software package was developed for the analysis of scintigraphic renal dynamic imaging studies. It provides nuclear medicine professionals cost-free access to the most recent developments in the field. The software package is a step forward towards harmonization and standardization. Embedded functionalities render it a suitable tool for education, research, and for receiving distant expert's opinions. Another objective of this effort is to allow introducing clinically useful parameters of drainage, including normalized residual activity and outflow efficiency. Furthermore, it provides an effective teaching tool for young professionals who are being introduced to dynamic kidney studies by selected teaching case studies. The software facilitates a better understanding through practically approaching different variables and settings and their effect on the numerical results. An effort was made to introduce instruments of quality assurance at the various levels of the program's execution, including visual inspection and automatic detection and correction of patient's motion, automatic placement of regions of interest around the kidneys, cortical regions, and placement of reproducible background region on both primary dynamic and on postmicturition studies. The user can calculate the differential renal function through 2 independent methods, the integral or the Rutland-Patlak approaches. Standardized digital reports, storage and retrieval of regions of interest, and built-in database operations allow the generation and tracing of full image reports and of numerical outputs. The software package is undergoing quality assurance procedures to verify the accuracy and the interuser reproducibility with the final aim of launching the program for use by professionals and teaching institutions worldwide.

Urinary biomarkers in prenatally diagnosed unilateral hydronephrosis

The introduction of prenatal ultrasonography as a screening method entails an increasing number of infants diagnosed with prenatal hydronephrosis. Ureteropelvic junction obstruction accounts for 35% of prenatal hydronephrotic cases. Urinary tract obstruction that occurs during early kidney development affects renal morphogenesis, maturation and growth, and in the most severe cases this will ultimately cause renal insufficiency. A major challenge in the clinical management of these patients is to preserve renal function by selection of the 15%-20% who require early surgical intervention, leaving those for whom watchful waiting may be appropriate because of spontaneous resolution/stabilization without significant loss of renal function. Today, this requires medical surveillance, including repetitive invasive diuretic renograms relying on arbitrary threshold values, and therefore there is a need for non-arbitrary, non-invasive urinary biomarkers that may be used as predictors for renal structural changes and/or decreasing renal function, and thereby provide the surgeon with more clear indications for surgical intervention. In this review, we summarize the currently well-known facts about urinary biomarkers in ureteropelvic junction obstruction concerning renal function, and we also suggest potential novel urinary biomarkers.

Relative renal function with MAG-3 and DMSA in children with unilateral hydronephrosis

AIM

Tc-99m DMSA renal cortical scan is a reference method for determining relative renal function (RRF). Tc-99m MAG-3 is also recommended for the estimation of RRF, particularly in young children. The aims of this study were to compare MAG-3 and DMSA RRF estimations and to assess the reproducibility of these estimations in children with unilateral hydronephrosis.

METHODS

We reviewed MAG-3 and DMSA scans of 19 children with unilateral hydronephrosis and a normal contralateral unit. All were imaged with 2 agents within 3 months. MAG-3 RRF was calculated using 2 different time intervals (1-2 and 2-3 min) and perirenal C-type region of background activity. No background correction method was used in the calculation of DMSA RRF. All data were processed twice by two independent operators.

RESULTS

In the repeated estimates of MAG-3 RRF, the maximum mean intra-observer and inter-observer differences were 0.9% (SD 1.7%) and 1.4% (SD 3.3%), respectively. Intra-method analysis showed statistically significant agreement between repeated measures of RRF for two agents as well as for two operators (intra-class cross-correlation coefficients of early and later phase of MAG-3 and DMSA RRF values were 0.979, 0.993 and 0.996 for operator 1, and 0.986, 0.973 and 0.995 for operator 2, respectively; p < 0.001). There were statistically significant correlations between the MAG-3 and DMSA RRF estimations (r = 0.763/0.766 at 1-2 min, 0.835/0.825 at 2-3 min for the repeated measures of RRF for operator 1, and 0.812/0.793 and 0.83/0.89 for operator 2, respectively; p < 0.01, Pearson). Each scan classified as normal or abnormal according to RRF values inter-method analysis showed statistically significant agreement between MAG-3 and DMSA RRF estimations (Kappa statistics). However, there was a slight disagreement between the methods especially in infants and cases with higher grade of hydronephrosis, when 5% difference in estimations and supranormal estimates of RRF were taken into consideration.

CONCLUSION

Although DMSA and MAG-3 RRF estimations demonstrated a statistically significant correlation with good reproducibility in children with unilateral hydronephrosis, overall the finding of surprising estimates of kidney function with MAG-3 calls attention to the existence of some problems especially in infants and in those with higher grades of hydronephrotic kidneys.

Perfusion computed tomography could be a new tool for single-session imaging of ureteric obstructive pathology: an experimental study in rats

BACKGROUND/PURPOSE

Perfusion imaging redefines computed tomography (CT) as a technique that can now depict vascular physiology in addition to detailed anatomy. The major clinical applications of perfusion CT are in acute stroke and oncology. Currently, there are very limited data on the application of perfusion CT in urology. The aim of the present study is to investigate the potential value of perfusion CT in anatomic and functional evaluation of obstruction in a single session on experimental hydronephrosis model in rats. Thus, we evaluate the perfusion CT in a new clinical application.

METHODS

Twenty-eight rats were randomly allocated into 4 groups each consisting of 7 rats. At the third week of experimental intervention, postoperative renogram curves and perfusion parameters of the right kidneys' cortex and pelvis were assessed by CT. The right ureter was sutured as proximal complete obstruction in group 1, as distal complete obstruction in group 2, and as proximal partial obstruction in group 3. Group 4 served as the sham control group. Computed tomography was performed with single-slice tomography. Dynamic examination was performed with the help of perfusion software through contrast-enhanced tomography examination.

RESULTS

In all study groups, the aorta time/density curves showed a rapid increase after a rapid decrease, and the duration to reach peak concentration in the normal kidney cortex was observed to be later than the aorta as expected. In groups 1, 2, and 3, the duration to reach peak concentration lengthened and the peak concentration values decreased. The time/density curves gradually increased as a result of the accumulation of the contrast agent in the pelvis, and a peak was observed at the end of the procedure in all study groups. In groups 1, 2, and 3, a statistically significant decrease (P = .01, P = .01, and P = .01, respectively) was observed in the peak concentration values of the contrast agent in comparison to group 4. The flow and blood volume values gradually decreased as the grade of the obstruction increased and the localization of the obstruction or grade of obstruction moved closer to the kidney.

CONCLUSION

In conclusion, perfusion CT technique, performed in a single session, is a useful method for anatomic visualization, together with functional evaluation, in the diagnosis of ureteric obstructive pathology of experimental hydronephrosis model.

Results of a practical protocol for management of prenatally detected hydronephrosis due to ureteropelvic junction obstruction

INTRODUCTION

Several algorithms exist for the management of prenatally diagnosed hydronephrosis due to ureteropelvic junction obstruction (UPJO). We utilize a conservative and practical approach emphasizing observation, with less frequent use of renal flow scans (RFS). We reviewed the results of 143 pediatric patients with congenital UPJO managed at our institution, focusing on surveillance and selective utilization of RFS, according to a standardized protocol.

MATERIALS AND METHODS

Charts of all infants with prenatally detected UPJO treated surgically or followed conservatively according to our protocol were reviewed. Patients were initially evaluated with ultrasound (US), voiding cystourethrogram, and RFS. Successive follow-up was with interval US. RFS was reserved for those with worsening hydronephrosis or that which failed to improve on US by 1 year. Radiographic studies and operative reports were examined. Gender, side of UPJO, degree of hydronephrosis, mode of management, and current status of the patients were noted.

RESULTS

The records of 143 patients and a total of 198 renal units (RU) were reviewed. The male:female ratio was 2.7. UPJO was unilateral in 88 (61%) patients and occurred more frequently on the left side (68%). Obstruction was bilateral in 55 (39%) patients. Initial US grade of hydronephrosis was Grade 1 in 56 RU (28%), Grade 2 in 51 RU (26%), Grade 3 in 50 RU (25%) and Grade 4 in 41 RU (21%). 178 RU (90%) were followed conservatively, while open dismembered pyeloplasty was the initial therapeutic approach in 20 RU (10%). The mean age at the time of surgery was 15.95+/-14.60 weeks (range 2-60). Indications included low differential renal function (DRF) (n=12), absence of tracer clearance from the renal pelvis (n=2), parental preference (n=3), and acute renal failure (n=3). Postoperative course was uneventful during 33.43+/-33.53 months (range 2-120) with favorable US and RFS results. In conservatively managed patients, mean follow-up time was 14.94+/-14.35 months (range 1.5-142). Spontaneous resolution of hydronephrosis was observed in 87 RU (49%), while 10 RU (5.6%) eventually required surgery for worsening appearance or function on US or RFS, respectively (n=8), symptom development (n=3), and/or parental preference due to persistently prolonged T1/2 (n=4). Seventy-two RU (40.4%) remain under surveillance with improvement (47.2%) or stable hydronephrosis (47.2%) in 94.4%. Decreased DRF occurred in 1 RU. Nine RU (5%) were lost to follow-up. With application of this algorithm, only 12% of patients underwent two or more RFS.

CONCLUSION

Pyeloplasty may be performed safely in infants when indicated; however, the majority of children with UPJO can be managed conservatively. Spontaneous resolution of hydronephrosis and/or favorable prognosis was encountered in 87% of conservatively managed RU. The use of a standard US grading system, selective utilization of follow-up renal function testing, and parental compliance are important factors in successful management.

Upper urinary tract dilatation: prenatal diagnosis, management and outcome

Upper urinary tract dilatation is one of the most common abnormalities detected on prenatal ultrasound scanning. It is commonly due to transient urine flow impairment (UFI) at the level of the pelvi-ureteric and vesico-ureteric junctions, which improves with time in most cases. It is usually in the neonatal period that the diagnosis is confirmed and during the first 18 months of life that the prognosis of the dilatation is defined.

Late recurrence of symptomatic hydronephrosis in patients with prenatally detected hydronephrosis and spontaneous improvement

PURPOSE

Most prenatal hydronephrosis improves or resolves spontaneously with conservative treatment. However, late recurrence of prenatal hydronephrosis sometimes develops after improvement. To define the need for continuous observation after improvement of hydronephrosis, long-term followup was carried out in children with prenatally diagnosed hydronephrosis.

MATERIALS AND METHODS

We retrospectively evaluated 344 cases initially presenting between July 1991 and June 2004 with prenatally detected hydronephrosis that persisted postnatally. Subjects underwent periodic assessment of hydronephrosis using ultrasonography and diuretic renography. Indications for surgery were associated symptoms, enlarged renal pelvis, worsening hydronephrosis on sequential ultrasonography and decrease in differential renal function greater than 5%. Mean duration of followup was 10.1 years.

RESULTS

Of the 394 kidneys followed nonoperatively 4 (1%) displayed worsened hydronephrosis after spontaneous improvement. Initial grade of hydronephrosis was grade I in 1 patient, grade II in 1, grade III in 1 and grade IV in 1. On serial ultrasonographic followup hydronephrosis worsened to grade IV in 3 kidneys and to grade III in 1 kidney. Mean patient age at worsening of hydronephrosis was 40 months (range 22 to 60). All 4 patients presented with clinical symptoms. All patients who underwent pyeloplasty displayed no symptoms, and had improved hydronephrosis after pyeloplasty.

CONCLUSIONS

Prenatally detected hydronephrosis can worsen after spontaneous postnatal improvement. Long-term followup is not required after improvement of prenatal hydronephrosis. However, pediatric urologists need to tell the parents that the child should undergo ultrasonography if clinical symptoms develop.

The fate of prenatally diagnosed primary nonrefluxing megaureter: do we have reliable predictors for spontaneous resolution?

OBJECTIVES

To compare predictive values of current morphologic parameters with congenital renal damage associated with severe megaureter.

METHODS

A retrospective analysis was performed using records of 37 patients (50 megaureters) referred before birth for a primary megaureter. Mean follow-up was 26 months (range, 1 to 8 years).

RESULTS

Dilatation resolved spontaneously in 46 of 50 ureters. Only 4 of 37 patients required surgery (10.8%) after a mean follow-up of 58 months (range, 32 to 80 months). Average time to resolution was 24 months (range, 1 to 82 months) and was independent from sex, side, and bilaterality. A weak correlation was found with initial anteroposterior pelvic diameter, ureteral diameter, and separate function at renogram. A significant correlation (P <0.02) was found between megaureter type and time elapsed to spontaneous resolution. As far as differential function was concerned, mean values were significantly lower among type III megaureters, which had the lowest rate of resolution.

CONCLUSIONS

The fate of severe megaureter seems strongly influenced by congenital renal damage secondary to a developmental abnormality of the ureteric bud. A poor resolution rate has to be expected in these cases; surgery must be reserved for symptomatic cases but has no influence on pre-existing renal damage.

Antenatally detected hydronephrosis

The strategy of management of children with hydronephrosis has considerably changed as a result of the development of ultrasound techniques, allowing a prenatal detection. Hydronephrosis is defined as a dilation of the renal collecting system, and several entirely different clinical entities can be considered this general heading, whereas early detection may have a different impact depending on the entity considered. The present work aims to describe a certain number of these clinical entities, to discuss the strategic options of management that are proposed, and to evaluate the role of medical imaging, in particular the radionuclide approach. Congenital ureteropelvic junction anomaly, vesicoureteral reflux, posterior urethral valves, and duplex kidney will be successively considered. Multicystic dysplastic kidney disease, although not classified as hydronephrosis, will be mentioned because it may be mistaken for hydronephrosis.

The prognostic value of relative renal function greater than 51% in the pelvi-ureteric junction-obstructed kidney on 99mtechnetium mercaptoacetyltriglycine study

OBJECTIVE

Obstructed kidneys with relative function (RRF) estimates >50% are occasionally noted in (99m)technetium mercaptoacetyltriglycine renal studies. It is thought that increased RRF might confer some benefit and/or permit delayed intervention. We compared the RRF and absolute renal function, as defined by effective renal plasma flow (ERPF), of obstructed kidneys in the ranges >51%, 40%-50% and <40% RRF before and after pyeloplasty.

METHODS

Twenty children, median age 13.5 months (range 3 weeks-126 months), satisfied criteria for the diagnosis of PUJ obstruction and estimated function >51% (group 1). Their pre- and post-intervention data were compared with 21 children, median age 2 months (range 1 week-126 months), with PUJ obstruction and 40%-50% RRF (group 2); and 21, median age 6 months (range two days-110 months), with RRF below 40% (group 3). Kidneys showing signs of continuing obstruction after surgery were excluded.

RESULTS

Final ERPF was negatively related to age: younger children, and those with a higher preoperative ERPF, recovered better than older children and those with a lower ERPF (p<0.05). Pre- and postoperative mean ERPF in group 1 was 76 (range 21-203) and 102 (6-240) ml/min/1.73 msq respectively. In group 2, these values were 75.2 (30-187) and 130.9 (44-306) ml/min/1.73 msq, and they were 42.6 (5-179) and 80.2 (17-205) ml/min/1.73 msq in group 3. When adjustment was made for preoperative ERPF, there was no evidence that RRF grouping was related to ERPF outcome. The postoperative ERPF of seven of 20 kidneys from group 1 (>51%) was lower than the ERPF before surgery compared to 2/21 in group 2 and 4/21 in group 3, but these differences were not statistically significant (p=0.25).

CONCLUSIONS

Most kidneys in each functional range improved when obstruction was relieved. An RRF >51% in the obstructed kidney was not always prognostically beneficial, and may be a warning of impending decompensation in a minority.

Delayed decrease in differential renal function after successful pyeloplasty in children with unilateral antenatally detected hydronephrosis

AIM

The aim of this study was to evaluate functional outcome of congenital hydronephrotic kidney.

METHODS

The records of consecutive children who underwent pyeloplasty for unilateral prenatally detected ureteropelvic junction obstruction were reviewed. Renal function was assessed renographically before and after surgery. Mean follow-up period was 100 months.

RESULTS

Sufficient pre- and postoperative data were available for 60 children. Differential renal function (DRF) improved in 14 (23%) and decreased in nine (15%) of 60 patients in the early postoperative period. DRF improved in seven (18%) and decreased in 13 (34%) of 38 patients at the end of follow-up. Five of 14 patients with increased DRF at early postoperative scan returned to the preoperative level at the end of follow-up. No patients with decreased DRF at early postoperative scan showed any recovery in DRF and progressive decrease was seen in four of nine children.

CONCLUSIONS

The DRF was not stable in some patients after successful pyeloplasty. In some patients impairment of renal function came to be apparent with time. Improvement of DRF may be a transient phenomenon seen in the early postoperative period. To avoid overestimation of functional recovery, long-term follow-up with delayed renographic evaluation is recommended.

Clinical utility of ureteral jets: disparate opinions

BACKGROUND AND PURPOSE

Many renal/bladder ultrasound scans at our institution include evaluation of ureteral jets, often regardless of the indication for the study. Such jets often are absent in normal volunteers. Because these jets are of unclear clinical significance, we sought to determine if urologists and radiologists nationally agree on the clinical utility of ureteral jets.

MATERIALS AND METHODS

A three-item survey was mailed electronically to a randomly selected group of urologists and radiologists asking about the physician's practice pattern and opinion of the clinical relevance of ureteral jets by percentage and on the Likert scale. Using the unpaired Student's t-test, the responses of the groups were compared.

RESULTS

Responses were available from 177 physicians. Statistically significant differences were noted between urologists and radiologists for all three questions. Radiologists reported that 50% of ultrasonograms evaluate ureteral jets, compared with 29% for urologists (P < 0.01). Whereas radiologists "somewhat agreed" (2.01) that ureteral jets were clinically relevant, urologists were "indifferent" (2.77) to their clinical relevance (P < 0.01). The two groups also differed on the question of whether a routine ultrasound study should include evaluation of ureteral jets.

CONCLUSIONS

Urologists and radiologists disagreed on both the necessity for evaluating ureteral jets and their clinical relevance. On the basis of jet frequency and a review of the literature, accurate evaluation of jets requires a minimum of 10 minutes. The cost of this time should be considered in light of the requesting physician's opinion of the clinical relevance of the results. Until further evidence supports their value, evaluation of jets should be excluded from routine renal/bladder sonography.

Pediatric applications of renal nuclear medicine

This review should be regarded as an opinion based on personal experience, clinical and experimental studies, and many discussions with colleagues. It covers the main radionuclide procedures for nephro-urological diseases in children. Glomerular filtration rate can be accurately determined using simplified 2- or 1-blood sample plasma clearance methods. Minor controversies related to the technical aspects of these methods concern principally some correction factors, the quality control, and the normal values in children. However, the main problem is the reluctance of the clinician to apply these methods, despite the accuracy and precision that are higher than with the traditional chemical methods. Interesting indications are early detection of renal impairment, hyperfiltration status, and monitoring of nephrotoxic drugs. Cortical scintigraphy is accepted as a highly sensitive technique for the detection of regional lesions. It accurately reflects the histological changes, and the interobserver reproducibility in reporting is high. Potential technical pitfalls should be recognized, such as the normal variants and the difficulty in differentiating acute lesions from permanent ones or acquired lesions from congenital ones. Although dimercaptosuccinic acid scintigraphy seems to play a minor role in the traditional approach to urinary tract infection, recent studies suggest that this examination might influence the treatment of the acute phase, the indication for chemoprophylaxis and micturating cystography, and the duration of follow-up. New technical developments have been applied recently to the renogram: tracers more appropriate to the young child, early injection of furosemide, late postmicturition and gravity-assisted images and, finally, more objective parameters of renal drainage. Pitfalls mainly are related to the interpretation of drainage on images and curves. Dilated uropathies represent the main indication of the renogram, but the impact of this technique on the management of the child is, in a great number of cases, still a matter of intense controversy. Direct and indirect radionuclide cystography are interesting alternatives to the radiograph technique and should be integrated into the process of diagnosis and follow-up of vesicoureteral reflux.