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[Age dependence of kidney function]
A Steinsträsser1, R Berberich, H Wilhelm
1Abteilung für Nuklearmedizin Radiologischen Universitätsklinik, Hamburg/Saar.
Insights
Kidney clearance does not differ by sex. Maximal kidney clearance occurs around age 8, with the most variability in infants under 2 years. Age-based correction factors can be derived for clinical use.
Area of Science:
- Nephrology
- Pediatric Nephrology
- Pharmacokinetics
Context:
- Kidney function assessment often uses body surface area for correction, but age adjustments are less common despite immature infant kidney function and age-related decline in adults.
- Previous studies on age and kidney clearance yielded inconsistent results, likely due to small sample sizes.
Purpose:
- To establish a statistically significant relationship between age and kidney clearance using a large dataset.
- To develop age-based correction factors for kidney clearance to enable comparison with a standard reference value.
Summary:
- Analyzed over 1000 studies, categorizing participants into infants (<2 years), children/adolescents (2-15 years), and adults (16-80 years).
- Found no significant differences in kidney clearance between sexes.
- Maximal kidney clearance was observed around age 8, with the highest variability in children under 2 years, highlighting a discrepancy between maturation and calendar age.
- Developed a continuous three-trunk function to describe kidney clearance across ages, enabling the derivation of age-specific correction factors.
Impact:
- Provides a robust, age-dependent model for kidney clearance, improving accuracy in pediatric and adult populations.
- Facilitates standardized comparison of individual kidney clearance values to a normal reference, aiding clinical diagnosis and drug dosing.
- Highlights the importance of age-specific considerations in kidney function assessment, particularly in early childhood.
Abstract:
Although kidney function is immature in infants and decreases with increasing age in adults, when assessing the kidney clearance, it is not common to make an adjustment for age. On the other hand, correction for the standard body surface is generally accepted. Previous studies have yielded contradictory results, probably due to the small numbers of patients studied. To obtain the statistically significant relationship between age and kidney clearance, we compiled more than 1000 studies. These studies were divided into three groups: (1) children under 2 years of age (n = 71); (2) children and adolescents from 2 to 15 years (n = 64 male/58 female); (3) adults (n = 474 male/424 female; age: 16-80 years). Total clearance determinations were only considered if there were no differences between the two kidneys and if there was no obstruction of micturition or other pathological findings. Surprisingly, the statistical analysis showed no differences in clearance values between sexes. The maximal clearance values were found in the groups with children about 8 years old and the greatest scatter of values was seen in children under 2 years of age (a discrepancy between maturation age and calendar age). The complete set of data was based on the presumption that continuous function consisting of three trunks describes the course of normal kidney clearance in relation to patient age. If one determines an arbitrary reference value (e.g., 25 years), correction factors can easily be derived from the function described in order to compare individual clearance with a normal value.(ABSTRACT TRUNCATED AT 250 WORDS)