Adenomyomatosis Imaging 

Differentiating between adenomyomatosis and cholesterolosis is difficult at times. Hyperplastic cholecystosis is the term used to describe cholesterolosis and adenomyomatosis. The imaging characteristics of adenomyomatosis are demonstrated in the images below.^{[1, 2, 3]}

Adenomyomatosis is a benign condition characterized by hyperplastic changes of unknown etiology involving the gallbladder wall and causing overgrowth of the mucosa, thickening of the muscular wall, and formation of intramural diverticula or sinus tracts termed Rokitansky-Aschoff sinuses. Adenomyomatosis is a common tumorlike lesion of the gallbladder with no malignant potential and may involve the gallbladder in a focal, segmental, or diffuse form.

The etiology of cholesterolosis is also unknown. Cholesterolosis is a local phenomenon unrelated to atherosclerosis. Triglycerides and cholesterol esters are deposited in the lamina propria of the gallbladder wall. Grossly, the lipid deposits are visible, lending the gallbladder wall a strawberry-like appearance—hence, the term strawberry gallbladder. The deposits vary in size and can be as large as 1 cm.

Preferred examination

Ultrasonography (US) is the preferred radiologic examination. Oral cholecystogram can be used to diagnose adenomyomatosis; however, use of ultrasonography (US) and magnetic resonance imaging (MRI) is preferred. MRI, computed tomography (CT) scanning, and positron emission tomography (PET) can be used as problem-solving modalities, especially to differentiate hyperplastic cholecystosis from gallbladder carcinoma.^{[4, 5, 6, 2, 7, 8, 9, 10, 11, 12, 13]}

Limitations of techniques

Occasionally, US cannot differentiate between the segmental type of adenomyomatosis and gallbladder carcinoma.

If Rokitansky-Aschoff sinuses are patent, oral cholecystogram demonstrates the characteristic appearance of sinuses filled with contrast. (See the image below.)

In patients with cholesterolosis, an oral cholecystogram demonstrates the larger polypoid cholesterol deposits as fixed lucencies in the opacified lumen. The deposits are distinguished from gallbladder stones by a failure to move with compression and positional change. Ultrasonography shows the lesions as nonshadowing, nonmobile intraluminal echoes.

Degree of confidence

Radiography is not the preferred choice.

CT scans of adenomyomatosis reveal a thickened gallbladder wall with the rosary sign. The rosary sign is formed by the enhanced proliferative mucosal epithelium, with the intramural diverticula surrounded by the unenhanced hypertrophied muscle coat of the gallbladder.^{[2, 8]}

Degree of confidence

Findings on CT scan usually are confirmed further by other imaging modalities. CT is useful in excluding gallbladder carcinoma.

Ching et al studied the accuracy of CT in differentiating adenomyomatosis from gallbladder cancer in a retrospective study of 36 patients with pathologically proven adenomyomatosis or gallbladder cancer who had undergone preoperative abdominal CT. The authors determined from study findings that CT is limited in the detection and differentiation of adenomyomatosis and gallbladder cancer, but the diagnosis of adenomyomatosis can be made with reasonable accuracy when thickening of the gallbladder wall is seen to contain small cystic-appearing spaces.^[2]

MRI can be used in cases that are difficult to diagnose, being well able to differentiate adenomyomatosis from cholesterolosis .^{[7, 11, 13]} Gallbladder wall thickening with multiple intramural cystic components from Rokitansky-Aschoff sinuses can be visualized readily using MRI and is considered diagnostic of adenomyomatosis.

T2-weighted MRI breath-hold sequences are superior to other sequences in visualizing Rokitansky-Aschoff sinuses.

Diffuse-type adenomyomatosis typically shows early mucosal enhancement and subsequent serosal enhancement. Localized adenomyomatosis exhibits homogeneous enhancement, showing smooth continuity with the surrounding gallbladder epithelium.

Intramural cystic formation (anechoic diverticula) with echogenic foci and/or reverberation artifacts together with full or partial thickening of the gallbladder wall are considered to be the diagnostic findings on US examination. Reverberation artifact from cholesterol crystals is V-shaped and shorter in length than artifact from air. Sometimes, the calcium present within the sinuses may give rise to twinkle artifact.

On US, diffuse or segmental gallbladder wall thickening is evident. Intramural diverticula may be seen. Diverticula containing bile are anechoic, and those containing sludge or stone are hyperechoic, with or without shadowing or reverberation artifacts.

If intramural diverticula are not identified, differentiating adenomyomatosis from other causes of gallbladder wall thickening, such as inflammation or carcinoma, is difficult. (See the images below.)

Degree of confidence

Segmental and focal adenomyomatosis may be difficult to differentiate from gallbladder carcinoma if characteristic features are not present.

Small polypoid lesions of strawberry gallbladder can be differentiated successfully from gallbladder carcinoma using PET scanning with 18-fluorodeoxyglucose (FDG). PET reveals a focus of FDG uptake at the site of gallbladder carcinoma. No focal uptake is noted in cholesterol polyps.^[14]