Kidney function in severely obese adolescents undergoing bariatric surgery

Understanding the Current Landscape of Kidney Disease in Canada to Advance Precision Medicine Guided Personalized Care

Purpose of Review

To understand the impact of kidney disease in Canada and the priority areas of kidney research that can benefit from patient-oriented, precision medicine research using novel technologies.

Sources of Information

Information was collected through discussions between health care professionals, researchers, and patient partners. Literature was compiled using search engines (PubMed, PubMed central, Medline, and Google) and data from the Canadian Organ Replacement Register.

Methods

We reviewed the impact, prevalence, economic burden, causes of kidney disease, and priority research areas in Canada. After reviewing the priority areas for kidney research, potential avenues for future research that can integrate precision medicine initiatives for patient-oriented research were outlined.

Key Findings

Chronic kidney disease (CKD) remains among the top causes of morbidity and mortality in the world and exerts a large financial strain on the health care system. Despite the increasing number of people with CKD, funding for basic kidney research continues to trail behind other diseases. Current funding strategies favor existing clinical treatment and patient educational strategies. The identification of genetic factors for various forms of kidney disease in the adult and pediatric populations provides mechanistic insight into disease pathogenesis. Allocation of resources and funding toward existing high-yield personalized research initiatives have the potential to significantly affect patient-oriented research outcomes but will be difficult due to a constant decline of funding for kidney research.

Limitations

This is an overview primarily focused on Canadian-specific literature rather than a comprehensive systematic review of the literature. The scope of our findings and conclusions may not be applicable to health care systems in other countries.

Tangled relationship between insulin resistance and microalbuminuria in children with obesity

Childhood obesity represents a complex disease with a well-known cardiometabolic burden including fatty liver, type 2 diabetes, metabolic syndrome, and cardiovascular disease. From a pathogenic point of view, insulin resistance (IR) represents the key factor underlying the spectrum of these obesity consequences. As observed in adults, recent data supported the occurrence of microalbuminuria (MA) as marker of early kidney dysfunction and its potential link with cardiometabolic factors also in children with obesity. In fact, a well-documented pathophysiological hypothesis both in adults and children supported an intimate correlation with the major feature of obesity such as IR through the influence of insulin on renal hemodynamics. Based on the clinical and prognostic relevance of this relationship in daily practice (including an increased risk of chronic kidney disease development overtime), more scientific attention needs to be paid to the evaluation of early kidney damage in children with obesity. In this paper, we attempt to address three debated questions regarding the intriguing liaison between IR and MA in children with obesity: (1) What is the prevalence of pediatric MA? (2) What is the state of art of MA in children with obesity? and (3) Is there a link between IR and MA in children with obesity?

The Effect and Prevalence of Comorbidities in Adolescents With CKD and Obesity

Adolescent obesity and CKD are both significant public health issues independently. When seen as comorbid conditions, they can cause deleterious health outcomes that put them on the fast track to necessitate dialysis or transplantation. This paper analyzes the effects of various biomarkers and comorbidities seen in the intersection of obesity and CKD in the adolescent population. We illustrate the estimated prevalence of these biomarkers and comorbidities through a review of the literature, available treatment, and obesity-related glomerulopathies. We found significant prevalence of the biomarkers, microalbuminuria (9.42% ± 9.31% and interquartile range [IQR] of 9.5%), hypertension (23.60% ± 22.5% and IQR of 9.5%), low high-density lipoprotein (14.34% ± 5.46% and IQR of 5%), hyperfiltration (3.12% ± 5.16% and IQR of 4%), and lower estimated glomerular filtration rate 4.59 ± 2.75 and IQR of 3%. Identification of prevalent biomarkers and their manifestations can serve to inform clinicians what to look for in daily setting and help elucidate the magnitude of this growing issue. Additionally, pertinent treatment options from pharmacotherapy to bariatric surgery are outlined to provide care providers with the full spectrum of treatment options for obesity in adolescent populations.

Impact of Obesity in Kidney Diseases

The clinical consequences of obesity on the kidneys, with or without metabolic abnormalities, involve both renal function and structures. The mechanisms linking obesity and renal damage are well understood, including several effector mechanisms with interconnected pathways. Higher prevalence of urinary albumin excretion, sub-nephrotic syndrome, nephrolithiasis, increased risk of developing CKD, and progression to ESKD have been identified as being associated with obesity and having a relevant clinical impact. Moreover, renal replacement therapy and kidney transplantation are also influenced by obesity. Losing weight is key in limiting the impact that obesity produces on the kidneys by reducing albuminuria/proteinuria, declining rate of eGFR deterioration, delaying the development of CKD and ESKD, and improving the outcome of a renal transplant. Weight reduction may also contribute to appropriate control of cardiometabolic risk factors such as hypertension, metabolic syndrome, diabetes, and dyslipidemia which may be protective not only in renal damage but also cardiovascular disease. Lifestyle changes, some drugs, and bariatric surgery have demonstrated the benefits.

Obesity Facts and Their Influence on Renal Function Across the Life Span

Obesity is a chronic disease, with a rapidly increasing prevalence worldwide. Body mass index (BMI) provides the most useful population-level measure of overweight and obesity. For adults, overweight is defined as a BMI (Kg/m²) ≥ 25, and obesity as a BMI ≥ 30, for non-Asians and ≥ 27.5 for Asians. Abdominal obesity can be defined as a waist circumference equal to or higher than 102 cm for men and ≥88 cm for women. The definition of children and adolescents BMI changes with age and sex. Obesity may be exogenous or endogenous obesity, the latter is multifactorial and predominantly manifested during childhood. Presently, overweight and obesity are linked to more deaths worldwide than underweight. The total kidney glomerular filtration rate (GFR) is determined by the sum of nephrons and the GFR within each nephron or single nephron GFR. In clinical practice, GFR is more frequently calculated by GFR estimating equations based upon the plasma levels of creatinine, cystatin C, or both. The measured value of plasma creatinine is strongly influenced by non-GFR factors, by its tubular and gastrointestinal secretion, and by the problems associated with the lack of standardization of creatinine's laboratory assay discrediting it as an ideal GFR biomarker. Unlike creatinine, cystatin C plasma levels are mainly determined by GFR. Obesity may affect the kidney, via development of systemic arterial hypertension and/or diabetes mellitus, or directly, by ectopic accumulation of adipose tissue in the kidney. As obesity is a clinical condition associated with altered body composition, creatinine may not be the ideal biomarker for GFR measurement in obese individuals.

Safe Use of Opioids in Chronic Kidney Disease and Hemodialysis Patients: Tips and Tricks for Non-Pain Specialists

In patients suffering from moderate-to-severe chronic kidney disease (CKD) or end-stage renal disease (ESRD), subjected to hemodialysis (HD), pain is very common, but often underestimated. Opioids are still the mainstay of severe chronic pain management; however, their prescription in CKD and HD patients is still significantly low and pain is often under-treated. Altered pharmacokinetics and the lack of clinical trials on the use of opioids in patients with renal impairment increase physicians' concerns in this specific population. This narrative review focused on the correct and safe use of opioids in patients with CKD and HD. Morphine and codeine are not recommended, because the accumulation of their metabolites may cause neurotoxic symptoms. Oxycodone and hydromorphone can be safely used, but adequate dosage adjustments are required in CKD. In dialyzed patients, these opioids should be considered as second-line agents and patients should be carefully monitored. According to different studies, buprenorphine and fentanyl could be considered first-line opioids in the management of pain in CKD; however, fentanyl is not appropriate in patients undergoing HD. Tapentadol does not need dosage adjustment in mild-to-moderate renal impairment conditions; however, no data are available on its use in ESRD. Opioid-related side effects may be exacerbated by common comorbidities in CKD patients. Opioid-induced constipation can be managed with peripherally-acting-μ-opioid-receptor-antagonists (PAMORA). Unlike the other PAMORA, naldemedine does not require any dose adjustment in CKD and HD patients. Accurate pain diagnosis, opioid titration and tailoring are mandatory to minimize the risks and to improve the outcome of the analgesic therapy.

Five-year kidney outcomes of bariatric surgery differ in severely obese adolescents and adults with and without type 2 diabetes

Bariatric surgery improves markers of kidney health in severe obesity, yet it is unclear if kidney disease outcomes differ according to age at surgery. Therefore, we examined health effects of Roux-en-Y gastric bypass between 161 adolescents and 396 adults participating in two related but distinct studies. Primary outcomes were elevated urine albumin-to-creatinine ratio (UACR) of 30 mg/g or more and hyperfiltration (an estimated glomerular filtration rate of 135 ml/min/1.73m² or more). Analyses were stratified by the presence of pre-operative type 2 diabetes. Adolescents with pre-operative type 2 diabetes had a significantly increased prevalence of elevated UACR prior to surgery compared to adults (22.5 vs. 9.0%). Resolution of elevated UACR following surgery differed between adolescents and adults with type 2 diabetes, with adolescents experiencing a significantly earlier improvement following surgery. Adolescents without pre-operative type 2 diabetes demonstrated a significantly increased prevalence of UACR prior to surgery compared to adults (9.4 vs. 4.5%), with no improvement occurring in either group post-operatively. Adolescents with pre-operative type 2 diabetes had a significantly increased prevalence of hyperfiltration that remained throughout the study period, whereas hyperfiltration prevalence was similar among those without type 2 diabetes. Thus, adolescents with pre-operative type 2 diabetes experienced earlier attenuation of elevated UACR compared to adults with pre-operative type 2 diabetes in response to gastric bypass.

Bariatric surgery and kidney disease outcomes in severely obese youth

Bariatric surgery, an emerging treatment for severely obese youth with and without T2D, provides marked improvement in insulin resistance, beta-cell function, and central adiposity. Further, preliminary data suggest that bariatric surgery also results in significant improvement in markers of obesity-related nephropathy and DKD, beyond that which can be achieved with current medical interventions. Yet, the mechanisms whereby bariatric surgery attenuates kidney disease remain unclear. This review summarizes the data on the effects of bariatric surgery on obesity-related nephropathy and DKD in youth with and without T2D, in addition to potential mechanisms underlying the nephroprotective effects of weight loss surgery and how these may differ in Roux-en-Y gastric bypass vs. vertical sleeve gastrectomy. Finally, we discuss potential future non-surgical therapies to mitigate kidney disease.

Modern pharmacological treatment of obese patients

There are many angles to consider in drug treatment of obese patients. On the one hand, some specific weight loss drugs are available, on the other, several drugs are associated with unintentional weight changes. When treating an obese patient for any given disease, several physiological changes may influence the pharmacokinetic properties of the drugs required. Thus, increased body weight may influence the efficacy and safety of some drug treatments. Even more complicated is the situation after weight reduction surgery. Due to the various changes to the gastrointestinal tract induced by the different surgical techniques used, and the dynamic changes in body composition thereafter, drug dosing has to be constantly reconsidered. Whereas all of these issues are of clinical importance, none of them have been investigated in the necessary depth and broadness to ensure safe and efficacious drug treatment of the massively obese patient. Individual considerations have to be based on comorbidities, concomitant medication, and on specific drug properties, for example, lipophilicity, volume of distribution, and metabolism. In this article we summarize the data available on different aspects of drug treatment in the obese patient with the hope of improving patient care.

Can childhood obesity influence later chronic kidney disease?

Childhood overweight and obesity affects more and more children. Whilst associations of childhood overweight with later outcomes such as hypertension, diabetes and cardiovascular disease have been well documented, less is known about the association of childhood overweight and obesity with kidney disease. We review the existing evidence for the association of childhood obesity with markers of childhood and adult kidney disease. Whilst there is some evidence for an association, studies have not been able to distinguish between childhood being a sensitive time to develop later kidney problems, or whether observed associations of childhood obesity with poor outcomes are driven by greater lifelong exposure to obesity.

Childhood Obesity and the Metabolic Syndrome

Obesity is a leading cause of chronic kidney disease. Children with severe obesity have an increased prevalence of early kidney abnormalities and are at high risk to develop kidney failure in adulthood. The pathophysiology of obesity-related kidney disease is incompletely understood, although the postulated mechanisms of kidney injury include hyperfiltration, adipokine dysregulation, and lipotoxic injury. An improved understanding of the long-term effects of obesity on kidney health is essential treat the growing epidemic of obesity-related kidney disease. The purpose of this article is to review the epidemiology, pathophysiology, clinical features, and management of obesity-related kidney disease in children and adolescents.

Frequency and Risk Factors of Kidney Alterations in Children and Adolescents who Are Overweight and Obese in a Primary Health-care Setting

OBJECTIVE

Obesity is clearly associated to kidney disease in adult population; however, there is scarce evidence in children and adolescents. The aim was to compare frequency of renal damage according to the presence of overweight-obesity in children and adolescents, as well as to compare nutritional and biochemical risk factors, according to the presence of kidney alterations.

METHODS

Cross-sectional study; 172 children and adolescents, 6-16 years old, without malnutrition, diabetes mellitus, hypertension and independent comorbid conditions associated to obesity or kidney disease, as well as transitory causes of microalbuminuria (MA) from a Primary Health-Care Unit were included. Clinical, biochemical, anthropometric and dietetic evaluations were measured in all subjects; subsequently they were classified as normal weight, overweight and obesity groups according to sex- and age-adjusted body mass index (BMI). Glomerular filtration rate (GFR, estimated by Schwartz equation) and albuminuria (albumin/creatinine ratio) were determined. Presence of kidney alterations was measured as decreased GFR (<90 mL/min/1.73m²), hyperfiltration (>170 mL/min/1.73m²) and MA (30-300 mg/g).

RESULTS

Compared with controls, subjects with overweight-obesity had significantly (P<.05) abdominal obesity (0 vs 69%), hypertension (19 vs 26%), hypertriglyceridemia (11 vs 47%), high low-density lipoprotein cholesterol (2 vs 8%) and low high-density lipoprotein cholesterol (HDL-cholesterol; 2 vs 28%), hyperuricemia (11 vs 28%) and hyperinsulinemia (8 vs 70%). Hyperfiltration and MA were present in 5 and 4 subjects with overweight/obesity, respectively, whereas decreased GFR was present in only 1 subject with obesity. Normal weight subjects had no kidney alterations. In multivariate analysis, kidney alterations were significantly predicted by higher BMI and lower HDL-cholesterol.

CONCLUSIONS

Kidney alterations were observed only in subjects with overweight (3.6%) and obesity (9.9%), who additionally, displayed cardiometabolic and kidney disease risk factors more frequently than normal weight subjects.

Improving kidney disease in obese adolescents: a surgical approach

Obesity has been associated with chronic kidney disease in adult studies, but little data exist in pediatrics. Nehus et al. offer the first study to show that bariatric surgery in severely obese adolescents is associated with improved renal outcomes. Despite limitations, this study provided compelling evidence that aggressive weight loss intervention can improve renal outcomes in young, severely obese subjects. Further investigation is required to determine mechanisms by which this may occur.

Obesity and chronic kidney disease

PURPOSE OF REVIEW

To review recent advances in the epidemiology, pathophysiology, clinical features, and treatment of obesity-related kidney disease.

RECENT FINDINGS

Studies have confirmed that obesity is associated with increased risk of developing chronic kidney disease (CKD). This risk extends to those who are metabolically healthy, indicating that obesity per se contributes to CKD independent of the metabolic syndrome. Recent developments in the pathophysiology of obesity-related kidney disease indicate that chronic inflammation and abnormal lipid metabolism contribute to kidney cell injury. Children with severe obesity have increased prevalence of early kidney abnormalities, including albuminuria, decreased kidney function, and elevated biomarkers of early kidney injury. For these patients, bariatric surgery has emerged as a treatment option to consider. Longitudinal studies in children and adults have demonstrated that in patients with obesity-related kidney disease, kidney function and albuminuria improve following bariatric surgery.

SUMMARY

The injurious renal effects of obesity are present in childhood, although the natural history and clinical spectrum of obesity-related kidney disease in children are not known. In obese children with early kidney disease, identification of kidney injury, implementation of preventive strategies, and prompt treatment are essential to improving clinical outcomes.

Evidence Base for Multidisciplinary Care of Pediatric/Adolescent Bariatric Surgery Patients

PURPOSE OF REVIEW

Severe childhood obesity, defined as having a body mass index (BMI) greater than the 99th percentile for age and gender, is rising in most countries and is associated with early morbidity and mortality. Optimal management of the health of the child with obesity requires a multidisciplinary approach that identifies and treats associated derangements.

RECENT FINDINGS

Lifestyle interventions such as diet, exercise, and behavioral therapy for the severely obese pediatric patient are generally not effective. Few centers worldwide offer bariatric surgery for adolescents in a multidisciplinary setting, and we are the only center that offers a multidisciplinary approach that incorporates bariatric surgery for severely obese children and adolescents across all age groups. In this paper, we review up-to-date evidence in this subject including ours, and provide details on the multidisciplinary approach to pediatric obesity that accommodates bariatric surgery for children across all age groups.

What Is the Evidence for Paediatric/Adolescent Bariatric Surgery?

PURPOSE OF REVIEW

In spite of the increasing prevalence of severe and complex obesity in children, surgery as a potential management option is still not widely accepted. The purpose of this review is to examine the evidence for surgical options in the severely obese paediatric population. Increasing evidence supports early rather than later use of bariatric surgery in the treatment of extreme obesity.

RECENT FINDINGS

Prior to 2007, the feasibility and safety of surgery have been reported by predominantly small, sporadic single-centre retrospective case series. Increasing long-term data is now emerging due to the formation of multi-centre prospective national consortiums with two large, prospective long-term outcome studies published within the last year aiding our understanding of the efficacy and safety of bariatric surgery within the adolescent population. It is increasingly clear that adolescent bariatric surgery outcomes are comparable to adults, with similar sustainable weight loss, resolution of co-morbidities and complication rates. However, these studies are solely from dedicated specialist adolescent centres and results may not be reproducible if not performed in regulated environments with specialist multi-disciplinary teams.

Kidney outcomes three years after bariatric surgery in severely obese adolescents

A significant number of severely obese adolescents undergoing bariatric surgery have evidence of early kidney damage. To determine if kidney injury is reversible following bariatric surgery, we investigated renal outcomes in the Teen-Longitudinal Assessment of Bariatric Surgery cohort, a prospective multicenter study of 242 severely obese adolescents undergoing bariatric surgery. Primary outcomes of urine albumin-to-creatinine ratio and cystatin C-based estimated glomerular filtration rate (eGFR) were evaluated preoperatively and up to 3 years following bariatric surgery. At surgery, mean age of participants was 17 years and median body mass index (BMI) was 51 kg/m². In those with decreased kidney function at baseline (eGFR under 90 mL/min/1.73m²), mean eGFR significantly improved from 76 to 102 mL/min/1.73m² at three-year follow-up. Similarly, participants with albuminuria (albumin-to-creatinine ratio of 30 mg/g and more) at baseline demonstrated significant improvement following surgery: geometric mean of ACR was 74 mg/g at baseline and decreased to 17 mg/g at three years. Those with normal renal function and no albuminuria at baseline remained stable throughout the study period. Among individuals with a BMI of 40 kg/m² and more at follow-up, increased BMI was associated with significantly lower eGFR, while no association was observed in those with a BMI under 40 kg/m². In adjusted analysis, eGFR increased by 3.9 mL/min/1.73m² for each 10-unit loss of BMI. Early kidney abnormalities improved following bariatric surgery in adolescents with evidence of preoperative kidney disease. Thus, kidney disease should be considered as a selection criteria for bariatric surgery in severely obese adolescents who fail conventional weight management.

The Impact of Nonalcoholic Fatty Liver Disease on Renal Function in Children with Overweight/Obesity

The association between nonalcoholic fatty liver disease (NAFLD) and chronic kidney disease has attracted interest and attention over recent years. However, no data are available in children. We determined whether children with NAFLD show signs of renal functional alterations, as determined by estimated glomerular filtration rate (eGFR) and urinary albumin excretion. We studied 596 children with overweight/obesity, 268 with NAFLD (hepatic fat fraction ≥5% on magnetic resonance imaging) and 328 without NAFLD, and 130 healthy normal-weight controls. Decreased GFR was defined as eGFR < 90 mL/min/1.73 m². Abnormal albuminuria was defined as urinary excretion of ≥30 mg/24 h of albumin. A greater prevalence of eGFR < 90 mL/min/1.73 m² was observed in patients with NAFLD compared to those without liver involvement and healthy subjects (17.5% vs. 6.7% vs. 0.77%; p < 0.0001). The proportion of children with abnormal albuminuria was also higher in the NAFLD group compared to those without NAFLD, and controls (9.3% vs. 4.0% vs. 0; p < 0.0001). Multivariate logistic regression analysis revealed that NAFLD was associated with decreased eGFR and/or microalbuminuria (odds ratio, 2.54 (confidence interval, 1.16–5.57); p < 0.05) independently of anthropometric and clinical variables. Children with NAFLD are at risk for early renal dysfunction. Recognition of this abnormality in the young may help to prevent the ongoing development of the disease.

Association of Microalbuminuria with Metabolic Syndrome among Aged Population

Background. The impact of the various components of metabolic syndrome (MetS) on chronic kidney disease has been conflicting. We aim to investigate the association between MetS and microalbuminuria and identify the major contributing components of MetS that result in microalbuminuria in the Chinese aged population. Methods. A total of 674 adults aged 55–98 years (males: 266; mean age: 66.5 ± 7.5 years) were studied. MetS was defined by the 2004 Chinese Diabetes Society criteria and microalbuminuria by urine albumin-creatinine ratio (UACR) ≥3 mg/mmoL. Results. The prevalence of microalbuminuria was gradually increased with increasing number of MetS components (P < 0.05). In multivariate regression, after adjusting for age and sex, MetS was the strongest correlate of microalbuminuria (OR = 1.781, 95% CI = 1.226–2.587; P < 0.05) followed by the fasting plasma glucose (FPG) (OR = 1.217, 95% CI = 1.044–1.092; P < 0.05), systolic blood pressure (SBP) (OR = 1.011, 95% CI = 1.107–1.338; P < 0.05), and high-density lipoprotein cholesterol (HDL-C) (OR = 0.576, 95% CI = 0.348–0.953; P < 0.05). Conclusions. MetS is independently associated with microalbuminuria in the Chinese aged population. Elevated FPG is the most predominant component of metabolic syndrome associated with microalbuminuria followed by elevated SBP and reduced HDL-C.

The kidney in obesity

Body mass index has been found to be the second most important contributor to relative risk for developing end state renal disease (ESRD), after proteinuria. The impact of obesity on the kidney includes a wide spectrum, from characteristic pathologic lesions to increment in urinary albumin excretion (UAE) and proteinuria/or decrease in glomerular filtration rate (GFR). The cause of renal disease associated to obesity is not well understood, but two relevant elements emerge. The first is the presence of obesity-related glomerulopathy, and the second is the fat deposit in the kidney with impact on renal haemodynamics and intrarenal regulation. The mechanisms linking obesity and renal damage are complex and include haemodynamic changes, inflammation, oxidative stress, apoptosis, and finally renal scarring. The protection of kidney damage needs to combine weight reduction with the proper control of the cardiometabolic risk factors associated, hypertension, metabolic syndrome, diabetes and dyslipidaemia. The search for specific treatments merits future research.

Cefoxitin Plasma and Subcutaneous Adipose Tissue Concentration in Patients Undergoing Sleeve Gastrectomy

PURPOSE

Antibiotic dosing in obese surgical patients has not been adequately evaluated. The objective of this study was to identify whether currently prescribed doses of cefoxitin achieve adequate and sustained plasma and tissue concentrations in obese patients undergoing sleeve gastrectomy.

METHODS

A prospective evaluation of plasma and tissue cefoxitin concentrations in patients undergoing sleeve gastrectomy was performed. On the day of the surgical procedure, venous blood samples (5 mL) were collected just before cefoxitin administration and then at 5, 30, 60, 120, and 240 minutes after dose administration. In addition, subcutaneous adipose tissue was collected from the surgical site at the time of surgical incision and at closure. Cefoxitin concentrations in the collected samples were quantified by using an HPLC-ultraviolet method. A standard noncompartmental analysis was performed for each individual cefoxitin plasma concentration-time profile. In addition, the ratio of tissue to plasma concentration was calculated for all patients.

FINDINGS

Plasma and tissue pharmacokinetics of cefoxitin were evaluated in 6 patients undergoing sleeve gastrectomy. The mean age and BMI were 48.7 (6.2) years and 42.8 (7.1) kg/m(2), respectively. At the time of surgical closure, subcutaneous adipose tissue concentrations of cefoxitin were subtherapeutic (<8 µg/mL) in all evaluated patients.

IMPLICATIONS

Current dosing strategies for cefoxitin in obese surgical patients may be inadequate, and there is an urgent need to define the appropriate dosage.

Subclinical kidney injury before and 1 year after bariatric surgery among adolescents with severe obesity

OBJECTIVE

To assess subclinical kidney injury in adolescents with severe obesity by measuring biomarkers of early kidney disease and to assess changes in the levels of these biomarkers following bariatric procedures.

METHODS

Twenty-two adolescents undergoing bariatric surgery with no microalbuminuria and normal kidney function were selected. Urinary NGAL, IL-18, and KIM-1 were measured at baseline, 6 and 12 months postoperatively. Biomarker levels were compared to 44 age-gender-matched lean controls.

RESULTS

Subjects with obesity had a mean baseline BMI of 48 kg/m(2) that decreased by 34% at 1-year follow-up. Urine NGAL, IL-18, and KIM-1 were significantly elevated in subjects with obesity compared to lean controls at baseline. The obese cohort had a further significant increase in NGAL and KIM-1 at 6 months, followed by decline at 1 year. The overall change in levels of all three biomarkers through 1 year after surgery, however, was not significant compared to baseline.

CONCLUSIONS

Adolescent severe obesity is associated with increased urinary excretion of novel biomarkers of kidney injury, despite no microalbuminuria or decreased kidney function. This subclinical kidney injury persists 1 year after significant weight loss induced by bariatric surgery, suggesting that close, long-term follow-up of kidney status is warranted in these adolescents.