ARRS Case of the Week
GASTROINTESTINAL IMAGING: Biliary
Case Author: Peter S. Liu, MD, University of Michigan
History
54-year-old woman with incidental finding of abnormal gallbladder at MRI because of bladder cancer and renal transplant.
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Imaging Findings
Axial (A) and coronal (B) T2-weighted MR images of the abdomen show diffuse thickening of the gallbladder wall with numerous intramural cystic foci (arrows). Axial contrast-enhanced T1-weighted MR image (C) shows no internal enhancement of these cystic foci (arrow).
Diagnosis
Gallbladder adenomyomatosis
Teaching Points
Adenomyomatosis of the gallbladder is a benign nonneoplastic condition characterized by hyperplasia of the muscularis propria with resultant mucosal epithelium-lined intramural diverticula called Rokitansky-Aschoff sinuses.
Adenomyomatosis is found in 5–8% of gallbladder specimens, often as an incidental finding. It can variably affect the gallbladder circumference, including diffuse, segmental, and focal involvement.
Although adenomyomatosis frequently coexists with cholelithiasis, there is no documented causal relation. Because adenomyomatosis is a benign process with no inherent malignant potential, there is no requisite treatment or follow-up. Occasionally, adenomyomatosis can be implicated as a primary cause of abdominal pain, which can be relieved by cholecystectomy.
At ultrasound, adenomyomatosis should be considered in the differential diagnosis of gallbladder wall thickening. The presence of echogenic intramural foci that cause characteristic comet-tail reverberation artifacts increases specificity in the diagnosis of adenomyomatosis.
MRI shows the wall thickening of adenomyomatosis with the protruding fluid-filled RokitanskyAschoff sinuses as having high signal intensity on T2-weighted images and low signal intensity on T1-weighted images. The multiple aligned Rokitansky-Aschoff sinuses can form a string of beads or pearl necklace sign that has 92% specificity for adenomyomatosis. This feature helps differentiate adenomyomatosis from gallbladder neoplasm because the contrast enhancement patterns of the two diagnoses can overlap.
Suggested Readings
Catalano OA, Sahani DV, Kalva SP, et al. MR imaging of the gallbladder: a pictorial essay. RadioGraphics 2008; 28:135–155
Haradome H, Ichikawa T, Sou H, et al. The pearl necklace sign: an imaging sign of adenomyomatosis of the gallbladder at MR cholangiopancreatography. Radiology 2003; 227:80–88
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