Differential Diagnosis of Small Polypoid Lesions of the Gallbladder

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Abstract
To evaluate the accuracy of endoscopic ultrasonography (EUS) in making a differential diagnosis of small (≤20 mm) polypoid lesions of the gallbladder. Differential diagnosis of these lesions is often difficult using conventional imaging modalities. The findings of EUS and transabdominal ultrasonography were retrospectively analyzed in 65 surgical cases of small polypoid lesions (cholesterol polyp in 40, adenomyomatosis in 9, adenoma in 4, and adenocarcinoma in 12). Polypoid lesions exceeding 10 mm suggested malignancy. EUS showed a tiny echogenic spot or an aggregation of echogenic spots with or without echopenic areas in 95% of patients with cholesterol polyps. EUS showed multiple microcysts or comet tail artifact in all adenomyomatosis cases. Adenomas and adenocarcinomas were not associated with the echogenic spots, microcysts, or artifacts. Among adenomas and adenocarcinomas, all sessile lesions were adenocarcinomas. EUS differentiated among polypoid lesions more precisely than ultrasonography (97% vs. 71%). A tiny echogenic spot or an aggregation of echogenic spots and multiple microcysts or comet tail artifact is pathognomonic for cholesterol polyp and adenomyomatosis, respectively. Polypoid lesions without these findings indicate adenoma or adenocarcinoma on EUS. Routine use of EUS is recommended for differential diagnosis of polypoid gallbladder lesions when ultrasonography shows no signs indicative of either cholesterol polyp or adenomyomatosis.