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How should renal hemodynamic data be indexed in obesity?
R E Schmieder1, A H Beil, H Weihprecht
1Department of Internal Medicine-Nephrology, University of Erlangen-Nümberg, Germany.
Journal of the American Society of Nephrology : JASN
|March 1, 1995
Summary
Standard renal perfusion (RPF) indexing to body surface area is inaccurate for obese individuals. RPF correlates with height, not surface area, in obese subjects, necessitating a revised clinical approach.
Area of Science:
- Nephrology
- Physiology
- Medical Imaging
Background:
- Renal perfusion (RPF) is typically normalized to a standard body surface area (BSA) of 1.73 m².
- The accuracy of this normalization method for obese individuals is questionable.
Purpose of the Study:
- To investigate whether indexing RPF to BSA accurately reflects renal perfusion in obese subjects.
- To determine the optimal method for normalizing RPF in individuals with varying body weights.
Main Methods:
- Measured RPF using (131I)para-aminohippuric acid clearance in 215 subjects with diverse characteristics.
- Employed multiple regression analysis to identify predictors of RPF, including age, height, weight, body mass index, and mean arterial blood pressure.
- Compared RPF values normalized to BSA and height across different weight categories (normal, overweight, severely overweight).
Main Results:
- Multiple regression analysis identified age, height, and arterial blood pressure as independent predictors of RPF, while weight and BMI were not significant.
- RPF indexed to BSA showed a significant decline with increasing obesity.
- RPF indexed to height demonstrated no significant difference across weight categories, aligning with regression analysis findings.
Conclusions:
- Obesity is not a determinant of RPF.
- Indexing RPF to BSA results in underestimated values for obese patients.
- RPF values in obese subjects correlate with height, not body surface area, suggesting a need to revise current normalization practices.