At what size does a gallbladder polyp need surgery?

A gallbladder polyp found incidentally on ultrasound is common and almost always benign. The question that follows it — whether to remove the gallbladder — is answered differently depending on which guideline the reporting radiologist and the surgeon are working from, and the two documents most likely to be applied to a patient in Korea do not agree.

The European threshold is 10 mm#

The joint guideline issued in 2022 by the European Society of Gastrointestinal and Abdominal Radiology and three partner societies recommends cholecystectomy for any polypoid lesion of the gallbladder measuring 10 mm or more, in patients fit for and accepting of surgery.

Below that size, the European guideline turns on four named risk factors: age over 60, primary sclerosing cholangitis, Asian ethnicity, and a sessile lesion — a category that includes focal gallbladder wall thickening greater than 4 mm. A polyp of 6 to 9 mm in a patient with any one of those factors is referred for surgery. Without them, it is followed by ultrasound at six months, one year, and two years.

Polyps of 5 mm or less need no follow-up at all if no risk factor is present — a change from the 2017 version of the same guideline, which had recommended surveillance.

The Korean threshold is 15 mm#

The Korean Society of Abdominal Radiology published its own recommendations in January 2025. They split the group the European guideline treats as a single surgical category. Polyps of 15 mm or more are recommended for cholecystectomy rather than ultrasound follow-up. Polyps of 10 to 14 mm are recommended for surgery only where concerning imaging features are present; without them, surgery is described as optional and continued surveillance is acceptable.

The concerning features are specific: adjacent gallbladder wall thickening, sessile morphology, and significant growth between scans.

Why the thresholds diverge#

The 10 mm figure has been in use for decades, and the evidence assembled since has not been kind to it. A systematic review and meta-analysis published in the British Journal of Radiology in 2022 pooled 82 studies covering 67,837 patients and 67,774 polyps, among which 889 cancers were reported.

At 5 mm the equivalent figure was 0.14 percent. In the subset of studies the authors judged to be of moderate quality, the risk among patients with polyps of 10 mm or less worked out at roughly 4.6 cancers per 10,000 patients.

The same authors called for research directed at better stratifying this group and at potentially raising the intervention threshold. They also recorded that only 15.6 percent of the studies they reviewed met moderate certainty standards, and that heterogeneity between studies was substantial — so the case against 10 mm rests on a body of evidence its own authors describe as generally low quality.

The disagreement about ethnicity#

One difference between the two documents bears directly on patients in Korea. The European guideline counts Asian ethnicity among its four risk factors, which would move a 6 to 9 mm polyp in a Korean patient into the surgical category on demographic grounds alone.

The Korean recommendations list the same demographic factors — age of 50 or over, Asian ethnicity, primary sclerosing cholangitis — but state that risk should not be adjusted on the basis of them, with the exception of elevated tumour markers. A Korean radiologist following the Korean document and a European radiologist following the European one would therefore reach different conclusions about the same patient and the same scan.