Adenomyomatosis Imaging
Updated: Mar 18, 2018
Author: Vikram S Dogra, MD; Chief Editor: John Karani, MBBS, FRCR
Practice Essentials
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 focal type is the most common and usually involves the gallbladder fundus. Differentiating between adenomyomatosis and cholesterolosis is difficult at times. Hyperplastic cholecystosis is the term used to describe cholesterolosis and adenomyomatosis.
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.[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
Occasionally, US cannot differentiate between the segmental type of adenomyomatosis and gallbladder carcinoma.
The imaging characteristics of adenomyomatosis are demonstrated in the images below.[13, 1, 14]
Sonogram in a patient with adenomyomatosis.
Oral cholecystogram shows focal fundal thickening in a patient with focal fundal adenomyomatosis.
Radiography
If Rokitansky-Aschoff sinuses are patent, oral cholecystogram demonstrates the characteristic appearance of sinuses filled with contrast. (See the image below.)
Oral cholecystogram shows focal fundal thickening in a patient with focal fundal adenomyomatosis.
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.
Computed Tomography
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.[1, 9, 15, 16]
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.[1]
Magnetic Resonance Imaging
MRI can be used in cases that are difficult to diagnose, being well able to differentiate adenomyomatosis from cholesterolosis.[5, 9, 17, 18] Gallbladder wall thickening with multiple intramural cystic components from Rokitansky-Aschoff sinuses can be visualized readily using MRI and is considered diagnostic of adenomyomatosis.
On T2-weighted MRI imaging, the pearl necklace sign refers to multiple high-intensity cavities seen in the gallbladder wall. This pathognomonic sign carries 92–98% specificity for adenomyomatosis.[5] However, it is only present in 70% of patients, and it becomes difficult to visualize when Rokitansky-Aschoff sinuses are smaller than 3 mm or in sinuses filled with proteinaceous fluid or small stones. Magnetic resonance cholangiopancreatography (MRCP) is able to identify smaller Rokitansky-Aschoff sinuses, and the combined use of MRI and MRCP has been proposed to differentiate adenomyomatosis from gallbladder cancer in the absence of the pearl necklace sign.[19]
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.
Differentiation of echogenic intramural foci from abnormal enhancement requires a multiphasic MRI protocol with intravenous contrast material. Diffusion-weighted imaging has been found to be useful in differentiating gallbladder adenomyomatosis from gallbladder carcinoma and significantly improves the diagnostic accuracy.[20]
Ultrasonography
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.[9, 10, 11]
(See the images below.)
Sonogram in a patient with adenomyomatosis.
Transverse sonogram of the gallbladder shows multiple hyperechoic foci within the gallbladder wall with reverberation artifact. These findings are seen in patients with hyperplastic cholecystosis.
Transverse sonogram in a patient with adenomyomatosis. Gallbladder wall is thickened, and many hyperechoic foci are seen in the gallbladder wall.
Longitudinal sonogram of gallbladder shows a hyperechoic focus in the anterior wall with reverberation artifact, which is characteristic of hyperplastic cholecystosis.
Segmental and focal adenomyomatosis may be difficult to differentiate from gallbladder carcinoma if characteristic features are not present.
Contrast-enhanced ultrasound (CEUS) has been used for the diagnosis of adenomyomatosis and is considered a valuable complement to conventional US. CEUS may be useful for differentiating malignant tumors from sludge and can also differentiate cystic structures from parenchymal structures. Visualization of Rokitansky-Aschoff sinuses is increased compared to gray scale US. Two “hyper-echoic lines” around the lesion with the small nonenhancement spaces in the arterial phase of CEUS are the characteristic findings of adenomyomatosis.[21]
In a study of 105 gallbladder lesions, CEUS sensitivity was higher than that of conventional ultrasound(94.1% vs 82.4%), as well as specificity (95.5% vs 89.8%), positive predictive value (80.0% vs 60.9%), negative predictive value (98.8% vs 96.3%) and accuracy (95.2% vs 88.6%).[22]
Nuclear Imaging
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.[23] However, few reports, consisting mostly of case reports, have examined the utility of PET scan alone or in combination with 18F-labeled deoxyglucose (FDG-PET) for adenomyomatosis imaging, and no evidence exists to support the routine use of FDG-PET scan.[19]