Ultrasound is superior to computed tomography for assessment of medullary nephrocalcinosis in hypoparathyroidism.
BACKGROUND
Nephrocalcinosis is a complication of hypoparathyroidism and other metabolic disorders. Imaging modalities include ultrasonography (US) and computed tomography (CT). Few studies have compared these modalities, and standard clinical practice is not defined.


OBJECTIVE
The objective of the study was to determine the preferred method for assessing nephrocalcinosis.


METHODS
The design of the study was a retrospective, blinded analysis.


METHODS
The study was conducted at a clinical research center.


METHODS
Twenty-two hypoparathyroid subjects and 7 controls participated in the study.


METHODS
Contemporaneous renal US and CT images were reviewed in triplicate by 4 blinded radiologists. Nephrocalcinosis was classified using a 0-3 scale with 0 meaning no nephrocalcinosis and 3 meaning severe nephrocalcinosis.


METHODS
Intraobserver, interobserver, and interdevice agreements were measured.


RESULTS
Intraobserver agreement was high, with an overall weighted kappa of 0.83 for CT and 0.89 for US. Interobserver agreement was similar between modalities, with kappas of 0.74 for US and 0.70 for CT. Only moderate agreement was found between US and CT scores, with an intermodality kappa of 0.47 and 60% concordance. Of discordant pairs, 81% had higher US scores and only 19% had higher CT scores. Of nephrocalcinosis seen on US and not CT, 45%, 46%, and 9% were grades 1, 2, and 3, respectively. Overall, US scores were higher than CT with a cumulative odds ratio (95% confidence interval) of 5.97 (2.60, 13.75) (P < .01). In controls, 100% of US ratings were 0, and 95% of CT ratings were 0.


CONCLUSIONS
US is superior to CT for assessment of mild to moderate nephrocalcinosis in patients with hypoparathyroidism. This finding, in combination with its low cost, lack of radiation, and portability, defines US as the preferred modality for assessment of nephrocalcinosis.
Division of Endocrinology and Diabetes, Children's National Medical Center, 111 Michigan Avenue NW, Washington, DC 20010-2970, USA. aboyce@childrensnational.org
Alison M
AM
Boyce
Thomas H
TH
Shawker
Suvimol C
SC
Hill
Peter L
PL
Choyke
Michael C
MC
Hill
Robert
R
James
Nancy A
NA
Yovetich
Michael T
MT
Collins
Rachel I
RI
Gafni
D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007011:Hypoparathyroidism / Q000150:complications*; D007679:Kidney Medulla / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009397:Nephrocalcinosis / Q000000981:diagnostic imaging* / Q000209:etiology; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data; D014463:Ultrasonography / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data