Sonographic Renal Parenchymal Measurements for the Evaluation and Management of Ureteropelvic Junction Obstruction in Children

Comparison of early surgical and conservative therapy in children with ureteropelvic junction obstruction

BACKGROUND

Ureteropelvic junction obstruction is a relatively common urologic problem in children. Most cases present with pelvicaliceal dilatation in antenatal period. Historically most UPJO cases were treated with surgical procedures, but recently many of these children have been treated by nonsurgical observational plans. We compared the outcome of children with UPJO treated in surgical and observational ways.

METHODS

In a retrospective study, we assessed the medical history of patients diagnosed as UPJO, march 2011 to march 2021. The case definition was based on grade 3-4 hydronephrosis and obstructive pattern in dynamic renal isotopes can. Patients were put into two groups; Group 1 children were treated with a surgical procedure, and group 2 patients without any surgical procedure for at least a six months' period after diagnosis. We assessed long-term events and improvement of obstruction.

RESULTS

Seventy-eight children (mean age 7.32mo., 80% male) enrolled in the study, 55 patients in group one and 23 as group 2. Severe hydronephrosis was the problem of 96% of all patients significantly led to 20% in group 1 and 9% in group 2 (P < 0.001). Severe kidney involvement was observed at 91% in group 1 and 83% in group 2, decreased to 15% and 6%, respectively (P < 0.001). There were no significant differences in sonographic and functional improvement between the two intervention groups. Long-term prognostic issues; growth, functional impairment, and hypertension were not different between the two groups, but group 1 children experienced more recurrence of UTI than group 2 patients.

CONCLUSION

Conservative management is as effective as early surgical treatment in the management of infants with severe UPJO.

Sonographic follow-up after pyeloplasty: a large, retrospective cohort analysis

PURPOSE

Routine scintigraphy after surgery for uretero-pelvic junction obstruction (UPJO) is discouraged, making ultrasound the preferred option for follow up. Yet, interpretation of sonographic parameters is rarely straightforward.

METHODS

We reviewed 111 cases including 97 pyeloplasty (52 open, 45 laparoscopic) and 14 pyelopexy during a 7-year period. Pre- and postoperative pelvic antero-posterior diameter (APD), cortical thickness (CT) and pelvis/cortex ratio (PCR) was measured serially.

RESULTS

85% were free of symptoms by 1 year. Only 11% had complete resolution of hydronephrosis. Eleven (10.4%) needed a redo procedure. Mean reduction in APD was 32.6%, 45.8%, and 51.7% at 6 weeks, 3 and 6 months respectively. CT increased by an average 55.9%, 75.6% and 107.6% while PCR reduced by 6.9, 8.0 and 8.8 at given intervals. Comparison of open and laparoscopic procedures showed no significant difference. Review of failed pyeloplasty showed failure of reduction in APD (APD > 3 cm or < 25% reduction) and PCR (PCR > 4) as early indicators for failure.

CONCLUSION

Both APD and PCR are reliable indicators of success and failure following pyeloplasty while CT alone is not as useful. Laparoscopic procedures are non-inferior to standard open surgery.

Ultrasonographic reference values and a simple yet practical formula for estimating average kidney length in Japanese children

Background

The assessment of kidney size is essential for treating kidney disease. However, there are no reliable and sufficiently robust ultrasonographic reference values or prediction formulas for kidney length in Japanese children, based on a sufficient number of participants.

Methods

We retrospectively analyzed kidney measurements by ultrasonography in children aged 18 years or younger from eight facilities throughout Japan between January 1991 and September 2018. Detailed reference values were developed by aggregating the left and right kidneys of boys and girls separately. Simple and practical reference values were developed by combining all the data from left and right kidneys and boys and girls. The estimation formulas for the average value and lower limit of the normal range for kidney length were developed based on regression analysis.

Results

Based on the aggregated kidney length data of 1984 participants (3968 kidneys), detailed reference values and simple reference values for kidney length were determined. From the regression analysis, the formula for calculating the average kidney length was generated as “kidney length (cm) = body height (m) × 5 + 2”, and that for predicting the lower limit of normal kidney length in children under 130 cm was calculated as “lower limit (cm) = 0.85 × [body height (m) × 5 + 2]”.

Conclusion

Detailed ultrasonographic reference values of kidney length for Japanese children and simple reference values and estimation formulas for daily practice have been established.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10157-022-02205-0.

Compensatory Hypertrophy in Paediatric Patients with a Unilateral Ureteropelvic Junction Obstruction

Background

Compensatory hypertrophy is common in children with solitary functioning kidney, but it is unknown whether it also develops in children with unilateral partial reduction of kidney function.

Objective

The aim of this study was to assess whether children with a unilateral ureteropelvic junction obstruction (UPJO) show compensatory growth of the unaffected kidney. Furthermore, we investigated whether the length of the unaffected kidney was related to the degree of split kidney function lost and other possible risk factors. Lastly, we studied a possible relationship with signs of kidney injury.

Design, setting, and participants

We retrospectively analysed clinical information from 194 children with a unilateral UPJO who participated in the Aetiologic research into Genetic and Occupational/environmental Risk factors for Anomalies in children (AGORA) data- and biobank. Data on kidney length, split kidney function, and other factors possibly associated with kidney length were extracted from electronic patient records.

Outcome measurements and statistical analysis

Pearson’s correlation coefficients between the split kidney function and unaffected kidney length were calculated. Multivariable logistic regression analyses were performed to identify factors associated with kidney length and signs of kidney injury.

Results and limitations

Most children with a UPJO had an unaffected kidney length above the reference for age at the end of follow-up (median age 6.5 yr). A correlation with split kidney function was present only in children with a split kidney function of ≥60% in the unaffected kidney (r = 0.41). Aside from split kidney function, UPJO side was the only determinant of kidney length, while no associations between kidney length and kidney injury were identified.

Conclusions

Compensatory growth was visible in most children with a UPJO after sufficient follow-up time and was correlated with split kidney function in children with a severe UPJO. Contralateral kidney length provided no clear prognostic value for developing kidney injury. Studies with more patients and additional biomarkers of kidney injury are needed to further personalise care.

Patient summary

Children with obstruction of urine outflow in one kidney often had a larger contralateral kidney. However, the size of this kidney could not be used to predict which children would develop kidney injury.

Ultrasound-Based Renal Parenchymal Area and Kidney Function Decline in Infants With Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract are the leading cause of chronic kidney disease in children. Noninvasive imaging biomarkers that predict chronic kidney disease progression in early infancy are needed. We performed a pilot study nested in the prospective Chronic Kidney Disease in Children cohort study to determine the association between renal parenchymal area (RPA) on first post-natal renal ultrasound and change in estimated glomerular filtration rate (eGFR) in children with congenital anomalies of the kidney and urinary tract. Among 14 participants, 78.6% were males, the median age at the time of the ultrasound was 3.4 months (interquartile range, 1.3-7.9 mo), and the median total RPA z-score at baseline was -1.01 (interquartile range, -2.39 to 0.52). After a median follow-up period of 7.4 years (interquartile range, 6.8-8.2 y), the eGFR decreased from a median of 49.4 mL/min per 1.73 m² at baseline to 29.4 mL/min per 1.73 m², an annual eGFR percentage decrease of -4.68%. Lower RPA z-scores were correlated weakly with a higher annual decrease in eGFR (Spearman correlation, 0.35; 95% confidence interval, -0.25 to 0.76). This pilot study shows the feasibility of obtaining RPA from a routine ultrasound and suggests that a lower baseline RPA may be associated with a greater decrease in eGFR over time. Further studies with larger patient cohorts are needed to confirm this association.

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.

The utility of renal sonographic measurements in differentiating children with high grade congenital hydronephrosis

INTRODUCTION

Current grading systems for hydronephrosis include a subjective determination of parenchymal 'thickness' and suffer from poor reliability. Use of more objective ultrasonographic measurements including medullary pyramidal thickness (PT) may be useful in augmenting current grading systems by decreasing subjectivity and enhancing prognostic ability.

OBJECTIVE

To evaluate the utility of PT measurements in patients with SFU grades 3 and 4 hydronephrosis, we assessed the: 1) the inter-rater reliability of PT measurements, 2) the correlation between relative renal function on nuclear renal scan and PT, and 3) the pyeloplasty predictive ability of PT alone and in combination with SFU grade and/or other sonographic measurements in multivariate statistical models.

STUDY DESIGN

We retrospectively reviewed 110 children with SFU grade III and IV hydronephrosis. Most patients presented with a history of prenatally detected hydronephrosis at a median age (IQR) of 1.7 months (0.6-5.2). Sixty-two kidneys were followed without operative intervention while 63 underwent pyeloplasty. Indications for surgery included an obstructive drainage pattern with a T1/2 > 20 min on diuretic renal scan in addition to decreased relative renal function less than 40%, increasing hydronephrosis on serial ultrasounds, and/or a decline in relative renal function >10% on serial renal scans. The median age at the time of pyeloplasty was 5.7 months (2.8-13.7). The median time from initial presentation to final follow-up for all patients was 28 months (18.3-44.6). The PT, APD, and renal length were measured on sonographic images. The inter-rater reliability for SFU grading was only fair whereas it was excellent for PT measurements. Receiver operating characteristic (ROC) curves were generated for inclusive multivariate models for prediction of pyeloplasty with and without SFU grade.

DISCUSSION AND CONCLUSIONS

PT is a reliable and useful measurement to characterize the hydronephrotic kidney parenchyma and a PT > 3 mm occurs significantly more frequently in patients with a DRF ≥ 45% (p = 0.0056). PT alone was predictive of subsequent pyeloplasty (AUC = 0.781). A novel pyeloplasty predictive score (PPS) using only objective measurements including PT, APD, and renal length was more accurate than a PPS that incorporated SFU grade (AUC of 0.885 and 0.866, respectively). Utilization of PT ≤ 3 mm as a criterion for 'thinned parenchyma' in the SFU, UTD, and other hydronephrosis grading systems should be considered if confirmed by additional studies.

Renal length z-score for the detection of dysfunction in children with solitary functioning kidney

AIM

To evaluate whether renal length z-scores predict renal dysfunction in children with a solitary functioning kidney (SFK).

METHODS

In a single-centre retrospective cohort of children with SFK, we correlated body mass index z-scores, extracellular volume and lean body mass to renal length z-scores. We grouped these z-scores to other markers of renal dysfunction (proteinuria, hypertension, extracellular volume and abnormal estimated glomerular function rate [eGFR]) and analysed renal length z-score with multivariate analysis, receiver-operated characteristics (ROC) plots and Youden's index to determine an appropriate cut-off.

RESULTS

111 children had a median follow-up 5.08 years, eGFR 80.8 mL/min/1.73 m² , and age at last follow-up 7.4 (3.8-13.4 years). The median renal length z-scores of those without any renal dysfunction (n = 37, 25.1%) were greater (+3.66, interquartile range 3.02-4.47) than those with renal dysfunction (median 3.11, interquartile range 1.76-4.11, P = .0107, Mann-Whitney test). Using a cut-off of z-score of >+1.911, the odds ratio for having no renal dysfunction was 0.07 (95% CI 0.002-0.459, P = .0010). However, accuracy of the renal length z-score was poor (ROC curve 0.6488).

CONCLUSION

In this cohort of children with SKF, using the renal length z-score as a biomarker of renal dysfunction at 7 years of age is not recommended.

Utility of ultrasound elastography in postoperative follow-up of children with unilateral ureteropelvic junction obstruction

Introduction:

We aimed to determine whether shear wave velocity (SWV) on ultrasound elastography is useful in follow-up of children with ureteropelvic junction obstruction (UPJO) following pyeloplasty.

Methods:

Consecutive children with unilateral UPJO who were co-operative for elastography (n = 31) were included. SWV of normal kidney was used as control, and it was compared with that of the affected kidney (UPJO) in the same patient. They were followed up with elastography at 3 months and elastography + renogram at 6 months postoperatively. In patients with a static renogram at 6 months, the study was repeated at 1 year. Patient outcomes were classified as improved at 6 months, static at 6 months, and worsened at 1 year based on ultrasound and renogram findings. The SWV was compared between the different outcomes.

Results:

Thirty-one children with a median age of 8.5 years were studied (m:f = 29:2; L:R = 22:9). The mean SWV was significantly higher (3.21 m/s) in UPJO kidney compared to the SWV (2.72 m/s) found in normal kidney (P = 0.011). The mean SWV was significantly less at 3 months (2.73 m/s) and 6 months (2.57 m/s) postoperative follow-up (P = 0.018 and P= 0.001). Among the patients who improved, the mean SWV was 2.65 m/s. This SWV was significantly raised (3.57 m/s) in patients whose condition remained static (P = 0.006) and even higher (4.36 m/s) in those who worsened (P = 0.001).

Conclusions:

SWV was significantly higher in UPJO compared to normal kidneys in children. It is useful in assessing postoperative resolution, and a rising velocity can be useful as an early marker of recurrence in UPJO.

Can measurement of the foetal renal parenchymal thickness with ultrasound be used as an indirect measure of nephron number?

Chronic kidney disease continues to be under recognised and is associated with a significant global health burden and costs. An adverse intrauterine environment may result in a depleted nephron number and an increased risk of chronic kidney disease. Antenatal ultrasound was used to measure the foetal renal parenchymal thickness (RPT), as a novel method to estimate nephron number. Foetal renal artery blood flow was also assessed. This prospective, longitudinal study evaluated the foetal kidneys of 102 appropriately grown and 30 foetal growth-restricted foetuses between 20 and 37 weeks gestational age (GA) to provide vital knowledge on the influences foetal growth restriction has on the developing kidneys. The foetal RPT and renal artery blood flow were measured at least every 4 weeks using ultrasound. The RPT was found to be significantly thinner in growth-restricted foetuses compared to appropriately grown foetuses [likelihood ratio (LR) = 21.06, P ≤ 0.0001] and the difference increases with GA. In foetuses with the same head circumference, a growth-restricted foetus was more likely to have a thinner parenchyma than an appropriately grown foetus (LR = 8.9, P = 0.0028), supporting the principle that growth-restricted foetuses preferentially shunt blood towards the brain. No significant difference was seen in the renal arteries between appropriately grown and growth-restricted foetuses. Measurement of the RPT appears to be a more sensitive measure than current methods. It has the potential to identify infants with a possible reduced nephron endowment allowing for monitoring and interventions to be focused on individuals at a higher risk of developing future hypertension and chronic kidney disease.

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

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

A clinical predictive model of renal injury in children with isolated antenatal hydronephrosis

Background

Antenatal hydronephrosis (ANH) affects ∼1-5% of pregnancies. The aim of this study was to develop a clinical prediction model of renal injury in a large cohort of infants with isolated ANH.

Methods

This is a longitudinal cohort study of 447 infants with ANH admitted since birth between 1989 and 2015 at a tertiary care center. The primary endpoint was time until the occurrence of a composite event of renal injury, which includes proteinuria, hypertension and chronic kidney disease (CKD). A predictive model was developed using a Cox proportional hazards model and evaluated by C-statistics.

Results

Renal pelvic dilatation (RPD) was classified into two groups [Grades 1-2 (n = 255) versus Grades 3-4 (n = 192)]. The median follow-up time was 6.4 years (interquartile range 2.8-12.5). Thirteen patients (2.9%) developed proteinuria, 6 (1.3%) hypertension and 14 (3.1%) CKD Stage 2. All events occurred in patients with RPD Grades 3-4. After adjustment, three covariables remained as predictors of the composite event: creatinine {hazard ratio [HR] 1.27, [95% confidence interval (CI) 1.05-1.56]}, renal parenchyma thickness at birth [HR 0.78(95% CI 0.625-0.991)] and recurrent urinary tract infections [HR 4.52 (95% CI 1.49-13.6)]. The probability of renal injury at 15 years of age was estimated as 0, 15 and 24% for patients assigned to the low-risk, medium-risk and high-risk groups, respectively (P < 0.001).

Conclusion

Our findings indicate an uneventful clinical course for patients with Society for Fetal Urology (SFU) Grades 1-2 ANH. Conversely, for infants with SFU Grades 3-4 ANH, our prediction model enabled the identification of a subgroup of patients with increased risk of renal injury over time.

Predictive Factors of Contralateral Operation after Initial Pyeloplasty in Children with Antenatally Detected Bilateral Hydronephrosis Due to Ureteropelvic Junction Obstruction

OBJECTIVES

This study was performed to analyze the predictive factors of a contralateral operation after initial pyeloplasty in patients with antenatally detected bilateral ureteropelvic junction obstruction.

METHODS

Patients with prenatally diagnosed bilateral ureteropelvic junction obstruction who underwent initial pyeloplasty (aged <12 months at initial pyeloplasty) were offered to participate in the study. Patients were recruited from January 2012 to December 2015. The anteroposterior renal pelvic diameter, parenchymal thickness, and calyceal dilatation were evaluated. Predictive factors of contralateral pyeloplasty after initial unilateral pyeloplasty were also examined.

RESULTS

In total, 82 patients were included in the study (mean age, 2.8 months). Among all patients who underwent initial pyeloplasty, additional contralateral pyeloplasty was required in 11 patients (13.4%). The outcome of contralateral hydronephrosis was assessed as resolution, persistence, or surgery. The median anteroposterior renal pelvic diameter and calyceal dilatation were significantly different among the groups (p < 0.001). Calyceal dilatation of ≥10 mm and a calyceal dilatation/parenchymal thickness ratio of ≥5 strongly suggested the likelihood of a contralateral operation.

CONCLUSIONS

In most patients with bilateral ureteropelvic junction obstruction, improvement or resolution of contralateral hydronephrosis following initial unilateral pyeloplasty can be expected. Patients with contralateral calyceal dilatation >10 mm and the calyceal dilatation/parenchymal thickness ratio >5 are at higher risk of surgery.

Acoustic radiation force impulse (ARFI) elastography in the evaluation of renal parenchymal stiffness in patients with ureteropelvic junction obstruction

PURPOSE

To investigate the role of acoustic radiation force impulse (ARFI) elastography in the detection of renal parenchymal damage in kidneys with and without ureteropelvic junction obstruction (UPJO).

METHODS

Twenty-five pediatric patients with a diagnosis of UPJO who underwent surgery and 15 pediatric patients with conservatively managed UPJO were prospectively evaluated with ARFI elastography. Sixteen healthy volunteers constituted the control group. Shear wave velocity (SWV) measurements in the upper, mid, and lower poles of the affected kidney were performed. SWV values of kidneys based on presence of UPJO and hydronephrosis grade were compared. The correlation of SWV values with residual renal function obtained from diethylenetriaminepentaacetic acid or mercaptoacetyltriglycine-3 renal scan was evaluated.

RESULTS

Significantly, higher SWV values were found in control kidneys compared to kidneys affected by UPJO. The median SWVs were 2.82 (2.51-3.07) m/s for the control kidneys and 2.36 (2.09-2.53) m/s for the kidneys in the UPJO group (p < 0.001). When UPJO patients were grouped according to the grade of hydronephrosis, grade 0 hydronephrotic kidneys [2.35 (2.11-2.50) m/s] and grade 3-4 hydronephrotic kidneys [1.86 (1.96-2.25) m/s] had significantly lower SWV values compared to grade 1-2 hydronephrotic kidneys [2.62 (2.37-2.90) m/s] (p < 0.05).

CONCLUSIONS

ARFI as a noninvasive, radiation-free procedure for evaluating parenchymal stiffness may prove useful in the diagnostic work-up and follow-up of children with UPJO-induced renal disease.