Adenomyomatosis is a benign hyperplastic condition of the gallbladder consisting of hyperplasia of the gallbladder wall with hernation of mucosal epithelium into the wall. The latter results in intramural diverticula lined by epithelium, also known as Rokitansky-Aschoff sinuses. Cholesterol crystals, sludge or stones often precipitate within the bile trapped within these sinuses. Adenomyomatosis may involve the gallbladder diffusely but is usually focal, most commonly in the fundus.

Ultrasound often demonstrates non-specific gallbladder wall thickening. Small echogenic foci within the wall with V-shaped comet tail artefact, as shown in this case, represents cholesterol crystals within the Rokitansky-Aschoff sinuses. This finding, when present, is highly specific for gallbladder adenomyomatosis. Hyperechoic sludge and stones may also be seen within the sinuses in the wall.
Contrast-enhanced CT and MRI may show abnormal gallbladder wall thickening and enhancement, but this also has a differential diagnosis including polyposis, adenoma and carcinoma. However, if the Rokitansky-Aschoff sinuses are of sufficient size, they may be seen as cystic spaces within the thickened wall which suggests the diagnosis.

Gallbladder adenomyomatosis is usually an asymptomatic incidental finding but may rarely cause abdominal pain. There is no malignant potential.

Reference: Boscak AR et al, Gallbladder adenomyomatosis, Radiographics 2006;26:941-946
Credit: Dr Donna D’Souza