New Ultrasound Study of Incidentally Detected Gallbladder Polyps Raises Questions About Current Guidelines

Is it time to rethink size change thresholds for incidentally detected gallbladder polyps?

In a new retrospective study presented at the American Roentgen Ray Society (ARRS) conference, researchers assessed over 9,600 patients who had at least one ultrasound exam over an 11-year period in a screening program for hepatocellular carcinoma (HCC). They identified 759 patients who were diagnosed with at least one gallbladder polyp and 434 patients had multiple ultrasound exams, according to the study.

Noting that 16.4 percent of patients had polyps that decreased in size over time, 9.7 percent of patients had polyps that increased in size over time and 22.4 percent of patients had fluctuant polyps, the researchers detected no gallbladder carcinomas in the patient cohort that had gallbladder polyps. For the 19 patients with polyps greater than 10 mm who had a subsequent cholecystectomy, there were no gallbladder carcinomas, according to the study authors.

With most guidelines advising the use of absolute polyp size or change in size over time as a key ultrasound finding for stratifying risk and appropriate management of patients with gallbladder polyps, it may be time to rethink that approach, according to study co-authors Andrew Walsh, M.D., Ph.D., an associate with MIC Medical Imaging in Alberta, Canada, and Aya Kamaya, M.D., the director of ultrasound and interim chief of the Body Imaging Division at Stanford University.

“Understanding the natural history of change in size and number of polyps over time of sonographically detected polypoid gallbladder lesions is critical in informing potential guidelines,” wrote Drs. Walsh and Kamaya in their poster presentation, which earned magna cum laude honors at the ARRS conference. “As imaging technology and resolution of ultrasound improves, size may be less of an important distinguishing feature of gallbladder polyps in the future.”

While other studies comparing first and last ultrasound exams have found that gallbladder polyps can disappear, Walsh and Kamaya said the ability to review multiple longitudinal exams in this study led to new findings with imaging of gallbladder polyps.

“Not only do polyps disappear as other studies have described but (they) can also disappear and reappear on subsequent examinations and can both increase as well as decrease in size in the same patient over multiple examinations,” explained Drs. Walsh and Kamaya.

For patients who had multiple ultrasound exams, the study authors said the average time between the first and last ultrasound was 3.6 years with the greatest amount of time between exams being 11 years. Drs. Walsh and Kamaya noted that current guidelines from the American College of Radiology (ACR) and the Canadian Academy of Radiology (CAR) recommend yearly follow-up exams for gallbladder polyps equal to or greater than 7 mm in size. European guidelines recommend follow-up ultrasound exams at one, three and five years for monitoring of polyps less than 6 mm in size in patients with no risk factors and follow-up exams at six months and yearly for up to five years for patients with risk factors, including age over 50, sessile polyp configuration and primary sclerosing cholangitis, according to Drs. Walsh and Kamaya.

In regard to study limitations, the study authors pointed out a lack of adherence to the six-month surveillance follow-up for many at-risk patients with changes in health care insurance and local employment conditions being likely contributing factors. They also noted that they focused on patients who were being monitored over time for HCC as opposed to follow-up imaging specific to gallbladder polyps. Drs. Walsh and Kamaya acknowledged a lack of clarity on whether underlying liver disease factors into a different susceptibility for gallbladder polyps and noted that other studies have found that chronic liver disease is not a risk factor for these polyps.