Interobserver variation in the sonographic estimation of renal volume in children

Abstract

Objective: To quantify the interobserver variability in the sonographic estimation of renal volume in children.

Materials and methods: Three observer pairs measured the lengths and diameters of 176 kidneys in 90 children. Renal volumes were estimated from the formula for a prolate ellipsoid. The mean and standard deviation of the absolute and percentage differences between observers were calculated. The 95 % limits of agreement for each pair of observers were derived. Log-transformed data were used to derive overall limits of agreement.

Results: Absolute interobserver variation increased with renal volume. Percentage variation was independent of renal size. There is a 95 % probability that a measurement of renal volume by one observer will be between 0.69 and 1.44 times a measurement made by a different observer.

Conclusion: The interobserver variation in the sonographic estimation of renal volume represents approximately 2-3 years' normal growth in children aged over 2 years.