The pearl necklace sign: an imaging sign of adenomyomatosis of the gallbladder at MR cholangiopancreatography.

PURPOSE: To evaluate the demonstration of the pearl necklace sign at magnetic resonance (MR) cholangiopancreatography (MRCP) in patients with proven adenomyomatosis and carcinoma of the gallbladder.

MATERIALS AND METHODS: MRCP findings and those of a combination of unenhanced and arterial phase computed tomography (CT) and arterial phase MR imaging were retrospectively compared in 29 patients who were pathologically proven to have adenomyomatosis of the gallbladder and in 18 patients with pathologically proven gallbladder carcinoma. Receiver operating characteristic (ROC) analysis was used with a five-point confidence scale. The relative sensitivity, specificity, and accuracy of each imaging modality were also calculated. The pearl necklace sign was defined on MRCP images as small round foci, with the same markedly high signal intensity as bile, within the thickened wall of the gallbladder.

RESULTS: The mean area under the ROC curve of MRCP alone and that of the combination of MRCP and arterial phase MR imaging was significantly higher than that of combined CT (unenhanced and arterial phase) and arterial phase MR imaging alone (P <.01). The relative sensitivities in the diagnosis of adenomyomatosis of the gallbladder were 24% for the combined CT, 29% for arterial phase MR imaging, 62% for MRCP, and 57% for the combination of MRCP and arterial phase MR imaging. The mean relative sensitivity, specificity, and accuracy of the pearl necklace sign on MRCP images were 62%, 92%, and 74%, respectively. In eight (28%) of 29 patients with adenomyomatosis of the gallbladder, the pearl necklace sign was not identified by all three readers on the MRCP images.

CONCLUSION: The pearl necklace sign, which indicates the presence of Rokitansky-Aschoff sinuses within the thickened gallbladder wall, was specifically detected at MRCP for adenomyomatosis of the gallbladder.