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Single‐Nephron Glomerular Filtration Rate in Healthy Adults

BACKGROUND The glomerular filtration rate (GFR) assesses the function of all nephrons, and the single‐nephron GFR assesses the function of individual nephrons. How the single‐nephron GFR relates to demographic and clinical characteristics and kidney‐biopsy findings in humans is unknown. METHODS We identified 1388 living kidney donors at the Mayo Clinic and the Cleveland Clinic who underwent a computed tomographic (CT) scan of the kidney with the use of contrast material and an iothalamate‐based measurement of the GFR during donor evaluation and who underwent a kidney biopsy at donation. The mean single‐nephron GFR was calculated as the GFR divided by the number of nephrons (calculated as the cortical volume of both kidneys as assessed on CT times the biopsy‐determined glomerular density). Demographic and clinical characteristics and biopsy findings were correlated with the single‐nephron GFR. RESULTS A total of 58% of the donors were women, and the mean (±SD) age of the donors was 44±12 years. The mean GFR was 115±24 ml per minute, the mean number of nephrons was 860,000±370,000 per kidney, and the mean single‐nephron GFR was 80±40 nl per minute. The single‐nephron GFR did not vary significantly according to age (among donors <70 years of age), sex, or height (among donors ≤190 cm tall). A higher single‐nephron GFR was independently associated with larger nephrons on biopsy and more glomerulosclerosis and arteriosclerosis than would be expected for age. A higher single‐nephron GFR was associated with a height of more than 190 cm, obesity, and a family history of end‐stage renal disease. CONCLUSIONS Among healthy adult kidney donors, the single‐nephron GFR was fairly constant with regard to age, sex, and height (if ≤190 cm). A higher single‐nephron GFR was associated with certain risk factors for chronic kidney disease and certain kidney‐biopsy findings. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.)