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

Antiphospholipid syndrome presenting as isolated renal vein thrombosis: a case report and review of the literature

BACKGROUND

Pediatric antiphospholipid syndrome is a rare systemic autoimmune disorder characterized by recurrent thrombotic events in the presence of antiphospholipid antibodies. Isolated right renal vein thrombosis resulting in a nonfunctional kidney is an uncommon manifestation of antiphospholipid syndrome. Here, we present our experience with antiphospholipid syndrome secondary to systemic lupus erythematosus.

CASE PRESENTATION

A 10 year-old girl from a Hindu family in Sindh, Pakistan, who had previously been healthy, presented in 2020 with a 1-week history of abdominal pain, gross hematuria, vomiting, and fever. On examination, she was anxious, febrile, hypertensive, and had an enlarged, tender right kidney. Other systemic examinations, including skin, locomotor, respiratory, cardiovascular, and nervous systems, were unremarkable. Initial investigations for ureteric colic and acute pyelonephritis were negative, but revealed thrombocytopenia on complete blood count, mild proteinuria, hematuria on urinalysis, and normal kidney and liver function tests, along with normal prothrombin and activated partial thromboplastin times. An abdominal ultrasound showed a diffusely enlarged, echogenic right kidney with a loss of corticomedullary distinction and cortical hypoechoic areas, while the left kidney appeared normal. Color Doppler ultrasound identified a large thrombus in the right renal vein, completely obstructing its lumen and showing no blood flow. The thrombus extended into the inferior vena cava. Computed tomography angiography confirmed an organized thrombus completely blocking the right renal vein and extending into the infrahepatic portion of the inferior vena cava. No prothrombotic risk factors were identified during clinical evaluation, and thrombophilia screening was negative. However, lupus serology and antiphospholipid antibodies were positive, confirming a diagnosis of secondary antiphospholipid syndrome.

MANAGEMENT AND OUTCOME

The patient was treated with enoxaparin anticoagulation, later transitioned to warfarin sodium, and her hypertension was managed with captopril and amlodipine. She showed gradual improvement over 10-12 days and was discharged on anticoagulants, antihypertensive medications, antiplatelet agents, and hydroxychloroquine. A follow-up Doppler ultrasound revealed persistent blockage of the right renal vein by the thrombus, with no thrombus in the inferior vena cava. A dimercaptosuccinic acid scan indicated a nonfunctioning right kidney. While nephrectomy was recommended, her parents declined the procedure. Anticoagulation therapy was switched to rivaroxaban to avoid frequent international normalized ratio monitoring. Her captopril was replaced after control of blood pressure with losartan. Over the next 4 years, her follow-up was uneventful. She demonstrated normal growth, stable blood pressure (off antihypertensive), and normal kidney function without proteinuria. There were no lupus flares or thrombotic recurrences. Her most recent urinalysis was normal, with a serum creatinine level of 0.6 mg/dL and an estimated glomerular filtration rate > 170 mL/min/1.73 m2.

CONCLUSION

Isolated renal vein thrombosis is a rare presentation of antiphospholipid syndrome and poses a diagnostic challenge in the absence of preexisting prothrombotic risk factors. Early diagnosis and timely management are crucial to prevent organ damage. In this case, the patient retained a solitary functioning kidney. Long-term follow-up is essential to monitor for lupus flares, thrombus recurrence, hypertension, proteinuria, and progression to chronic kidney disease, as well as to ensure continued thromboprophylaxis.

Renal hypertrophy and hyperfiltration is enhanced in early acquired compared with a congenital solitary function kidney model in sheep

A congenital solitary functioning kidney (C-SFK) or an early acquired SFK (EA-SFK), due to childhood unilateral nephrectomy (UNX), increases the risk of hypertension and kidney disease early in life. Evidence suggests that children with an EA-SFK may have a higher risk of future kidney disease compared with those with a C-SFK, but the precise underlying mechanisms need further investigation. C-SFK was induced by fetal UNX at 100 days gestation (term=150 days) in male sheep fetuses, and a sham procedure was performed. At approximately one month of age, EA-SFK was induced by UNX in male lambs. At eight months of age, total kidney weight was similar in all groups due to marked hypertrophy in the C-SFK and EA-SFK groups. Blood pressure was similar in EA-SFK and sham groups but ~12 mmHg higher in the C-SFK group compared with sham. Compared with the sham group, glomerular filtration rate (GFR) was ~9% less in the EA-SFK group and ~26% less in the C-SFK. GFR was ~23% higher in EA-SFK compared with the C-SFK group. Albuminuria was ~67% higher in C-SFK sheep but similar in the EA-SFK group compared with sham sheep. However, like the C-SFK group, the renal blood flow response to nitric oxide blockade was attenuated in the EA-SFK group compared with sham. In conclusion, long-term studies are needed to determine whether the higher hyperfiltration and disturbed vasodilator balance observed in EA-SFK sheep will cause an accelerated decline in renal function with aging.

A Systematic Review for Guidelines: Sports and High-Grade Kidney Injuries in Children With Solitary Kidneys

AIM

To determine the risk of Grades IV and V kidney injury due to common children's sports.

METHODS

A systematic review of studies reporting traumatic kidney injuries (TKIs) associated with basketball, cycling, equestrian, motorsports, netball, rugby, Australian football or soccer. Studies with patients exclusively 18 years or older, non-TKIs or non-sport-related mechanisms were excluded.

RESULTS

Twenty-five studies with 24 424 patients were included. The estimated risk of kidney loss from sports injuries is 0.37 per million child-years. However, the incidence of Grades IV and V injuries could not be calculated in at-risk populations due to limited prospective data. The prevalence of TKIs from sport-specific trauma was low, ranging from 0.6% to 2.2%. Few studies graded the severity of kidney injury, but in the small number reported, Grades IV and V injuries occurred in 33% of soccer TKIs, 26% of bicycling, 23% of Australian football, 20% of basketball and 17% of equestrian injuries. The high number of ungraded kidney injuries (5514/5607) impacts the reliability of findings.

CONCLUSION

Recommendations to exclude children with congenital single kidneys from specific sports lack a firm evidence-base. Given bio-psycho-social consequences, such recommendations must be carefully considered, particularly for equestrian and motorised vehicles, which carry a higher risk of trauma.

The evaluation of kidney function estimation during lifestyle intervention in children with overweight and obesity

BACKGROUND

Children with overweight and obesity are at risk for developing chronic kidney disease (CKD). During lifestyle adjustment, the first step in the treatment of childhood obesity, body proportions are likely to change. The aim of this study was to examine how lifestyle intervention affects creatinine-based kidney function estimation in children with overweight and obesity.

METHODS

This longitudinal lifestyle intervention study included 614 children with overweight and obesity (mean age 12.17 ± 3.28 years, 53.6% female, mean BMI z-score 3.32 ± 0.75). Loss to follow-up was present: 305, 146, 70, 26, and 10 children were included after 1, 2, 3, 4, and 5 (about yearly) follow-up visits, respectively. Serum creatinine (SCr) was rescaled using Q-age and Q-height polynomials.

RESULTS

At baseline, 95-97% of the children had a SCr/Q-height and SCr/Q-age in the normal reference range [0.67-1.33]. SCr/Q significantly increased each (about yearly) follow-up visit, and linear mixed regression analyses demonstrated slopes between 0.01 and 0.04 (corresponding with eGFR FAS reduction of 1.1-4.1 mL/min/1.73 m2) per visit. BMI z-score reduced in both sexes and this reduction was significantly higher in males. No correlation between change in rescaled SCr and BMI z-score reduction could be demonstrated.

CONCLUSIONS

Rescaled serum creatinine (SCr/Q) slightly increases during multidiscipline lifestyle intervention in this cohort of children with overweight and obesity. This effect seems to be independent from change in BMI z-score. Whether this minor decrease in estimated kidney function has clinical consequences in the long term remains to be seen in trials with a longer follow-up period.

CLINICAL TRIAL REGISTRATION

ClinicalTrial.gov; Registration Number: NCT02091544.

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.

The rationale for nephron-sparing surgery in unilateral non-syndromic Wilms tumour

The central question of nephron-sparing surgery in unilateral non-syndromic Wilms tumour sits at a crossroads between surgery, oncology, and nephrology. There has been a significant paradigm shift in paediatric oncology towards reducing toxicity and addressing long-term treatment-related sequalae amongst childhood cancer survivors. After paediatric nephrectomy and 30-50 years of follow-up, 40% of patients will have chronic kidney disease, including 22% with hypertension and 23% with albuminuria. It is difficult to predict which patients will progress to develop hypertension, reduced glomerular filtration rate, albuminuria, and a higher cardiovascular risk. For these reasons, nephron-sparing surgery when it is technically feasible must be considered. To decrease the incidence of positive surgical margins (viable tumour present at a resection margin), incomplete lymph node sampling, and complications, these procedures should be performed at specialist and experienced reference centres. Based on the impacts of individual treatment pathways, survivors of childhood WT need to be followed through adulthood for early detection of chronic kidney disease, hypertension, and prevention of cardiovascular events.

Genetic and environmental factors driving congenital solitary functioning kidney

BACKGROUND

Congenital solitary functioning kidney (CSFK) is an anomaly predisposing to hypertension, albuminuria and chronic kidney disease. Its aetiology is complex and includes genetic and environmental factors. The role of gene-environment interactions (G×E), although relevant for other congenital anomalies, has not yet been investigated. Therefore, we performed a genome-wide G×E analysis with six preselected environmental factors to explore the role of these interactions in the aetiology of CSFK.

METHODS

In the AGORA (Aetiologic research into Genetic and Occupational/environmental Risk factors for Anomalies in children) data- and biobank, genome-wide single-nucleotide variant (SNV) data and questionnaire data on prenatal exposure to environmental risk factors were available for 381 CSFK patients and 598 healthy controls. Using a two-step strategy, we first selected independent significant SNVs associated with one of the six environmental risk factors. These SNVs were subsequently tested in G×E analyses using logistic regression models, with Bonferroni-corrected P-value thresholds based on the number of SNVs selected in step one.

RESULTS

In step one, 7-40 SNVs were selected per environmental factor, of which only rs3098698 reached statistical significance (P = .0016, Bonferroni-corrected threshold 0.0045) for interaction in step two. The interaction between maternal overweight and this SNV, which results in lower expression of the Arylsulfatase B (ARSB) gene, could be explained by lower insulin receptor activity in children heterozygous for rs3098698. Eight other G×E interactions had a P-value <.05, of which two were biologically plausible and warrant further study.

CONCLUSIONS

Interactions between genetic and environmental factors may contribute to the aetiology of CSFK. To better determine their role, large studies combining data on genetic and environmental risk factors are warranted.

Transitional Care for Patients with Congenital Colorectal Diseases: An EUPSA Network Office, ERNICA, and eUROGEN Joint Venture

BACKGROUND

Transition of care (TOC; from childhood into adulthood) of patients with anorectal malformations (ARM) and Hirschsprung disease (HD) ensures continuation of care for these patients. The aim of this international study was to assess the current status of TOC and adult care (AC) programs for patients with ARM and HD.

METHODS

A survey was developed by members of EUPSA, ERN eUROGEN, and ERNICA, including patient representatives (ePAGs), comprising of four domains: general information, general questions about transition to adulthood, and disease-specific questions regarding TOC and AC programs. Recruitment of centres was done by the ERNs and EUPSA, using mailing lists and social media accounts. Only descriptive statistics were reported.

RESULTS

In total, 82 centres from 21 different countries entered the survey. Approximately half of them were ERN network members. Seventy-two centres (87.8%) had a self-reported area of expertise for both ARM and HD. Specific TOC programs were installed in 44% of the centres and AC programs in 31% of these centres. When comparing centres, wide variation was observed in the content of the programs.

CONCLUSION

Despite the awareness of the importance of TOC and AC programs, these programs were installed in less than 50% of the participating centres. Various transition and AC programs were applied, with considerable heterogeneity in implementation, content and responsible caregivers involved. Sharing best practice examples and taking into account local and National Health Care Programs might lead to a better continuation of care in the future.

LEVEL OF EVIDENCE

III.

Congenital Anomalies of the Kidney and Urinary Tract: A Continuum of Care

Congenital anomalies of the kidney and urinary tract (CAKUT) are the leading cause of kidney failure in children and adolescents. CAKUT describes a wide spectrum of structural disorders with a prenatal origin. The etiology of CAKUT is multifactorial, including environmental, nongenetic, and genetic causes that impact kidney development as well as upper and lower urinary tract development. Adult nephrologists who treat patients with CAKUT may be challenged by the underlying diseases they are not familiar with and the accumulation of chronic kidney disease complications in childhood. This article discusses CAKUT etiology and presentation, the course during childhood and adolescence, as well as adult issues in CAKUT patients including CKD complications, urologic interventions, and genetic counseling. A smooth transition of CAKUT patients from pediatric to adult care can be challenging. Semin Nephrol 43:x-xx © 2023 Elsevier Inc. All rights reserved.

Predicting outcomes in children with congenital anomalies of the kidney and urinary tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most frequent causes of childhood chronic kidney disease (CKD). Using a large CAKUT cohort, we sought to identify the predictors of CKD and to develop a prediction model that informs a risk-stratified clinical pathway.

METHODS

This was a retrospective cohort study including cases with multicystic dysplastic kidneys (MCDK), unilateral kidney agenesis (UKA), kidney hypoplasia (KH), and posterior urethral valves (PUV). We identified risk factors for CKD (estimated glomerular filtration rate [eGFR] <60 ml/min/1.73 m2) and tested their performance in an adjusted multivariate binary regression model. Prediction probability scores for CKD were used to separate cases likely to develop complications from those not needing specialist follow-up.

RESULTS

We identified 452 eligible cases of CAKUT with 22% developing CKD. Strongest associations with CKD included primary diagnosis (OR 3.5, 95% CI 2.6-4.6), preterm delivery (OR 2.3, 95% CI 1.2-4.4), non-kidney anomalies (OR 1.8, 95% CI 1.1-3), first eGFR<90 (OR 8.9, 95% CI 4.4-18.1), small kidney size (OR 9, 95% CI 4.9-16.6), and additional kidney anomalies (OR 1.6, 95% CI 1.2-2.8). PUV (OR 4.7, 95% CI 1.5-15.3), first eGFR <90 (OR 4.4, 95% CI 2-9.7), and kidney length to body length ratio <7.9 (OR 4.2, 95% CI 1.9-9.2) were independent predictors of CKD. The regression model had a prediction accuracy of 80% and a prediction probability c-statistic of 0.81.

CONCLUSION

Using a large combined CAKUT cohort we identified risk factors for CKD. Our prediction model provides the first steps towards a risk-stratified clinical pathway. A higher resolution version of the Graphical abstract is available as Supplementary information.

GFR measurements and ultrasound findings in 154 children with a congenital solitary functioning kidney

BACKGROUND

Multicystic dysplastic kidney (MCDK) and unilateral renal agenesis (URA) are the most common reasons for a congenital solitary functioning kidney (SFK). We aimed to assess the presence of abnormalities in the congenital SFK and evaluate kidney function using chrome EDTA (CrEDTA) measurements.

METHODS

We retrospectively reviewed the medical records of 154 children with MCDK and URA in the period from 2005 to 2022 to analyze results from ultrasound scans and CrEDTA glomerular filtration rate (GFR) examinations.

RESULTS

Of 154 children with a solitary kidney due to MCDK (62%) or URA (38%), abnormalities on the congenital SFK were found in 13 children (8%). The abnormalities spontaneously resolved in 6 children (46%). The most common abnormality was hydronephrosis. Compensatory hypertrophy was found in 17% of the children within the first 6 months of life. 116 children (90%) had a standard GFR (sdGFR) above 75% of expected for the age. Out of those with a sdGFR below 75% of expected, 3 (23%) had abnormalities in the congenital SFK. There was no difference in sdGFR between children with MCDK and URA.

CONCLUSIONS

Our study is the first using CrEDTA for GFR measurements and suggests that most children with a congenital SFK due to MCDK or URA have a kidney function within expected for the age. Compensatory hypertrophy of the SFK is found in a minority of children within the first six months of life, suggesting that this process is developing over time. The prevalence of abnormalities in the SFK seems low, however those with abnormalities (e.g. hydronephrosis) are at higher risk of reduced sdGFR.

Brief early life angiotensin-converting enzyme inhibition attenuates the diuretic response to saline loading in sheep with solitary functioning kidney

A solitary functioning kidney (SFK) from birth predisposes to hypertension and kidney dysfunction, and this may be associated with impaired fluid and sodium homeostasis. Brief and early angiotensin-converting enzyme inhibition (ACEi) in a sheep model of SFK delays onset of kidney dysfunction. We hypothesized that modulation of the renin-angiotensin system via brief postnatal ACEi in SFK would reprogram renal sodium and water handling. Here, blood pressure (BP), kidney haemodynamics and kidney excretory function were examined in response to an isotonic saline load (0.13 ml/kg/min, 180 min) at 20 months of age in SFK (fetal unilateral nephrectomy at 100 days gestation; term 150 days), sham and SFK+ACEi sheep (ACEi in SFK 4-8 weeks of age). Basal BP was higher in SFK than sham (∼13 mmHg), and similar between SFK and SFK+ACEi groups. Saline loading caused a small increase in BP (∼3-4 mmHg) the first 2 h in SFK and sham sheep but not SFK+ACEi sheep. Glomerular filtration rate did not change in response to saline loading. Total sodium excretion was similar between groups. Total urine excretion was similar between SFK and sham animals but was ∼40% less in SFK+ACEi animals compared with SFK animals. In conclusion, the present study indicates that water homeostasis in response to a physiological challenge is attenuated at 20 months of age by brief early life ACEi in SFK. Further studies are required to determine if ACEi in early life in children with SFK could compromise fluid homeostasis later in life.

Youth with single kidneys-what is the evidence of risk?

Children and youth with a congenital or acquired single functioning kidney are at risk for development of kidney injury and chronic kidney disease. How best to use surrogate measures associated with risk factors poses many problems. The risk of progressive kidney disease for those with a single functioning kidney varies, and how to assess it remains imperfect. Developing better measures to determine the risk of chronic kidney disease-renal functional reserve and imaging that includes nephron number-may be within reach and would likely positively affect the outcome.

A Genome-Wide Association Study into the Aetiology of Congenital Solitary Functioning Kidney

Congenital solitary functioning kidney (CSFK) is a birth defect that occurs in 1:1500 children and predisposes them to kidney injury. Its aetiology is likely multifactorial. In addition to known monogenic causes and environmental risk factors, common genetic variation may contribute to susceptibility to CSFK. We performed a genome-wide association study among 452 patients with CSFK and two control groups of 669 healthy children and 5363 unaffected adults. Variants in two loci reached the genome-wide significance threshold of 5 × 10-8, and variants in 30 loci reached the suggestive significance threshold of 1 × 10-5. Of these, an identified locus with lead single nucleotide variant (SNV) rs140804918 (odds ratio 3.1, p-value = 1.4 × 10-8) on chromosome 7 was most promising due to its close proximity to HGF, a gene known to be involved in kidney development. Based on their known molecular functions, both KCTD20 and STK38 could explain the suggestive significant association with lead SNV rs148413365 on chromosome 6. Our findings need replication in an independent cohort of CSFK patients before they can be established definitively. However, our analysis suggests that common variants play a role in CSFK aetiology. Future research could enhance our understanding of the molecular mechanisms involved.