Renal Parenchyma to Hydronephrosis Area Ratio (PHAR) as a Predictor of Future Surgical Intervention for Infants With High-grade Prenatal Hydronephrosis

Clinical characteristics of patients with prenatal hydronephrosis in early postnatal period: a single center retrospective study

BACKGROUND

The study aims to investigate the clinical characteristics of early postnatal period in children with prenatal hydronephrosis (HN) in our single center for 8 years.

STUDY DESIGN

The clinical data of 1137 children with prenatal HN from 2012 to 2020 were retrospectively analyzed in our center. Variables of our study mainly included different malformations and urinary tract dilation (UTD) classification, and main outcomes were recurrent hospitalization, urinary tract infection (UTI), jaundice, and surgery.

RESULTS

Among the 1137 children with prenatal HN in our center, 188 cases (16.5%) were followed-up in early postnatal period, and 110 cases (58.5%) were found malformations. The incidence of recurrent hospitalization (29.8%) and UTI (72.5%) were higher in malformation, but the incidence of jaundice (46.2%) was higher in non-malformation(P < 0.001). Furthermore, UTI and jaundice were higher in vesicoureteral reflux (VUR) than those in uretero-pelvic junction obstruction (UPJO) (P < 0.05). Meanwhile, Children with UTD P2 and UTD P3 were prone to recurrent UTI, but UTD P0 was prone to jaundice (P < 0.001). In addition, 30 cases (16.0%) of surgery were all with malformations, and the surgical rates of UTD P2 and UTD P3 were higher than those of UTD P0 and UTD P1 (P < 0.001). Lastly, we concluded that the first follow-up should be less than 7 days, the first assessment should be 2 months, and the follow up should be at least once every 3 months.

CONCLUSION

Children with prenatal HN have been found many malformations in early postnatal period, and with high-grade UTD were more prone to recurrent UTI, even to surgery. So, prenatal HN with malformations and high-grade UTD should be followed up in early postnatal period regularly.

Deep-learning segmentation of ultrasound images for automated calculation of the hydronephrosis area to renal parenchyma ratio

Purpose

We investigated the feasibility of measuring the hydronephrosis area to renal parenchyma (HARP) ratio from ultrasound images using a deep-learning network.

Materials and Methods

The coronal renal ultrasound images of 195 pediatric and adolescent patients who underwent pyeloplasty to repair ureteropelvic junction obstruction were retrospectively reviewed. After excluding cases without a representative longitudinal renal image, we used a dataset of 168 images for deep-learning segmentation. Ten novel networks, such as combinations of DeepLabV3+ and UNet++, were assessed for their ability to calculate hydronephrosis and kidney areas, and the ensemble method was applied for further improvement. By dividing the image set into four, cross-validation was conducted, and the segmentation performance of the deep-learning network was evaluated using sensitivity, specificity, and dice similarity coefficients by comparison with the manually traced area.

Results

All 10 networks and ensemble methods showed good visual correlation with the manually traced kidney and hydronephrosis areas. The dice similarity coefficient of the 10-model ensemble was 0.9108 on average, and the best 5-model ensemble had a dice similarity coefficient of 0.9113 on average. We included patients with severe hydronephrosis who underwent renal ultrasonography at a single institution; thus, external validation of our algorithm in a heterogeneous ultrasonography examination setup with a diverse set of instruments is recommended.

Conclusions

Deep-learning-based calculation of the HARP ratio is feasible and showed high accuracy for imaging of the severity of hydronephrosis using ultrasonography. This algorithm can help physicians make more accurate and reproducible diagnoses of hydronephrosis using ultrasonography.

Ability of volume measures of hydronephrosis to predict need for surgery and evaluate renal function in children with ureteropelvic junction obstruction

OBJECTIVE

To explore the efficacy of quantitative renal volume measures on magnetic resonance urography images in predicting need for surgery among children with ureteropelvic junction obstruction and their ability to evaluate renal function.

METHODS

A total of 88 cases of hydronephrosis in 50 patients were collected between 1 April 2018 and 31 March 2020, including 30 operated kidney and 58 unoperated kidney cases. Clinical data were collected, and quantitative analysis of magnetic resonance urography was performed. Renal volume, hydronephrosis volume and the volume ratio of hydronephrosis (hydronephrosis volume/renal volume) were measured and calculated. We analyzed the relationships between the above indices in the two groups and compared these with renal function.

RESULTS

Compared with the unoperated kidney group, hydronephrosis volume, renal volume and hydronephrosis volume/renal volume of the operated kidney group increased significantly. Hydronephrosis volume (area under the curve 0.972, 95% confidence interval 0.943-1.000; P < 0.001) and hydronephrosis volume/renal volume (area under the curve 0.968, 95% confidence interval 0.939-0.998; P < 0.001) were superior to ultrasonography and renal function examination in predicting the probability of surgery, and their sensitivity values (hydronephrosis volume/renal volume: 96.67%; hydronephrosis volume: 93.33%) were higher than those of the renal function test (50%). There was a significant difference among different renal function groups in the pairwise comparison of hydronephrosis volume and hydronephrosis volume/renal volume (P < 0.05).

CONCLUSION

Quantitative volume measures of hydronephrosis by magnetic resonance urography had a greater ability to predict need for surgery than ultrasonography and dynamic renal imaging, and it can be used as method by which to evaluate surgery. Hydronephrosis volume and hydronephrosis volume/renal volume have greater predictive ability, and play an important role in the deterioration of renal function.

Personalized application of machine learning algorithms to identify pediatric patients at risk for recurrent ureteropelvic junction obstruction after dismembered pyeloplasty

PURPOSE

To develop a model that predicts whether a child will develop a recurrent obstruction after pyeloplasty, determine their survival risk score, and expected time to re-intervention using machine learning (ML).

METHODS

We reviewed patients undergoing pyeloplasty from 2008 to 2020 at our institution, including all children and adolescents younger than 18 years. We developed a two-stage machine learning model from 34 clinical fields, which included patient characteristics, ultrasound findings, and anatomical variation. We fit and trained with a logistic lasso model for binary cure model and subsequent survival model. Feature importance on the model was determined with post-selection inference. Performance metrics included area under the receiver-operating-characteristic (AUROC), concordance, and leave-one-out cross validation.

RESULTS

A total of 543 patients were identified, with a median preoperative and postoperative anteroposterior diameter of 23 and 10 mm, respectively. 39 of 232 patients included in the survival model required re-intervention. The cure and survival models performed well with a leave-one-out cross validation AUROC and concordance of 0.86 and 0.78, respectively. Post-selective inference showed that larger anteroposterior diameter at the second post-op follow-up, and anatomical variation in the form of concurrent anomalies were significant model features predicting negative outcomes. The model can be used at https://sickkidsurology.shinyapps.io/PyeloplastyReOpRisk/ .

CONCLUSION

Our ML-based model performed well in predicting the risk of and time to re-intervention after pyeloplasty. The implementation of this ML-based approach is novel in pediatric urology and will likely help achieve personalized risk stratification for patients undergoing pyeloplasty. Further real-world validation is warranted.

Urine Biomarkers Combined With Ultrasound for the Diagnosis of Obstruction in Pediatric Hydronephrosis

Introduction: To establish the efficacy of ultrasound (US) combined with urine biomarkers in differentiating patients who require surgical management from those who do not, avoiding invasive investigations. Materials and Methods: From February 2019 to February 2021, all pediatric patients who presented with hydronephrosis were selected for the study. All renal units (RU) were evaluated by US, and fresh frozen voided urine samples were collected at the time of inclusion. Hydronephrosis grade was evaluated by the Society for Fetal Urology (SFU) and an alternative grading system (AGS). Patients who had high-grade hydronephrosis on US were referred to renal scan (RS) or intervention, when there was an increase of dilatation in subsequent follow-up images. Fresh frozen urine from the control group with no history of renal diseases and no renal anomalies on US was collected. We compared differences of US parameters combined with urine biomarkers between surgically and non-surgically managed patients and between the groups of patients when they were stratified by different RS findings and analyzed whether urinary biomarkers give any additional value to US. Instead of the anterior-posterior diameter (APD), we used its ratio with mid-parenchymal thickness. The additional efficacy of biomarkers to US was calculated when the US component was derived to a cumulative APD/mid-parenchymal ratio. Results: Sixty-four patients with hydronephrosis were prospectively included in the study accounting for a total of 81 patient visits and 162 RUs evaluated. A control group of 26 patients was collected. The mean age at inclusion in the hydronephrosis group was 43.7(±45.5) months, and a mean age in a control group was 61.2(±41.3) months. The cumulative APD/mid-parenchymal ratio combined with urinary albumin, β2 microglobulin (β2-M), and urinary neutrophil gelatinase-associated lipocalcin may have a better performance in the prediction of surgical intervention than the cumulative APD/mid-parenchymal ratio alone (p = 0.1). The best performance to detect the increased tissue transit time and obstructive curve on RS was demonstrated by the β2-M creatinine ratio. An increased cumulative APD/mid-parenchymal ratio with biomarkers together had a fairly good sensitivity and specificity for detection of DRF < 40%. Conclusions: According to our data, the APD/mid-parenchymal ratio alone has good efficacy in prediction of surgery and abnormal RS findings especially when combined with urine biomarkers.

Experience of a tertiary-level urology center in the clinical urological events of rare and very rare incidence. IV. Urological surprises: 2. Clinically visible giant hydronephrosis in adults: Is there a significant function?

Background

Giant hydronephrosis is rare with a controversy about the complete loss of renal functions. Our objective is to present our center’s experience with the management of cases of clinically visible giant hydronephrosis considering the potential residual functions. Our study is a retrospective case series of clinically visible giant hydronephrosis which was managed during the period July 2001–June 2016. Demographic and clinical variables were studied with specific considerations to the potential residual functions.

Results

Of more than 82,000 urological interventions, only 47 cases (0.057%) were operated upon for clinically visible giant hydronephrosis. Group 1 included 21 patients (mean age = 50.43 ± 13.71 years) who were treated initially by nephrostomy tube, and group 2 included 26 patients (mean age = 42.96 ± 15.16 years) who were treated primarily by nephrectomy. The main clinical presentation was abdominal distention (61.7%), while 13 patients (27.7%) were unaware of the swellings. The commonest underlying causes of hydronephrosis were urolithiasis (68.1%) and bilharzial ureteral strictures (23.4%). The contralateral kidney was diseased in 22 cases (46.8%) including the bilateral clinically visible hydronephrosis in 7 cases (15%). Indications of placement of a nephrostomy tube included uremia, infections, and evaluation of renal functions, where 5 cases of group 1 regained significant split function ranged 14–33%.

Conclusions

Clinically visible giant hydronephrosis is an extreme form of renal dilatation with different etiologies such as urolithiasis and bilharziasis. Initial placement of a nephrostomy tube may save significant residual functions in these kidneys.

Experience of a tertiary-level urology center in the clinical urological events of rare and very rare incidence. IV. Urological surprises: 2. Clinically visible giant hydronephrosis in adults: Is there a significant function?

Background

Giant hydronephrosis is rare with a controversy about the complete loss of renal functions. Our objective is to present our center’s experience with the management of cases of clinically visible giant hydronephrosis considering the potential residual functions. Our study is a retrospective case series of clinically visible giant hydronephrosis which was managed during the period July 2001–June 2016. Demographic and clinical variables were studied with specific considerations to the potential residual functions.

Results

Of more than 82,000 urological interventions, only 47 cases (0.057%) were operated upon for clinically visible giant hydronephrosis. Group 1 included 21 patients (mean age = 50.43 ± 13.71 years) who were treated initially by nephrostomy tube, and group 2 included 26 patients (mean age = 42.96 ± 15.16 years) who were treated primarily by nephrectomy. The main clinical presentation was abdominal distention (61.7%), while 13 patients (27.7%) were unaware of the swellings. The commonest underlying causes of hydronephrosis were urolithiasis (68.1%) and bilharzial ureteral strictures (23.4%). The contralateral kidney was diseased in 22 cases (46.8%) including the bilateral clinically visible hydronephrosis in 7 cases (15%). Indications of placement of a nephrostomy tube included uremia, infections, and evaluation of renal functions, where 5 cases of group 1 regained significant split function ranged 14–33%.

Conclusions

Clinically visible giant hydronephrosis is an extreme form of renal dilatation with different etiologies such as urolithiasis and bilharziasis. Initial placement of a nephrostomy tube may save significant residual functions in these kidneys.

Best ultrasound parameter for prediction of adverse renal function outcome after pyeloplasty

OBJECTIVE

To evaluate the clinical value of preoperative ultrasound parameters for post-pyeloplasty outcomes in pediatric patients with ureteropelvic junction obstruction.

METHODS

The medical records of 187 pediatric and adolescent patients who underwent pyeloplasty as a result of ureteropelvic junction obstruction between 2010 and 2016 were retrospectively reviewed. The severity of hydronephrosis was measured by the Society for Fetal Urology grade, anteroposterior pelvic diameter, urinary tract dilation, hydronephrosis index, and the hydronephrosis area to renal parenchyma ratio at 3, 6 and 12 months. Adverse renal function outcome was defined as ≥10% decrease in postoperative differential renal function compared with preoperative values.

RESULTS

Of the 187 patients, preoperative hydronephrosis was categorized as Society for Fetal Urology grade 3 in 26 patients (13.9%) and grade 4 in 161 patients (86.1%). No surgical failures, defined as requirement of repeat surgery or deterioration of hydronephrosis grade, were noted. The mean changes in Society for Fetal Urology grade, anteroposterior pelvic diameter, urinary tract dilation and hydronephrosis area to renal parenchyma ratio showed similar trends of recovery during the follow-up period. In total, 19 patients (10.2%) showed >10% decrease in differential renal function during follow up (mean 42 months). Multivariate logistic regression analysis showed that the hydronephrosis area-to-renal parenchyma ratio was the only significant prognostic factor for adverse renal function outcome (hazard ratio 1.806, 95% confidence interval 1.210-2.859, P = 0.005). Receiver operating characteristic analysis showed that the hydronephrosis area-to-renal parenchyma ratio was the most significant predictive value (area under the curve 0.711, 95% confidence interval 0.618-0.804, P = 0.006).

CONCLUSIONS

Pediatric patients with high hydronephrosis area-to-renal parenchyma ratio values before surgery are more likely to show renal function decline after pyeloplasty.

Experience of a tertiary-level urology center in the clinical urological events of rare and very rare incidence. IV. Urological surprises: 2. Clinically visible giant hydronephrosis in adults: Is there a significant function?

Background

Giant hydronephrosis is rare with a controversy about the complete loss of renal functions. Our objective is to present our center’s experience with the management of cases of clinically visible giant hydronephrosis considering the potential residual functions. Our study is a retrospective case series of clinically visible giant hydronephrosis which was managed during the period July 2001–June 2016. Demographic and clinical variables were studied with specific considerations to the potential residual functions.

Results

Of more than 82,000 urological interventions, only 47 cases (0.057%) were operated upon for clinically visible giant hydronephrosis. Group 1 included 21 patients (mean age = 50.43 ± 13.71 years) who were treated initially by nephrostomy tube, and group 2 included 26 patients (mean age = 42.96 ± 15.16 years) who were treated primarily by nephrectomy. The main clinical presentation was abdominal distention (61.7%), while 13 patients (27.7%) were unaware of the swellings. The commonest underlying causes of hydronephrosis were urolithiasis (68.1%) and bilharzial ureteral strictures (23.4%). The contralateral kidney was diseased in 22 cases (46.8%) including the bilateral clinically visible hydronephrosis in 7 cases (15%). Indications of placement of a nephrostomy tube included uremia, infections, and evaluation of renal functions, where 5 cases of group 1 regained significant split function ranged 14–33%.

Conclusions

Clinically visible giant hydronephrosis is an extreme form of renal dilatation with different etiologies such as urolithiasis and bilharziasis. Initial placement of a nephrostomy tube may save significant residual functions in these kidneys.

Diuretic Enhanced Ultrasonography in the Diagnosis of Pyeloureteral Obstruction

Background and Objectives: To determine the value of diuretic ultrasonography for the diagnosis of obstructive hydronephrosis. Materials and Methods: Diuretic enhanced ultrasonography was used routinely as a part of examination of patients with hydronephrosis in our Department. There were 72 patients (42 males, 30 females; aged 2 months to 17 years; median age 7.07 years) with a sonoscopic diagnosis of hydronephrosis included from January 2006 until October 2011. The anteroposterior diameter (AD) of renal pelvis was measured sonoscopically before and at sixty minutes after furosemide injection. A weight-adjusted dose of 1 mg/kg of furosemide was administered intravenously. Results: Patients were operated on if pyeloureteral obstruction was suspected because of low or deteriorating differential renal function, increasing hydronephrosis or symptoms thereof. Hydronephrosis was unilateral in 61 (84.7%) and bilateral in 11 (15.3%) patients. The median AD of pelvis before furosemide injection was 22 mm in operated and 17 mm in non-operated patients (p = 0.005). Sixty minutes after furosemide injection, the AD of pelvis in operated patients was 35.5 mm and 25.8 mm in non-operated—25.8 mm (p < 0.001). Logistic regression model demonstrated that significant factors for surgery were: AD 60 min after furosemide infection and ultrasonographic parenchymal sclerosis. Conclusion: Ultrasound measurement of the AD of renal pelvis 1 h after the injection of furosemide used as an additional investigation can help in predicting obstructive hydronephrosis.

Study of the renal Parenchymal volume during the human fetal period

Objective:

To evaluate the renal parenchymal area in human fetuses, providing a descriptive analysis on the renal area development by demographic factors during the second gestational trimester.

Material and Methods:

We analyzed 84 fetuses (44 males and 40 females), for a total of 168 renal units evaluated in terms of longitudinal length, superior pole width, inferior pole width and thickness. Renal volume was calculated by ellipsoid formula. After renal pelvis dissection, length and width were evaluated; as pelvis is free of urine, we considered thickness as 1mm. Renal pelvis volume was also calculated by ellipsoid formula. Renal parenchymal area was assessed by excluding the volume of the renal pelvis from the total renal volume. We performed the statistical analysis by simple linear regression assessing the association between the variables analyzed with the fetal age.

Results:

Gestational age ranged from 12 to 23 weeks post conception. Mean renal parenchymal area of the right kidney was 666.22mm³ (45.86 to 2375.35mm³) and for the left kidney was 606.76mm3 (68.63 to 2402.57mm³). No statistical difference was observed between the sides (p-value = 0.3456) or genders (p-value = 0.07429). Linear regression between renal parenchymal volume and gestational age was positive for right kidney (y = 133.74x-1479.94 / r² = 0.4009) and left kidney (y = 149.53x-1761.59 / r² = 0.4591).

Conclusions:

The linear regression analysis indicated that renal parenchymal area correlated significantly and positively with fetal age, weight and crown-rump length with no statistical differences between gender or laterality. These growth curves provide a reference for functional volume of the kidney during fetal period.

Ultrasound evaluation for prediction of outcomes and surgical decision in fetal hydronephrosis

Fetal hydronephrosis (HY) is a frequent congenital condition, which may be detected by prenatal ultrasound. Society for Fetal Urology (SFU) and anterior-posterior diameter (APD) grading are two major grading systems based on ultrasonography. The present study aimed to assess the predictive value of the SFU and APD grades in patients with fetal HY. A total of 162 patients with 234 kidneys affected by HY were included in the present study. The SFU and APD grades were determined from the ultrasound images at 38 gestational weeks, and a 12-month follow-up was performed after birth. The associations of the SFU and APD grades with the outcome of fetal HY, including HY regression, and post-partum surgery were examined. In the present study, 16 patients with 17 kidneys were diagnosed with pathological HY, and stenosis at the ureteropelvic junction was demonstrated to be a leading cause of pathological HY. Among the 234 kidneys affected by HY, 161 kidneys were scored as SFU grade I, 57 as SFU grade II, 7 as SFU grade III and 9 kidneys as SFU grade IV. According to the APD grading system, 112 kidneys were determined as having low, 104 as having moderate and 18 as having severe HY. The SFU and APD grades were demonstrated to be independently associated with the occurrence of pathological HY by logistic regression analysis with a high diagnostic accuracy to distinguish pathological and physiological HY cases as evidenced by the results of ROC analysis. In addition, univariate and multivariate logistic regression analysis indicated that patients with spontaneous HY regression usually had low SFU and APD grades. Furthermore, the rate of surgery was increased in the group of patients with high SFU or APD grades, and these two systems were identified as independent predictors for the requirement of surgery by Kaplan-Meier analysis. Patients with pathological HY had high SFU and APD grades, and these two grading systems may be used as reliable predictors for the outcome of fetal HY, including HY regression, and post-partum surgery.

A Predictive Model of Postnatal Surgical Intervention in Children With Prenatally Detected Congenital Anomalies of the Kidney and Urinary Tract

The aim of this study was to identify predictive factors and develop a model to assess individualized risk of postnatal surgical intervention in patients with antenatal hydronephrosis. This is a retrospective cohort study of 694 infants with prenatally detected congenital anomalies of kidney and urinary tract with a median follow-up time of 37 months. The main event of interest was postnatal surgical intervention. A predictive model was developed using Cox model with internal validation by bootstrap technique. Of 694 patients, 164 (24%) infants underwent surgical intervention in a median age of 7.8 months. Predictors of the surgical intervention in the model were: baseline glomerular filtration rate, associated hydronephrosis, presence of renal damage and the severity of renal pelvic dilatation. The optimism corrected c statistic for the model was 0.84 (95%CI, 0.82-0.87). The predictive model may contribute to identify infants at high risk for surgical intervention. Further studies are necessary to validate the model in patients from other settings.

Simple visual review of pre- to post-operative renal ultrasound images predicts pyeloplasty success equally as well as geometric measurements: A blinded comparison with a gold standard

BACKGROUND

MAG3 diuretic renal scan remains the gold standard for determination of improvement in renal drainage following pyeloplasty for ureteropelvic junction obstruction. We hypothesized that (i) a change in geometric measurements between pre-operative and post-operative renal ultrasound (RUS) images and (ii) blinded simple visual review of images both would predict pyeloplasty success.

OBJECTIVE

To determine if simple visual review and/or novel geometric measurement of renal ultrasounds can detect pyeloplasty failure.

STUDY DESIGN

This study was a retrospective, blinded comparison with a gold standard. Included were children aged ≤18 years undergoing pyeloplasty at our institution from 2009 to 2015. For each kidney, representative pre-operative and post-operative RUS images were chosen. Our standard for pyeloplasty success was improved drainage curve on MAG3 and lack of additional surgery. Measurements for collecting system circularity, roundness, and renal parenchymal to collecting system area ratio (RPCSR) were obtained by three raters (Figure), who were blinded to the outcome of the pyeloplasty. Changes in geometric measurements were analyzed as a diagnostic test for MAG3-defined pyeloplasty success using ROC curve analysis. In addition, six reviewers blinded to pyeloplasty success reviewed pre-operative and post-operative images visually for improved hydronephrosis and categorized pyeloplasty as success or failure based on simple visual review of RUS.

RESULTS

Fifty-three repaired renal units were identified (50 children). There were five pyeloplasty failures, four of which underwent revision or nephrectomy. While all geometric measurements could discriminate pyeloplasty failure and success, the geometric measurements that discriminated best between pyeloplasty failure and success were change in collecting system roundness and change in RPCSR. Consensus opinion among six blinded reviewers using simple visual review had a sensitivity of 94% and PPV of 100% with respect to identifying pyeloplasty success (AUC 0.97 (95% CI 0.93-1.0)). This was not significantly different from AUC for change in roundness (p = 0.09) or change in RPCSR (p = 0.1).

DISCUSSION

Change in collecting system roundness and change in RPCSR were the most accurate geometric measurements in predicting pyeloplasty success. Simple visual review of ultrasound images for pyeloplasty success performed as well or better than geometric measurements. However, geometric measurements remain useful as a research tool or to communicate findings between clinicians.

CONCLUSIONS

Complex geometric measurements of hydronephrosis or post-operative MAG3 scans are not needed if hydronephrosis is visually significantly improved, as simple visual review is highly sensitive for detecting pyeloplasty failure.