Teaching Case

A 28-year-old man presented with right upper quadrant pain and postprandial nausea.

MR images showed a thickened gallbladder wall and intramural cavities, which are hypointense on the T1- weighted images and hyperintense on the T2-weighted images.
This thickening was located in the fundus and extended to the body causing important luminal stenosis.

Adenomyomatosis of the gallbladder is a relatively common and benign disease that has been reported in up to 8.7% of cholecystectomy specimens [1].

It is more frequent in middle-age women and the incidence increases with age. Many patients remain asymptomatic and adenomyomatosis is an incidental finding on ultrasonography or histologic examination. Other patients present with colicky pain which cannot be distinguished from the pain caused by calculi, found in 90% of cases.

Pathologically, adenomyomatosis is one hyperplastic cholecystosis characterised by proliferation of the mucosa of the gallbladder wall, forming invaginations and diverticula, penetrating a thickened muscular layer, which results in the appearance of gland-like or cyst-like structures in the gallbladder wall: Rokitansky-Aschoff sinuses [2].

Adenomyomatosis is classified into three morphologic subtypes: diffuse, segmental, and focal. In diffuse adenomyomatosis there is diffuse mural thickening and luminal narrowing. In segmental form, there is focal circumferential stricture in the midportion of the gallbladder, producing an “hourglass” appearance. In the focal type, the lesion is usually confined to the fundus and presents as a nodule.

Ultrasonography is the method of choice in evaluating suspected gallbladder diseases. It demonstrates thickening of the gallbladder wall and anechoic intramural diverticula with or without comet-like echo representing cholesterol crystals within the lumina of Rokitansky-Aschoff sinuses, which is highly specific for adenomyomatosis [2].

In CT, adenomyomatosis findings are common but nonspecific: thickening of the gallbladder wall and intramural diverticula. Biliary sludge and calculi may be detected as high-attenuation intraluminal material. The “rosary sign” has been described, formed by enhancing epithelium within intramural diverticula surrounded by the relatively unenhanced hypertrophied gallbladder muscularis [2].

Magnetic resonance is increasingly being used in the diagnosis of adenomyomatosis. The thickened gallbladder wall appears hypointense on T2-WI and hyperintense on T1-WI. The Rokitansky-Aschoff sinuses are markedly hyperintense on T2-WI aligned spots forming the “string of beads sign” or “pearl necklace sign”, which is highly specific (92%) in diagnosing gallbladder adenomyomatosis versus gallbladder cancer [3, 4]. Intraluminal calculi may appear as signal voids due to their mineral content.

This entity should be part of the differential diagnosis in patients with biliary symptoms in order to avoid surgical procedures. Ultrasound and MRI with cholangiopancreatography have comparable sensitivity and accuracy to differentiate between adenomyomatosis and gallbladder cancer and benignity features are often present [5, 6].

Cholecystectomy by laparoscopic approach is reserved to the few patients whose symptoms are clearly connected with the imaging findings or whenever it is not possible to exclude malignancy changes.