Quantitative ultrasound renal parenchymal area correlates with renal volume and identifies reflux nephropathy

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.

Clinical predictors of chronic kidney disease in congenital lower urinary tract obstruction

Congenital lower urinary tract obstruction is associated with oligohydramnios and significant perinatal mortality and long-term chronic kidney disease. The counseling of families facing this diagnosis, especially when prenatal intervention is proposed, is fraught with ambiguity. This review aims to equip the provider with the current evidence behind the conventional and novel biomarkers predictive of chronic kidney disease. The relevant clinical predictors are categorized by when they are identified, antenatally or postnatally, and as either anatomic or chemical. They are considered for their prognostic value and the challenges in obtaining them, specifically the risk to the fetus in the case of prenatal biomarkers. Serum creatinine in infancy is the traditional chemical biomarker of kidney function and continues to be a consistent predictor of future serum creatinine. β-2 microglobulin may provide earlier information regarding fetal glomerular and tubular function and is also predictive of long-term serum creatinine. Renal parenchymal area is an anatomic surrogate of nephron mass that is used in both prenatal and postnatal settings. Understanding the anatomic and chemical biomarkers is essential for future refinement of the staging algorithm used to distinguish which patients may benefit from early in utero intervention.

Sonographic measurements for kidney length in normal Saudi children: correlation with other body parameters

BACKGROUND

Ultrasonography provides a quick assessment of visceral organ dimensions without any risk of radiation. Since many diseases can affect the kidney size, having a reliable reference for kidney length in children is valuable for clinical assessment.

OBJECTIVE

Establish normal growth curves for renal length in relation to sex, age, body weight, height, body mass index and body surface area of healthy children in Saudi Arabia.

DESIGN

Retrospective review of ultrasonography images.

SETTING

Tertiary referral hospital.

PATIENTS AND METHODS

We included all normal ultrasonography exams of renal length from full-term neonates to children ≤14 years old performed between 2003 and 2018. Data was collected retrospectively from the electronic archive and patient records.

MAIN OUTCOME MEASURES

Relationship between the longitudinal length of both kidneys and age, height, weight, body mass index and body surface area.

SAMPLE SIZE

950 patients.

RESULTS

The left kidneys were longer than the right kidneys ( P<.001). Height had the most significant correlation with kidney length (R²=0.829, P<.001 for right kidney; R²=0.831, P<.001 for left kidney). There was a consistent difference in kidney length by sex. Both kidneys were longer in males than females ( P=.031, right kidney:, P=.015, left kidney). In terms of renal growth by age, our data showed a statistically significant difference before and after 24 months of age. There was no significant difference between populations from Saudi Arabia, Hong Kong ( P=.485) and Australia ( P=.99), but the difference between Saudi and American children was significant ( P<.001). However, we did not have the data from those studies for direct comparison. The correlation plots of renal length versus age for all four countries were similar.

CONCLUSION

The tables and correlation plots generated from this study should be useful to radiology departments in assessing conditions in children ≤14 years of age that lead to changes in renal size.

LIMITATIONS

Retrospective, and there were differences in ultrasonographic techniques for patient positioning and cursor placement that can affect the reproducibility of measurements of renal length.

CONFLICT OF INTEREST

None.

Prenatal renal parenchymal area as a predictor of early end-stage renal disease in children with vesicoamniotic shunting for lower urinary tract obstruction

BACKGROUND

Vesicoamniotic shunting (VAS) and other bladder drainage techniques for fetal lower urinary tract obstruction (LUTO) have been proven to ameliorate pulmonary hypoplasia and increase survival in patients with an initial poor prognosis. Currently there are limited prognostic tools available during gestation to evaluate and predict postnatal renal function.

OBJECTIVE

The aim was to describe the prenatal growth of the renal parenchymal area (RPA) in patients with LUTO and determine its application as a predictor of renal function at one year of life.

STUDY DESIGN

The study population comprised a retrospective cohort of all infants who survived the fetal VAS to birth. Renal growth and size were measured using imageJ software to calculate the RPA in sequential prenatal ultrasounds. The parenchymal area was measured from the image of each kidney with the greatest longitudinal length. These measurements were further correlated and analyzed as a predictor of end-stage renal disease (ESRD) within the first year of life.

RESULTS

Etiologies of LUTO in the 15 male fetuses included eight posterior urethral valves, four Eagle-Barrett/prune belly syndrome, two urethral atresia, and one megacystis microcolon intestinal hypoperistalsis syndrome. All patients had patent shunts, in place, at birth. Furthermore, ultrasonographic parameters such as oligohydramnios, keyhole sign, and bladder wall thickness showed no statistical difference between groups. Renal parenchymal growth correlated with postnatal renal function in both the ESRD (r = 0.409, p = 0.018) and the non-ESRD (r = 0.657, p < 0.001) groups. Most notably, RPA during the 3rd trimester predicted ESRD with the best cut-off point determined to be 8 cm² (sensitivity, 0.714; specificity, 0.882; and positive likelihood ratio, 6.071) (Table).

DISCUSSION

Despite definitive VAS for LUTO, postnatal morbidity and mortality remain high, emphasizing the role of renal dysplasia in postnatal renal failure, in spite of urinary diversion. Renal growth statistically differs between groups in the 3rd trimester of gestation; RPA development appears stagnant in patients that developed ESRD within the first year of life. In contrast, patients that did not develop ESRD continued to have renal parenchymal growth in a linear fashion. This suggests that prenatal RPA may be predictive of postnatal ESRD.

CONCLUSIONS

RPA measurement during the prenatal period could play an important role as a non-invasive tool to predict postnatal renal function and to anticipate postnatal clinical interventions.

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

OBJECTIVE

To explore the potential value of an objective assessment, renal parenchyma to hydronephrosis area ratio (PHAR), as an early predictor of surgery.

METHODS

Initial sagittal renal ultrasound (US) images of patients prospectively entered into a prenatal hydronephrosis database from January 2008 to January 2016 with baseline Society for Fetal Urology (SFU) grades III and IV prenatal hydronephrosis, without vesicoureteral reflux, were evaluated using the National Institutes of Health-sponsored image processing software. PHAR, anteroposterior diameter, SFU grade, and urinary tract dilation risk categories were contrasted with nuclear scan data (differential renal function and drainage time [t_1/2]) and analyzed for predictive value in determining the decision to proceed with surgery by drawing receiver operating characteristic curves.

RESULTS

Out of 196 infants (162 male; 138 left sided hydronephrosis), 58 (30%) underwent surgery to address obstruction. Surgical patients compared with those managed conservatively had longer t_1/2 (60 vs 18 min; P < .01) and lower differential renal function (46 vs 50%; P = .01). Of the initial US parameters, PHAR (area under the curve = 0.816; P < .001) had a better predictive performance than anteroposterior diameter, SFU grade, or urinary tract dilation classification. PHAR values correlated with subsequent parameters obtained on nuclear scan.

CONCLUSION

PHAR is a promising parameter that can be estimated on presentation US to help predict future need for surgery in newborns with high-grade hydronephrosis.

Renal Parenchymal Area Growth Curves for Children 0 to 10 Months Old

PURPOSE

Low renal parenchymal area, which is the gross area of the kidney in maximal longitudinal length minus the area of the collecting system, has been associated with increased risk of end stage renal disease during childhood in boys with posterior urethral valves. To our knowledge normal values do not exist. We aimed to increase the clinical usefulness of this measure by defining normal renal parenchymal area during infancy.

MATERIALS AND METHODS

In a cross-sectional study of children with prenatally detected mild unilateral hydronephrosis who were evaluated between 2000 and 2012 we measured the renal parenchymal area of normal kidney(s) opposite the kidney with mild hydronephrosis. Measurement was done with ultrasound from birth to post-gestational age 10 months. We used the LMS method to construct unilateral, bilateral, side and gender stratified normalized centile curves. We determined the z-score and the centile of a total renal parenchymal area of 12.4 cm(2) at post-gestational age 1 to 2 weeks, which has been associated with an increased risk of kidney failure before age 18 years in boys with posterior urethral valves.

RESULTS

A total of 975 normal kidneys of children 0 to 10 months old were used to create renal parenchymal area centile curves. At the 97th centile for unilateral and single stratified curves the estimated margin of error was 4.4% to 8.8%. For bilateral and double stratified curves the estimated margin of error at the 97th centile was 6.6% to 13.2%. Total renal parenchymal area less than 12.4 cm(2) at post-gestational age 1 to 2 weeks had a z-score of -1.96 and fell at the 3rd percentile.

CONCLUSIONS

These normal renal parenchymal area curves may be used to track kidney growth in infants and identify those at risk for chronic kidney disease progression.

Analysis of Kidney Ultrasound Dimensions by Body Habitus and Position

PURPOSE

Renal dimensions are an important assessment of the genitourinary tract used to evaluate critical aspects of renal growth and development. Understanding the effect of patient position is important to use and interpret these parameters. In this prospective study we determined the effect of patient position and general body habitus on renal length and parenchymal area in children undergoing renal ultrasound.

MATERIALS AND METHODS

Between October 2010 and January 2011 children underwent renal ultrasound while prone and supine. Bilateral renal length and renal parenchymal area were measured. Pearson and Bland-Altman statistical analyses were used to examine correlations, measurement bias and the degree of agreement between methods.

RESULTS

Renal length measurements in both positions were complete for 201 right and 196 left kidneys. Parenchymal area measurements were complete for both kidneys in 177 children. When compared individually, supine and prone measures of renal length and parenchymal area highly correlated on Pearson analysis (greater than 0.96 and greater than 0.89, respectively). When compared by method, Bland-Altman analyses of differences vs means showed greater than 50% variance, representing wide limits of agreement with poor interrelation. Neither persistent systematic bias nor body habitus influenced results.

CONCLUSIONS

While Pearson analysis showed high correlation for supine and prone renal measurements, Bland-Altman analysis of renal length and parenchymal area demonstrated wide limits of agreement, not allowing interchangeable use of prone and supine measurements. As such, renal ultrasound should specify standardized positions and benchmarks. These results provide guidance to standardize renal ultrasound measurements when renal size is used as an indicator of kidney health.

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

PURPOSE

To correlate sonographic renal parenchymal measurements among patients with ureteropelvic junction obstruction (UPJO) labeled society of fetal urology (SFU) hydronephrosis grades 1-4 and to examine whether sonographic renal parenchymal measurements could be used to differentiate conservative vs. surgical management.

MATERIALS AND METHODS

Retrospective chart review and sonographic renal parenchymal measurements (renal length, medullary pyramid thickness, and renal parenchymal thickness) were performed in patients with SFU grades 1-4 hydronephrosis secondary to UPJO managed between 2009 and 2014. Exclusion criteria included other concomitant genitourinary pathology or incomplete follow-up. Anterior-posterior renal pelvic diameter (APRPD) and radionuclide renography were also evaluated when available.

RESULTS

One hundred four patients with UPJO underwent 244 renal and bladder ultrasound (1,464 sonographic renal parenchymal measurements in 488 kidneys). Medullary pyramid thickness and renal parenchymal thickness progressively decreased from SFU grades 1-4 (p < 0.05). A similar trend was appreciated when comparing SFU grades 1 and 2 vs. 3 and 4, as well as SFU grades 3 vs. 4 (p < 0.05). SFU grade 3 and 4 patients who underwent pyeloplasty had longer renal length in comparison to those who were managed conservatively (p < 0.02).

CONCLUSION

This is the first study that evaluates these objective, quantifiable sonographic renal parenchymal measurements in children with unilateral UPJO. These sonographic renal parenchymal measurements correlate closely with worsening of hydronephrosis graded by the SFU and APRPD classification systems. Prospective studies are needed to elucidate the role of sonographic renal parenchymal measurements in the management of children with UPJO.

Renal parenchymal area and risk of ESRD in boys with posterior urethral valves

BACKGROUND AND OBJECTIVES

Approximately 20% of boys with posterior urethral valves develop ESRD; however, few factors associated with the risk of ESRD have been identified. The objective of this study was to determine if renal parenchymal area, defined as the area of the kidney minus the area of the pelvicaliceal system on first postnatal ultrasound, is associated with the risk of ESRD in infants with posterior urethral valves.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A retrospective cohort of boys who were diagnosed with posterior urethral valves at less than 6 months of age between 1988 and 2011 and followed for at least 1 year at a free-standing children's hospital was assembled. Cox proportional hazard regression and Kaplan-Meier analysis were used to estimate the association between renal parenchymal area and time to ESRD. Cox models were adjusted for age at presentation, minimum creatinine 1 month after bladder decompression, and vesicoureteral reflux.

RESULTS

Sixty patients were followed for 393 person-years. Eight patients developed ESRD. Median renal parenchymal area was 15.9 cm(2) (interquartile range=13.0-21.6 cm(2)). Each 1-cm(2) increase in renal parenchymal area was associated with a lower risk of ESRD (hazard ratio, 0.64; 95% confidence interval, 0.42 to 0.98). The rate of time to ESRD was 10 times higher in boys with renal parenchymal area<12.4 cm(2) than boys with renal parenchymal area≥12.4 cm(2) (P<0.001). Renal parenchymal area could best discriminate children at risk for ESRD when the minimum creatinine in the first 1 month after bladder decompression was between 0.8 and 1.1 mg/dl.

CONCLUSION

In boys with posterior urethral valves presenting during the first 6 months of life, lower renal parenchymal area is associated with an increased risk of ESRD during childhood. The predictive ability of renal parenchymal area, which is available at time of diagnosis, should be validated in a larger, prospectively-enrolled cohort.

Conventional frequency ultrasonic biomarkers of cancer treatment response in vivo

BACKGROUND

Conventional frequency quantitative ultrasound in conjunction with textural analysis techniques was investigated to monitor noninvasively the effects of cancer therapies in an in vivo preclinical model.

METHODS

Conventional low-frequency (∼7 MHz) and high-frequency (∼20 MHz) ultrasound was used with spectral analysis, coupled with textural analysis on spectral parametric maps, obtained from xenograft tumor-bearing animals (n = 20) treated with chemotherapy to extract noninvasive biomarkers of treatment response.

RESULTS

Results indicated statistically significant differences in quantitative ultrasound-based biomarkers in both low- and high-frequency ranges between untreated and treated tumors 12 to 24 hours after treatment. Results of regression analysis indicated a high level of correlation between quantitative ultrasound-based biomarkers and tumor cell death estimates from histologic analysis. Applying textural characterization to the spectral parametric maps resulted in an even stronger correlation (r (2) = 0.97).

CONCLUSION

The results obtained in this research demonstrate that quantitative ultrasound at a clinically relevant frequency can monitor tissue changes in vivo in response to cancer treatment administration. Using higher order textural information extracted from quantitative ultrasound spectral parametric maps provides more information at a high sensitivity related to tumor cell death.

Body-surface-area related renal volume: a common normal range from birth to adulthood

Renal volume is an important parameter of renal development. Deviations from normal volume may indicate pathologic conditions. Thus, during childhood, the ever changing renal volumes require the continuous referral to normal volume charts in order to classify actual volumes, which is rather inconvenient. In daily practice this is frequently disregarded and kidneys are evaluated by their appearance only. Therefore, we tested the hypothesis that body surface area (BSA) and renal volume grow proportionally from birth to adulthood. We divided the renal volume of a child by its BSA to get the BSA-related renal volume (BSARV) and found no differences between left and right kidneys and a normal distribution for all kidneys regardless of the patient's age. BSARV has a common normal range for all age groups with the 10th percentile of 45 and the 90th percentile of 85 mL/m(2). 80% of all kidneys do not exceed the volume of their counterparts by more than 20%. BSARV alleviates the correct evaluation of a child's renal volume regardless of age and reveals pathological influences by the simple observation that a kidney deviates from a former percentile or z-value. This is especially valuable in the followup of kidneys with chronic diseases.