Simple, age-based formula for predicting renal length in children

Early diagnosis of solitary functioning kidney: comparing the prognosis of kidney agenesis and multicystic dysplastic kidney

BACKGROUND

Individuals with congenital solitary functioning kidney (SFK) are at an increased risk of kidney damage. According to some studies, the risk is higher in unilateral kidney agenesis (UKA) than in unilateral multicystic dysplastic kidney (UMCDK). We hypothesized that with early detection of children with UKA and UMCDK, there would be no difference in the presence of hypertension, proteinuria, and reduced glomerular filtration rate (GFR) between UKA and UMCDK.

METHODS

Based on a long-term follow-up protocol, we evaluated a cohort of 160 children followed from birth for SFK (84 with UKA and 76 with UMCDK) detected by prenatal or routine neonatal ultrasound screening. Hypertension, proteinuria, and reduced GFR were monitored as markers of kidney damage. We compared the characteristics and outcomes of the subgroups of children with UKA and UMCDK.

RESULTS

GFR was reduced in 42 (26.2%) children, of whom 41 showed only mild reduction. Hypertension and proteinuria were found in 22 (13.8%) and 14 (8.8%) children, respectively. Combined kidney damage was present in 57 (35.6%) children. The UMCDK and UKA subgroups differed in GFR at final examination, with UMCDK patients being significantly more likely to have normal GFR compared to UKA patients (82% vs. 67%; p = 0.039).

CONCLUSIONS

One third of the children showed signs of SFK damage, albeit mild. Patients with UKA had reduced GFR significantly more often than those with UMCDK, but did not differ in the rates of hyperfiltration injury or congenital anomalies of the kidneys and urinary tract (CAKUT) in SFK.

Uncovering risk factors for kidney injury in children with a solitary functioning kidney

Children with a solitary functioning kidney (SFK) have an increased risk of kidney injury. The exact risk of and risk factors for kidney injury remain unknown, which impedes personalized care. Here, we recruited a nationwide multicenter cohort of 944 patients with SFK to get more insight into this by consenting patients born in 1993-2020 and diagnosed with congenital or acquired SFK before adulthood. The median follow-up was 12.8 years and four indications of kidney injury were studied: urine protein-creatinine ratios, blood pressure, estimated glomerular filtration rate and use of anti-hypertensive/proteinuric medication. For each indicator except medication use, separate cut-off values for any injury and severe injury were used. Survival analyses indicated that at 18 years of age, any or severe kidney injury were present in 75% and 39% of patients with congenital SFK, respectively. Risk factors for kidney injury included kidney agenesis as cause of the SFK, anomalies in the SFK, and high body mass index at last follow-up. Kidney agenesis and being overweight were specifically associated with proteinuria and high blood pressure, whereas anomalies in the SFK were associated with reduced estimated glomerular filtration rates. The high prevalence of kidney injury in patients with SFK emphasizes the need for long-term follow-up, in which lifestyle is an important topic to address. More research into the etiological role of risk factors will help to translate our findings into individualized care strategies. Thus, our study shows that a significant proportion of children with SFK will develop kidney injury over time.

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.

A reappraisal of pediatric abdominal surface anatomy

Surface anatomy is fundamental to clinical and surgical practices. As the surface anatomy varies with age, the purpose of this study is to provide age-standardized surface markings for the abdomen in children. A total of 155 abdominal computed tomography scans of healthy children aged 0-18 years were categorized into six groups, and the surface anatomy of the major vascular structures, solid viscera, and anatomical planes in the abdomen was analyzed. The vertebral levels of the celiac trunk, superior mesenteric artery, and hepatic portal vein formation were higher in the youngest age group, whereas the levels of the inferior mesenteric artery, formation of the inferior vena cava, and renal arteries did not differ with age. The right kidney lay between T12 and L3 and the left at T11-L3; however, both kidneys were in lower positions in younger children. The spleen was most commonly located between the 8th and 11th ribs except in toddlers. In all age groups, the hepatic portal vein formation was within the transpyloric plane and the aortic bifurcation was above the supracristal plane. In vivo reassessment of the surface anatomy enables the substantial variability of surface landmarks to be highlighted. This study demonstrates that taking account of age-related variations will increase the accuracy and therefore the clinical relevance of surface anatomy.

Reduction in urinary angiotensinogen levels and improvement of proteinuria by renin-angiotensin system blockade in pediatric chronic kidney disease patients with very low birth weight

BACKGROUND

Children with low birth weight (LBW) have an increased risk of developing chronic kidney disease (CKD), and no effective strategies have been established to prevent the progression of CKD in these patients. Urinary angiotensinogen (UAGT) may represent a useful marker of intrarenal renin-angiotensin system (RAS) activation, which has been suggested to play a critical role in the development of hypertension and CKD. Herein, we conducted a prospective study to determine whether RAS blockade is beneficial for suppressing the progression of CKD in children with LBW, using UAGT as a surrogate marker of renal impairment.

METHODS

Nine children with CKD (stages: 1-2) who had very low birth weight (VLBW; < 1500 g) were started on RAS blockade with candesartan. We measured blood pressure and laboratory parameters, including urinary concentrations of angiotensinogen, protein, albumin, creatinine (Cr), and estimated glomerular filtration rate (eGFR), before and after candesartan treatment.

RESULTS

Birth weight was 712 g (range, 536-800 g). Age at evaluation was 11.6 years (range, 10.3-15.6 years). After candesartan treatment for 47.6 ± 25.0 months, the UAGT to urinary Cr ratio decreased from 61.9 ± 44.7 to 16.8 ± 14.4 μg/g (p = 0.015). The urinary protein to Cr and albumin to Cr ratios also decreased (p = 0.008 and p = 0.012, respectively), whereas there was no significant change in eGFR.

CONCLUSIONS

RAS blockade reduced UAGT levels and improved proteinuria/albuminuria in children with CKD who had VLBW. Suppression of intrarenal RAS activity may slow the progression of CKD in children with LBW.

Is renal scintigraphy really a necessity in the routine diagnosis of congenital solitary kidney?

BACKGROUND

For a definitive diagnosis of congenital solitary kidney, renal scintigraphy is suggested as being the gold standard of ruling out ectopic functioning renal tissue, possibly missed by ultrasound. The aim of our study was to test ultrasonography precision in comparison with renal scintigraphy on a larger cohort of congenital solitary kidneys.

METHODS

We performed a retrospective unicenter study of children with congenital solitary kidney with no contralateral tissue, who were treated in the period from 1980 to 2017. The findings in children who underwent both abdominopelvic ultrasound and nuclear renal scintigraphy were compared and the accuracy of ultrasound was assessed.

RESULTS

99 children met the inclusion criteria of congenital solitary kidney confirmed with abdominopelvic ultrasound and nuclear renal scintigraphy. The children were predominantly male (61.6%), and the congenital solitary kidney was largely right-sided (55.5%). In 97 cases (98%), ultrasound correctly predicted the absence of functional renal tissue on one side in the renal fossa or in an ectopic location (pelvis or ipsilateral side). The calculated accuracy of abdominopelvic ultrasound in diagnosing congenital solitary kidney was therefore 98%.

CONCLUSIONS

Our findings confirm that abdominopelvic ultrasound alone is accurate enough to diagnose congenital solitary kidney. It gives enough information for consideration if further radiological evaluation is still needed.

Sonographic Growth Charts for Kidney Length in Normal Korean Children: a Prospective Observational Study

Kidney length is the most useful parameter for clinical measurement of kidney size, and is useful to distinguish acute kidney injury from chronic kidney disease. In this prospective observational study of 437 normal children aged between 0 and < 13 years, kidney length was measured using sonography. There were good correlations between kidney length and somatic values, including age, weight, height, and body surface area. The rapid growth of height during the first 2 years of life was intimately associated with a similar increase in kidney length, suggesting that height should be considered an important factor correlating with kidney length. Based on our findings, the following regression equation for the reference values of bilateral kidney length for Korean children was obtained: kidney length of the right kidney (cm) = 0.051 × height (cm) + 2.102; kidney length of the left kidney (cm) = 0.051 × height (cm) + 2.280. This equation may aid in the diagnosis of various kidney disorders.

Configuring a Better Estimation of Kidney Size in Obese Children and Adolescents

Background

Obesity ignites numerous health and psychosocial problems and is associated with various comorbidities. Body mass index (BMI) is also independently associated with improved risk for numerous kidney disorders. As renal length is considered a vital parameter in the clinical assessment of renal patients, normal renal length has to be defined in accordance to BMI.

Objectives

The aim of this study was to define normal kidney length in obese children, comparing ultrasound measurements of the kidney length in obese and non-obese children and adolescents, in order to reduce unnecessary evaluations for nephromegaly.

Patients and Methods

Fifty obese children and adolescents and 50 non-obese children and adolescents, aged 1-19 years, were selected from patients of pediatric clinics in two hospitals (Rasoul-e-Akram and Shahid Fahmideh) in Tehran between June 2010 and 2012. After the nephrologist’s and endocrinologist’s approval, the largest longitudinal renal dimension was measured in deep inspiration position by abdomino-pelvic ultrasonography in both groups.

Results

It was revealed that both kidneys in obese group were significantly larger than in control group (P = 0.044 and 0.040, respectively). Obesity status, height and age were proven to be significant and independent predictors of length of both kidneys. In both groups length of left kidney was significantly larger than that of right kidney (P < 0.001).

Conclusions

A specific standard cut-point limit or norm gram has to be formulated for obese children and adolescents in order to facilitate the diagnosis of kidney diseases, including organomegaly, in these patients.

Transient renal enlargement in pediatric hematopoietic cell transplant recipients

Age-dependent renal length tables are routinely used when interpreting pediatric ultrasound. Standard renal length tables may not be accurate for HCT patients due to treatment effects on kidney size. The purpose of this study was to determine whether renal size changes from expected lengths based on age after HCT in the absence of other markers of renal disease. Four hundred and fifty renal measurements were made on 101 patients who underwent HCT between 2006 and 2010. Renal length was measured at 1-90 days pre-HCT and at 0-30, 31-90, 91-180, and 181+ days post-HCT. Values were compared with normal renal length tables. Average post-HCT renal lengths were greater than established normative renal length data within every age group. Age-adjusted average renal lengths measured at 0-30 and 31-90 days post-transplantation were significantly larger than pre-HCT renal lengths, with relative increases of 6.9% (4.5, 9.4; p < 0.001) and 3.9% (1.4, 6.4; p = 0.003), respectively. Average renal length did not differ significantly after 90 days post-transplantation. HCT patients may have larger kidneys in the absence of renal disease. Awareness of the potential phenomenon of transient renal enlargement following HCT can prevent misdiagnosis and eliminate unnecessary diagnostic evaluations, interventions, anxiety, resource allocation, and financial costs.

Kidney size estimation in Korean children with Technesium-99m dimercaptosuccinic acid scintigraphy

PURPOSE

Renal size is an important indicator to determine adequate organ growth in children. The aim of this study was to estimate renal size with Technesium-99m dimercaptosuccinic acid (DMSA) scan and propose a simple formula for predicting renal length in normal Korean children.

METHODS

This study included 346 children (148 boys and 198 girls; age range, 1 month to 17 years) in whom renal length was measured using the DMSA scan. Patients with anatomical renal abnormalities or acute pyelonephritis were excluded. Children were divided into two groups: 214 children (61.8%) were less than a year old (group 1) and 132 (38.2%) were ≥1 year (group 2).

RESULTS

Renal length was larger on the left side than the right side, and there was no significant gender-related difference in renal length. We propose the following formula for renal length based on the analysis of the 346 children in our study: the formula was as follows: 4.682×age (month)(0.137), R(2) =0.780. In group 1, the formula was renal length (cm)=0.127×age (month)+5.144, R(2) =0.354, and in group 2, the formula was 0.334×age (year)+6.477, R(2) =0.829.

CONCLUSION

It is difficult to establish simple formulae in infants (R(2) =0.354). Therefore, further studies including relevant variables are needed for this age group. We proposed formulae to estimate renal length in Korean children over 1 year of age by using the DMSA scan.

Kidney growth and renal functions under the growth hormone replacement therapy in children

OBJECTIVE

The aim of this study was to investigate the kidney growth and renal functions in children receiving recombinant human growth hormone (rhGH) treatment.

MATERIALS AND METHODS

A total of 37 children who received rhGH for 1.5 years before the study was started and 48 healthy controls were included at first evaluation. Hormone levels were determined and kidney sizes were measured by ultrasound. Kidney functions were assessed by serum creatinine and estimated glomerular filtration rate (eGFR). After 3 years of first evaluation, 23 patients were re-assessed.

RESULTS

Kidney sizes were found to be lower in rhGH received children compared with controls at first evaluation (p<0.05). Significant positive correlations were found between anthropometric measurements and kidney length and kidney volume (p<0.05). Height was the most significant predictor of kidney volume in rhGH received children (p<0.001). After 3-years of follow-up significantly increases were found in kidney length and volume compared with the first measurements (p<0.05). Increase percentage of body height was similar to increasing percent of kidney length and liver long axis (14.2%, 11.7.1% and 7.7%, respectively, p>0.05). Although no abnormal renal function test results were found at first and second evaluations; rhGH received children had significantly lower eGFR, at first evaluation, compared with controls; however, renal functions significantly increased after 3 years of follow-up (p<0.05).

CONCLUSIONS

In conclusion, effect rhGH treatment on kidney growth is parallel to growth in body height and other visceral organs. A 3-years rhGH treatment resulted in significant increases in renal functions.

Renal growth in isolated methylmalonic acidemia

PURPOSE

We sought to predict renal growth based on clinical and metabolic parameters in patients with isolated methylmalonic acidemia, a group of disorders associated with chronic kidney disease.

METHODS

Fifty patients with methylmalonic acidemia, followed from 2004 to 2011, were classified by molecular genetics and studied using a combined cross-sectional and longitudinal design that included renal ultrasound examinations, anthropometric measurements, and metabolic phenotyping. Renal length was compared with that of healthy controls and modeled to other clinical parameters using multiple-regression analyses.

RESULTS

Comparisons with age-matched controls showed that renal length in subjects with methylmalonic acidemia was significantly decreased (P < 0.05). Stepwise regression modeling found that combinations of height, serum cystatin C, and serum methymalonic acid concentrations best predicted kidney size. The regression equations used to generate methylmalonic acidemia kidney nomograms were renal length (cm) = 6.79 + 0.22 × age for the controls and 6.80 + 0.09 × age for the methylmalonic acidemia cohort (P < 0.001; constant and slope).

CONCLUSION

Renal length, reflective of kidney growth, significantly decreased in patients with methylmalonic acidemia over time as compared with controls and was predictable with select clinical parameters. Cystatin C and serum methylmalonic acid concentrations were highly correlated with smaller kidneys and decreased renal function in this patient population.

Are there long-term effects of extracorporeal shockwave lithotripsy in paediatric patients?

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Extracorporeal shockwave lithotripsy is effective for the treatment of paediatric renal stones with favourable short-term safety. Extracorporeal shockwave lithotripsy for treatment of paediatric renal stones is also safe for the kidney and the child on long-term follow-up.

OBJECTIVE

To evaluate the long-term effects of extracoporeal shockwave lithotripsy (SWL) for treatment of renal stones in paediatric patients.

PATIENTS AND METHODS

A database of paediatric patients who underwent SWL monotherapy for treatment of renal stones from September 1990 through to January 2009 was compiled. This study included only patients with follow-up for more than 2 years. The long-term effects of SWL were evaluated at the last follow-up with measurement of patients' arterial blood pressure, estimation of random blood sugar and urine analysis. The results of diastolic blood pressure were plotted against a standardized age reference curve. The treated kidney was examined by ultrasonography for measurement of renal length and detection of stones. The measured renal lengths were plotted against age-calculated normal renal lengths in healthy individuals.

RESULTS

The study included 70 patients (44 boys (63%) and 26 girls) with mean age at the time of SWL 6.5 ± 3.6 years (range 1-14). The mean follow-up period was 5.2 ± 3.6 years (range 2.1-17.5). The mean age at last follow-up was 11.7 ± 5.3 years (range 4.4-27.5). No patients developed hypertension or diabetes. Only one treated kidney was smaller than one standard deviation of the calculated length. The cause of this was obstruction by a stone in the pelvic ureter 3 years after SWL.

CONCLUSION

The long-term follow-up after SWL for treatment of renal stones in paediatric patients showed no effect on renal growth and no development of hypertension or diabetes.

Abdominopelvic ultrasound: a cost-effective way to diagnose solitary kidney

PURPOSE

Solitary kidneys are detected on approximately 1 of 1,500 prenatal ultrasounds and during evaluation for other urological complaints. Although renal scintigraphy is currently the gold standard for confirming the diagnosis and ruling out renal ectopia, scintigraphy is associated with radiation exposure, placement of an intravenous line and sedation. We hypothesize that ultrasonography alone is sufficient to detect solitary kidneys and that confirmatory renal scintigraphy is unnecessary.

MATERIALS AND METHODS

We reviewed the records of children with a solitary kidney who underwent ultrasound and nuclear scintigraphy at our institution from 2001 to 2010. Radiological findings were compared to assess the accuracy of ultrasound in diagnosing solitary kidneys. Costs were calculated based on 2011 Medicare global reimbursement.

RESULTS

A total of 25 children met the inclusion criteria of undergoing ultrasound and renal scintigraphy (dimercapto-succinic acid or mercaptoacetyltriglycine scan). The majority of cases were male (16, 64%) and left sided (17, 68%). Median age was 9 days (range 1 day to 11.6 years) at first ultrasound and 4.4 months (3 weeks to 12 years) at first renal scintigraphy. In 24 patients ultrasound correctly diagnosed a solitary kidney as confirmed by nuclear scan. In 1 patient ultrasound suggested a pelvic kidney but repeat ultrasound was negative, as was dimercapto-succinic acid scan. The diagnostic accuracy of ultrasound was 96%. Medicare reimbursement for dimercapto-succinic acid scan (CPT 78700) is $460 to $720 ($222 plus $240 for radiotracer plus $260 for anesthesia, if used).

CONCLUSIONS

Our findings suggest that ultrasonography alone is sufficient to make the diagnosis of solitary kidney. Omitting routine renal scintigraphy saves approximately $460 to $720 per case, and avoids radiation and discomfort without sacrificing diagnostic accuracy.