Background. Nephrocalcinosis is often associated with a variety of hypercal
cemic conditions. Diagnostic ultrasound is often used for assessing nephroc
alcinosis in children, but its reliability has not been proven.
Objective. To determine the reliability of expert interpretation of sonogra
phic films with a grading scale of severity for nephrocalcinosis.
Materials and methods. Fifty-eight ultrasonographic films of 30 children wi
th Williams syndrome and other conditions know to be associated with nephro
calcinosis were assessed. We used a blinded randomized design to assess int
ra- and interobserver reliability.
Results. Grades I, II, and III nephrocalcinosis were noted in 13%, 19%, and
27% of the examinations, respectively. The weighted kappa coefficient was
0.80 (standard error 0.12; 95% confidence interval 0.68-0.92) for intraobse
rver agreement and 0.76 (standard error 0.13; 95% confidence interval 0.63
to 0.89) for interobserver agreement. Reliability in assessing change from
one examination to the next, with independently graded films, was fair with
an unweighted kappa coefficient of 0.68 (95% confidence interval 0.38-0.96
) and 0.51 (95% confidence interval 0.21-0.80) for intra- and interobserver
reliability, respectively.
Conclusion. The severity of nephrocalcinosis can be reliably interpreted wi
th an ultrasonography grading scale.