European Radiology

, Volume 30, Issue 1, pp 206–212 | Cite as

Intraobserver and interobserver reliability in sonographic size measurements of gallbladder polyps

  • Seul Bi Lee
  • Yedaun LeeEmail author
  • Seung Jin Kim
  • Jung Hee Yoon
  • Seung Ho Kim
  • Suk Jung Kim
  • Hyun Kyung Jung
  • Seok Hahn
  • Hye Jin Baek



To evaluate the intraobserver and interobserver reliability of gallbladder polyp measurements using transabdominal US and the factors that affect reliability.


From November 2017 to February 2018, two radiologists measured the maximum diameter of 91 gallbladder polyps using transabdominal US. Intraobserver and interobserver agreement were determined using 95% Bland-Altman limits of agreement and intraclass correlation coefficients (ICCs). The effects of image settings, polyp location, and polyp size were evaluated by comparing ICCs using z tests.


The intraobserver agreement rates were 0.960 (95% confidence interval [CI], 0.939–0.973) for observer 1 and 0.962 (95% CI, 0.943–0.975) for observer 2. The ICCs between the two observers were 0.963 (95% CI, 0.926–0.979) for the first measurement and 0.973 (95% CI, 0.950–0.984) for the second measurement. The 95% limits of agreement on repeated measurements were 22.3–25.2% of the mean, and those between the two observers were 25.5–34.2% of the mean. ICCs for large polyps (≥ 5 mm) were significantly higher than those for small polyps (< 5 mm). There were no significant differences in the ICCs between image settings and polyp location.


Polyp size measurements using transabdominal US are highly repeatable and reproducible. Polyp size significantly affects the reliability of measurement. Diameter changes of approximately less than 25% may fall within the measurement error; this should be considered while interpreting the change in size during follow-up US, especially for small polyps.

Key Points

• Gallbladder polyp size measurement using transabdominal US is highly repeatable and reproducible.

• Diameter changes of approximately less than 25% should be interpreted carefully, especially in small polyps.


Gallbladder Observer variation Polyps Reproducibility of results Ultrasonography 



Confidence interval


Intraclass correlation coefficients


Limit of agreement



The authors state that this work has not received any funding.

Compliance with ethical standards


The scientific guarantor of this publication is Yedaun Lee.

Conflict of interest

The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

No complex statistical methods were necessary for this paper.

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

Institutional Review Board approval was obtained.


• retrospective

• observational

• performed at one institution


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Copyright information

© European Society of Radiology 2019

Authors and Affiliations

  1. 1.Department of RadiologyInje University College of Medicine, Haeundae Paik HospitalBusanRepublic of Korea
  2. 2.Department of RadiologySeoul National University HospitalSeoulRepublic of Korea
  3. 3.Department of RadiologyGyeongsang National University School of Medicine and Gyeongsang National University Changwon HospitalChangwonRepublic of Korea

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