2008 Annual Meeting Abstracts

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Background: Polypoid lesions of the gallbladder have been a common finding on ultrasound examinations of the abdomen and are more prevalent since our use of equipment incorporating pulse shaping, increased bandwidth and better phase use for image reconstruction began in 1996. Our study correlates the pre-operative ultrasonographic findings of these lesions to the surgically resected specimen with specific regard to identifying neoplastic polyps.
Methods: A retrospective review was performed of 137 patients who had a pre-operative ultrasonographic diagnosis of a polypoid lesion of the gallbladder and subsequently underwent cholecystectomy between August 1996 and July 2007 at the Mayo Clinic Rochester.
Results: 114 pseudopolyps (cholesterol polyps, inflammatory polyps and adenomyomas) and 23 true polyps (83.2% and 16.8% respectively) were identified on histopathologic analysis. 30 polyps had suspicious ultrasonographic characteristics for neoplastic changes. 26 were ≥ 10mm, 3 had vascularity and 1 demonstrated invasion. Of these, there were 21 pseudopolyps, 2 benign adenomas and 7 with neoplastic changes on final pathology (2 low grade dysplasia, 2 high grade dysplasia and 3 adenocarcinomas). 2 asymptomatic polyps, sized 6 mm and 7 mm by ultrasound, were identified pre-operatively and not regarded as suspicious but had neoplastic changes at pathology (one low grade and one high grade dysplasia). 25 patients were followed with at least two serial ultrasound examinations. Of these, 6 demonstrated polyp growth of at least 3 mm. None of these specimens demonstrated neoplastic changes. The positive predictive value and negative predictive value for ultrasound diagnosing neoplasia based on current criteria was 23% and 98% respectively with a false negative rate of 7%.
Conclusion: Histopathologic analysis of polypoid lesions of the gallbladder continues to be the gold standard to identify neoplasia. Ultrasound has been used extensively in the pre-operative management of these lesions but modern ultrasound techniques are unable to differentiate between pseudopolyps and true polyps with any certainty. We identified 2 polyps with neoplastic changes that were less than 10 mm. Therefore, we recommend decreasing the current threshold for surgical resection to 5 mm while continuing to offer cholecystectomy for lesions that demonstrate vascularity, show invasion or are symptomatic.

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