Accuracy of repeated kidney size estimation by ultrasonography and urography in children.

The accuracy of repeated sonographic and urographic kidney length measurements in kidney size evaluation was investigated in 80 children 0 to 14 years of age, mean age 4.5 years. At sonography 250 kidney lengths were compared. A difference of 0 to 1.0 cm in repeated length measurement was considered to be good accuracy and 94 per cent of right and 96 per cent of left kidney lengths were found within this interval--a better result than for urography with 76 per cent of repeated right kidney and 79 per cent of kidney lengths within the same interval (94 lengths). Both methods display a variation of kidney length which may lead to under- and overestimation of kidney size and growth. The investigation thus indicates good accuracy for repeated sonographic kidney size assessment which should be repeated often enough to establish a growth chart displaying the trend rather than rely too much on single measurements. Sonography can be highly recommended as a convenient and harmless alternative to urography.