Changes in sizes and distensibility of the aging kidney

Age-related changes in kidney size and distensibility were examined in 103 patients aged 18 to 89 years without evidence of renal disease or hypertension. Kidney dimensions were measured on radiographs obtained 30 s and 5 min after intravenous injection of contrast agent. Kidney distension was calculated by expressing the difference in area between 30 s and 5 min films as a percentage of the area at 30 s. Distension was not significantly correlated with age but wide variation between individuals may limit the value of measurement of this change in size as a diagnostic test. After middle age, kidney length diminished by approximately 0.5 cm per decade. This reduction implies a loss of kidney weight about double that recorded at necropsy. Post-mortem evidence probably underestimates differences between age groups and age-related diminution in kidney size may be greater than post-mortem evidence suggests.