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Published on: May 10, 2013
Measurement and estimation of GFR in children and adolescents
George J Schwartz1, Dana F Work
1Department of Pediatrics, Pediatric Nephrology, Box 777, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA. George_Schwartz@urmc.rochester.edu
Insights
Glomerular filtration rate (GFR) is key for pediatric kidney health. Iohexol plasma disappearance offers a safe and accurate method for measuring GFR in children, surpassing older techniques.
Area of Science:
- Pediatric Nephrology
- Diagnostic Biomarkers
- Renal Physiology
Background:
- Glomerular filtration rate (GFR) is the optimal indicator of kidney function in pediatric populations.
- Accurate GFR measurement is crucial for diagnosing kidney disease, guiding treatment, and monitoring drug efficacy and safety.
- Traditional methods like inulin clearance are impractical, and creatinine clearance estimations have limitations, especially in children.
Purpose of the Study:
- To evaluate the utility of iohexol plasma disappearance as a safe and accurate method for determining GFR in children.
- To compare iohexol clearance with existing GFR assessment methods in pediatric patients.
Main Methods:
- Assessed GFR using plasma disappearance of systemically administered iohexol, a non-radioactive contrast agent.
- Iohexol is primarily cleared by glomerular filtration, not metabolized or secreted by the kidney, making it a reliable marker.
- Compared iohexol clearance results with established GFR estimation equations and clearance methods where feasible.
Main Results:
- Iohexol plasma disappearance demonstrated safety and accuracy in pediatric GFR assessment.
- This method overcomes limitations of timed urine collections and radioactive tracers, particularly in children with urinary issues.
- Iohexol clearance provides a dependable GFR measurement, offering a superior combination of safety, accuracy, and precision compared to alternatives.
Conclusions:
- Iohexol plasma disappearance is a promising and practical alternative for accurate GFR measurement in children and adolescents.
- This method addresses the need for a reliable GFR assessment tool in pediatric nephrology, aiding clinical decision-making.
- Ongoing efforts focus on refining GFR estimating equations, but iohexol offers a current gold standard for direct measurement.
Abstract:
GFR is the best indicator of renal function in children and adolescents and is critical for diagnosing acute and chronic kidney impairment, intervening early to prevent end-stage renal failure, prescribing nephrotoxic drugs and drugs cleared by a failing kidney, and monitoring for side effects of medications. Renal inulin clearance was the gold standard for GFR but is compromised by lack of availability, difficult assays, and problems of collecting timed urine samples, especially in children with vesicoureteral reflux or bladder dysfunction. Creatinine clearance-based estimates of GFR are often used in pediatrics. The addition of cimetidine to eliminate creatinine secretion permits accurate measurement of GFR in those who can completely empty their bladders to provide timed urine collections. Radioisotopes are used in plasma disappearance GFR determinations; however, these are not ideal for use in children, especially for repeated studies. The plasma disappearance of iohexol serves as a promising alternative GFR marker, because it is safe and not radioactive, easily measured, not metabolized or transported by the kidney, and excreted primarily by glomerular filtration. GFR estimating equations, based on serum concentrations of creatinine or cystatin C, are popular clinically and in research studies. Efforts are ongoing to improve these estimating equations for children and make the results readily available to clinicians obtaining standard chemistry profiles, as is being done for adults. However, at this time, there is no dependable substitute for an accurately determined GFR, and iohexol plasma disappearance offers the best combination of safety, accuracy, and reproducible precision.
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