Purpose. The aim of this study was to evaluate sonographically measure
d absolute and relative lengths of normal kidneys according to subject
height, sex, and age. Methods. Real-time sonography was performed on
202 subjects. Measurements of longitudinal renal diameter represented
absolute renal length. Relative renal length was calculated using the
kidney length: body height ratio (KBR). Results. Statistical analyses
were done on findings in 175 subjects without renal impairment (104 me
n and 71 women) whose ages ranged from 17 to 85 years (mean +/- SD, 46
.3 +/- 17.1). The mean heights of the subjects were 176 +/- 7 cm for m
en and 167 +/- 6 cm for women. The left kidney was absolutely (mean +/
- SD, 112 +/- 9 mm) and relatively (mean KBR +/- SD, 0.655 +/- 0.042)
longer than the right kidney (absolute length, 110 +/- 8 mm; KBR, 0.64
1 +/- 0.038), regardless of sex (p < 0.01). The absolute renal length
was significantly greater in men than in women for both kidneys (p < 0
.01), but there was no significant difference between KBRs (p > 0.05).
Renal length decreased with age, and the rate of decrease seemed to a
ccelerate at 60 years and older. When height and age were included in
the multivariate regression analysis, sex was not a significant predic
tor of kidney length. Conclusions. Relative renal length better repres
ents kidney size than absolute renal length because it eliminates sex
and height differences. (C) 1998 John Wiley & Sons, Inc.