Kidney size in relation to ageing, gender, renal function, birthweight and chronic kidney disease risk factors in a general population.

BACKGROUND: The relationship of kidney size to ageing, kidney function and kidney
disease risk factors is not fully understood.
METHODS: Ultrasound length and parenchymal kidney volume were determined from a
population-based sample of 3972 Sardinians (age range 18-100 years). We then
identified the subset of 2256 'healthy' subjects to define age- and sex-specific
reference ranges (2.5-97.5 percentile) of kidney volume. Logistic regression
(accounting for family clustering) was used to identify the clinical
characteristics associated with abnormally large kidneys or abnormally small
kidneys.
RESULTS: In the healthy subset, kidney volume and length increased up to the
fourth to fifth decade of life followed by a progressive decrease in men, whereas
there was a gradual kidney volume decrease throughout the lifespan of women. In
the whole sample, independent predictors of lower kidney volume (<2.5 percentile
for age and sex) were male sex, low body mass index, short height, low waist:hip
ratio and high serum creatinine (SCr); the independent predictors of larger
kidney volume (>97.5 percentile for age and sex) were younger age, female sex,
diabetes, obesity, high height, high waist:hip ratio and lower SCr. Estimated
heritability for kidney volume was 15%, and for length 27%; kidney volume
correlated strongly with birthweight.
CONCLUSIONS: Overall, in a general healthy population, kidney measures declined
with age differently in men and women. The determinants of kidney parenchymal
volume include genetic factors and modifiable clinical factors.