Purpose or Case Report: Ultrasound is the current modality of choice in assessing appropriate renal growth in the pediatric population, and hence establishing accurate and reliable normograms is important. Many sonographic sets of normative data on renal length and normal range limits have been created since the early 1980’s. We evaluate the consistency of mean renal length and standard deviation between these normograms. In addition, we assess the potential role of CT/MR in evaluating renal growth.
Methods & Materials: This review of the literature looks at studies dating between 1980 to 2009, each measuring mean renal length and standard deviation in healthy patients across multiple pediatric age groups ranging from 0 months to 17 years. Sample size between studies ranged from roughly 100 patients to 300 patients.

We also review the literature assessing reliability and accuracy of CT/MR in measuring mean renal length and standard deviation.
Results: The mean renal length assessed on ultrasound may vary up to 7 mm in the same age group across the different studies. When combined with variations in the standard deviation, the normal range limits for renal length significantly differ between studies.

Mean renal length obtained by CT/MR is similar to some ultrasound studies. However, the standard deviation obtained by CT/MR is significantly less than ultrasound. CT/MR measurements are more accurate and reliable, and demonstrate less inter/intraobserver variability.
Conclusions: Due to the large variability in the normal range limits between sonographic normograms, a significant subset of pediatric patients may have reported normal sized kidneys in one normogram and reported abnormal sized kidneys in another. This can result in different clinical management depending on which normogram is used. The variability between sonographic normograms is attributed to a combination of inter/intraobserver variability, measurement technique, and difference in sample size.

CT/MR may be a viable alternative to ultrasound. CT involves radiation, and when compounded over serial studies, the dose can be significantly high. MR is expensive, time-consuming, and may need general anesthesia in younger children. Nonetheless, in certain patients where accurate and reliable assessment of renal growth is needed, CT/MR may be indicated. Since measurements between CT/MR and ultrasound can be significantly different, assessing renal growth using the same modality is suggested. Formal CT/MR normograms in pediatric patients have yet to be established.