ACCURACY OF RENAL ULTRASOUND MEASUREMENTS FOR PREDICTING ACTUAL KIDNEY SIZE

Purpose: We attempted to evaluate the accuracy of renal ultrasound mea surements for determining actual kidney size in a growing renal unit. Materials and Methods: We evaluated 18 renal units in growing piglets weekly for 11 weeks on ultrasound. Measured parameters included length , transverse and anteroposterior dimensions, and volume. At 11 weeks f inal ultrasound measurements were obtained, animals were sacrificed an d gross specimen measurements were made. Final ultrasound dimensions a nd serial measurements were correlated with actual size. Growth charts were constructed to evaluate variability between observations. Result s: Mean difference between final ultrasound renal length and actual si ze was 3.8 mm. (correlation coefficient 0.74). Serial length measureme nts were not more accurate than isolated measurements for predicting f inal length (correlation coefficient 0.34). Volume measurement was not more accurate than renal length. Analysis of individual growth charts revealed a significant week-to-week variation. Conclusions: Error in ultrasound measured kidney length can equal 1 or more years of growth in a child. Our results show that caution should be used when incorpor ating ultrasound measurements into surgical decision making.