Adenomyomatosis is a benign condition of the gallbladder characterized by hypertrophy of muscular wall, mucosal overgrowth forming intramural diverticula or sinus tracts called Rokitansky- Aschoff sinuses .
Morphologically there are three types of Adenomyomatosis. The diffuse (generalized), segmental (annular), and the localized. Diffuse Adenomyomatosis causes thickening of muscular layer, irregularity of the mucosal surface and small cystic structures within the wall . The segmental type causes annular thickening of the gallbladder wall which can cause focal strictures. Segmental involvement of the mid body gives the appearance described as hourglass gallbladder. Localize type most commonly seen in the fundus and often called adenomyoma .
Adenomyomatosis of the gallbladder is seen in 5% of cholecystectomies. Patients can present with abdominal pain .
Oral cholecystogram can be used to diagnose Adenomyomatosis and there will be filling of Rokitansky-Aschoff sinuses with contrast material .
Ultrasound and MRI are the preferred radiological examinations. The normal gallbladder on Grey scale sonography is an anechoic fluid filled ellipsoid structure with a sharply defined wall which is predominantly Hyperechoic and measuring 3mm or less in thickness . Characteristic sonographic features in Adenomyomatosis of gall bladder are intramural cysts, echogenic foci causing reverberation artifact with full or partial thickening of the gallbladder wall. The diverticula containing bile will appear anechoic and those contain calcium or sludge will be shown as Hyperechoic foci which may or may not cause reverberation or shadowing .Focal or segmental Adenomyomatosis may simulate gall bladder carcinoma and may be difficult in differentiating .
On color Doppler sonography the focal thickening or the intramural cysts will not demonstrate any color within it. The presence of twinkling artifact will also help in the evaluation of Adenomyomatosis of the gallbladder when reverberation artifact is difficult to demonstrate or not present in grey scale sonography . On ultrasound scan the absence of cystic space, echogenic foci or the ring down artifact and the presence of vascularity within the lesion should lead to further evaluation to differentiate it from neoplasm .
CT scan Adenomyomatosis the characteristic appearance would be gall bladder wall thickening and rosary sign. Rosary sign is formed by the enhancing proliferative mucosa, intramural diverticula surrounded by the nonenhancing hypertrophied muscular coat of gall bladder wall .
MRI scan will readily demonstrate the wall thickening with Rokitansky-Aschoff sinuses which is the diagnostic finding in Adenomyomatosis of the gallbladder. And it can differentiate cholesterolosis from Adenomyomatosis as well. MRI scans in breath- hold T2W sequences has higher sensitivity in demonstrating intramural sinuses and they appear as high signal intensity areas within the thickened gallbladder wall . In diffuse Adenomyomatosis the dynamic contrast enhance MR study show early mucosal and subsequent enhancement of the serosa. In focal Adenomyomatosis, There is smooth continuity with the surrounding mucosa and the lesion [3, 6]
18FDG PET helps in differentiate Adenomyomatosis from carcinoma of the gallbladder with a higher specificity with scans done in delayed phase and comparing the Standard Uptake Values [3, 7].