A simple ultrasonic method for assessing renal size.

The relation between renal length (L) and the distance between the first four lumbar transverse processes, (4TP) as measured by sonography and intravenous urography, has been studied in 20 adults with normal urograms. The ratio of L/4TP (Mean +/- 2.S.D.) was 1.04 +/- 0.22 for sonograms and 1.25 +/- 0.26 for urograms. The possible reasons for these differences are discussed. It is suggested that measurement of the distance between the 4TP is a simple method for estimating expected normal renal size in patients referred for renal ultrasonography.