Ultrasound for the Detection of Gallbladder Malignancy in Primary Sclerosing Cholangitis

In primary sclerosing cholangitis (PSC), the risk for gallbladder malignancy is increased. Surveillance imaging is used for early diagnosis. The study aims to assess the reliability of ultrasound and magnetic resonance imaging (MRI) for the detection of gallbladder polyps in people with PSC and to define a polyp size as a cut-off at which cholecystectomy is indicated due to the high probability of a malignant finding.

In this retrospective European multicentre study, we included 51 people with PSC who had cholecystectomy for gallbladder polyps detected on imaging using ultrasound and/or MRI within 6 months prior to cholecystectomy and a histology report available. As a control group, we included 102 people with PSC with other indications for cholecystectomy. Malignancy was defined as high-grade dysplasia or carcinoma on histology.

Including all 153 patients, ultrasound was significantly more sensitive than MRI in detecting gallbladder polyps (p < 0.001). MRI missed 3 of the 8 malignant polyps. Malignant polyps (n = 8, median size = 12.5 mm) were significantly larger than non-malignant polyps (n = 26, median size = 6 mm) on ultrasound (p < 0.001). Ultrasound detected malignant polyps reliably (AUC = 0.91, p < 0.001) with an optimal cut-off of 8 mm. This cut-off was defined in the Hamburg cohort and validated in a multicentre validation cohort with an AUC of 0.92 (p = 0.02).

Ultrasound is more sensitive for the detection of gallbladder polyps than MRI in people with PSC. The best cut-off to differentiate between benign and malignant polyps was 8 mm. Ultrasound (gallbladder) and MRI (bile ducts) may thus be complementary methods for hepatobiliary malignancy surveillance in people with PSC.